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5МИНЕРАЛОГИЯ, 2022, том8, № 1, с. 5-93
MINERALOGY (RUSSIA), 2022, volume 8, No l,pp. 5-93
МИНЕРАЛЫ И МИНЕРАЛЬНЫЕАССОЦИАЦИИ/ MINERALS AND MINERAL ASSEMBLAGES
UDK: 553.411.071:549 DOI: 10.35597/2313-545X-2022-8-1-1
MINERALOGY OF THE VORONTSOVSKOE GOLD DEPOSIT
(NORTHERN URALS)
A.V. Kasatkin', S.Yu. Stepanov2, M.V. Tsyganko3, R. Skoda', F. Nestola5, J. Plasil6, E. Makovicky7, A.A. Agakhanov', R.S. Palamarchuk8
'FersmanMineralogicalMuseum ofRAS, Leninskypr. 18/2, Moscow, 119071 Russia; [email protected] 2Institute ofGeology and Geochemistry, UB RAS, ul. Akademika Vonsovskogo 15, Yekaterinburg, 620016Russia 3MineralogicalMuseum «ShtufnoiKabinet», ul. Vatutina 17a, Severouralsk, Sverdlovsk oblast, 624480 Russia 4Masaryk University, Kotlarska 2, Brno, 61137 CzechRepublic 5Universita di Padova, 'Via Gradenigo 6, Padova, 35131 Italy 6Institute ofPhysicsASCR, v.v.i., NaSlovance 1999/2, Prague, 18221 CzechRepublic 7UniversityofCopenhagen, Ostervoldgade 10, DK-1350, Copenhagen, Denmark 8 Institute ofMineralogy, South UralsFederalResearch CenterofMineralogyand Geoecology UBRAS, Miass, Chelyabinskoblast, 456317Russia Received 18.10.2021,accepted 15.01.2022
Abstract. The Vorontsovskoe gold deposit (Northern Urals) is unique in both Russia and the world because of the diverse and original Tl-Hg-Mn-As-Sb-S mineralization. Based on the available literature and our data, we present a list of 210 minerals found at this deposit. Eight of them are new minerals discovered by the authors: vorontsovite, ferrovorontsovite, tsygankoite, gladkovskyite, luborzakite, pokhodyashinite, gungerite, and auerbakhite. In addition, 41 minerals are found for the first time in the Russian Federation and 89 minerals are new for the deposit. We defined nine major ore mineral assemblages, including seven ones related to carbonate breccias. They contain more than 70 rare sulfides, tellurides and sulfosalts, including 31, 12, and 9 minerals with Tl, Hg and Mn, respectively, as species-defining elements. The paper also describes these mineral assemblages and minerals of the Vorontsovskoe deposit.
Keywords: Vorontsovskoe deposit, Northern Urals, ore mineral assemblage, carbonate breccia, Tl-Hg-Mn sulfosalt, new mineral, first find in Russia.
For citation: Kasatkin A.V, Stepanov S.Yu., Tsyganko M.V, Skoda R., Nestola F., Plasil J., Makovicky E., Agakhanov A.A., Palamarchuk R.S. Mneralogy of the Vorontsovskoe gold deposit (NorthernUrals). Mineralogy, 8(1), 5-93. DOI: 10.35597/2313-545X-2022-8-1-1.
Introduction
The Vorontsovskoe gold deposit is located in the Krasnoturyinsk district of Sverdlovsk Oblast (Northern Urals), 0.5 km west of the settlement of Vorontsovka, 13 km south of Krasnoturyinsk and approximately 310 km north ofYekaterinburg (Figs, la, lb). The depo-
sit was discovered in 1985 and then has been a subject of prospecting and geophysical survey for several years (Gladkovsky, 2002). In 1998, it was acquired by the mining company Polymetal. Exploration of the deposit started in 1999 by northern (now 240 m deep) and southern (now 80 m deep) open pits (Figs. 2a, b). Both primary and oxidized ores are
Fig. 1. Geographical location, geological position and structure of the Vorontsovskoe gold deposit: a - position on map of Russia; b - position in structure of the Urals; c - geological scheme modified after (Vikentyev et al., 2016).
1 - East European Platform; 2-West UralianMegazone; 3 - Central Uralian Uplift; 4 - Tagil-Magnitogorsk Megazone; 5 - West Siberian Platform; 6 - Vorontsovskoe deposit; 7 - andesitic porphyrite; 8 - volcanosedimentary rocks; 9 - marble; 10 - limestone; 11 - sedimentary carbonate breccias; 12 - pyroxene-plagioclase porphyrite; 13 - diorite; 14 - quartz diorite; 15 - skarn; 16 - sampling places. Faults: I - Vorontsovsky ore-controlling thrust, II - Vorontsovsky reverse fault, III -Yuzhno-Vorontsovsky fault, IV - Yuzhno-Peschansky fault.
stocked at the ore stockpile near the northern open pit (Fig. 2c), from where the ore is transported to the processing plant located 6 km to the east. The ore is processed by carbon-in-leach (950 Ktpa) and a seasonal heap leach circuit (1000 Ktpa). Waste dumps (Fig. 2d) and off-balance ore stockpiles (Figs. 2e, 2f) are located near the open pits. The location of the main sampling sites of the deposit is shown in Fig. lc.
Ore processing and gold production at the Voront-sovskoe deposit were maximum in 2010 (5.3 t Au) gradually decreasing to 3.71 in 2017 and 3.3 t in 2019. Dating at January 1, 2020, the ore reserves of the deposit were estimated at8.8Mt with an average Au and
Ag grade of 1.5 and 3 g/t, respectively (www.polyme-talinternational.com). In 2018 and the middle of 2020, Polymetal company ended the exploration campaign of the southern and northen open pits, respectively. Thus, the plant is currently processing the ore from the previously accumulated off-balance ore stockpiles.
Despite the 35-year history and the status of one of the largest deposits in the Northern Urals, no systematic studies of mineralogy of the Vorontsovskoe deposit have been conducted. Most published data on the deposit concern the features of its geological setting with sketchy mineralogical information. The main aim of this work is to fill this «mineralogical» gap. Using pub-
Fig. 2. Main sites of the mine operating at the Vorontsovskoe deposit:
a - northern open pit; b - southern open pit; c - main ore stockpile; d - dumps of northern open pit; e - off-balance ore stockpile no. 1; f-off-balance ore stockpile no. 2.
Photo: A.V. Kasatkin (a-d), S.Yu. Stepanov (e), M.V. Tsyganko (f).
lished and our data, we composed a list of mineral species of the Vorontsovskoe deposit and provided their mineralogical description, as well as the brief history of the study of the deposit and its geological setting. The description is provided in an alphabetical order on the basis of mineralogical classification. The isostructural minerals (e.g., minerals of the vorontsovite-fer-rovorontsovite or dalnegroite-chabourneite series, the members of the apatite supergroup, amphiboles, pyroxenes, etc.) are described together. Most new data result from materials of field trips of 2013-2021 to the open pits, dumps, main ore stockpile and off-balance ore stockpiles and laboratory studies of samples. Most
attention is paid to carbonate breccias with extremely rich and diverse Tl-Hg-Mn-As-Sb-S mineralization including numerous rare sulfides and, especially, sulfo-salts (both sulfarsenites and sulfantimonites).
Analytical studies of specimens coupled with their detailed observations and systematic documentation in situ allowed us to establish nine mineral assemblages with species-defining Tl, Hg, Pb, Cu, and/or Mn. Eight minerals (vorontsovite, ferrovorontsovite, tsygankoite, gladkovskyite, luborzâkite, pokhodyashinite, gunger-ite, and auerbakhite) are new minerals approved in 2016-2020 by the Commission on New Minerals, Nomenclature and Classification of the International Min-
eralogical Association (CNMNC IMA). Along with clerite (Murzin et al., 1996), the total amount of new minerals discovered at the Vorontsovskoe deposit is nine, which is lower than at the Lengenbach deposit in Switzerland (44) and the Allchar deposit in North Macedonia (11), two further deposits famous for their Tl-Hg-As-Sb mineralization. By the amount of minerals with species-defining T1 (31), the Vorontsovskoe deposit is only slightly behind the Lengenbach deposit (33 minerals), but is almost twice ahead of the Allchar deposit (16 minerals). By the total amount of reliable mineral species, the Vorontsovskoe deposit is certainly the richest: 210 mineral species at Vorontsovskoe versus 160 at Lengenbach (Raber, Roth, 2018) and 85 at Allchar deposits (Boev et al., 2012; www.mindat.org). A distinctive feature of the Vorontsovskoe deposit is the Mn enrichment of some mineral assemblages: Mn is a species-defining element of numerous sulfosalts and it also forms rare oxides and hydroxides, which are found in the oxidation zone of the deposit.
The following symbols of minerals are accepted in the paper: Akt, aktashite; Alb, alabandite; And, an-dorite; Apt, fluorapatite; Apy, arsenopyrite; Ars, native arsenic; As2O3, arsenolite/claudetite; Au, native gold; Bar, baryte; Bin, boulangerite; Bnl, benleonardite; Brn, bernardite; Bsc, boscardinite; Cal, calcite; Ccp, chal-copyrite; Chb, chabourneite; Chr, christite; Cln, clino-chlore; Clr, clerite; Cnb, cinnabar; Col, coloradoite; Cpb, cupropolybasite; Dfr, dufrenoysite; Din, dalne-groite; Dol, dolomite; Dps, diopside; Dur, duranusite; Dwt, dewitite; Ecr, ecrinsite; Fvr, ferrovorontsovite; Gal, galena; Gcr, geocronite; Gil, gillulyite; Gld, glad-kovskyite; Gtr, guettardite; Htr, heteromorphite; Hut, hutchinsonite; Hwl, hawleyite; Imh, imhofite; Jlp, jal-paite; Jos,joseite-A; Lbr, luborzakite; Lit, laffittite; Lor, lorandite; Mgt, magnetite; Mtc, metacinnabar; Orp, orpiment; Oyn, oyonite; Qtz, quartz; Pav, pavonite; Phi, philrothite; Pic, picotpaulite; Pkd, pokhodyashin-ite; Plb, polybasite; Pig, plagionite; Prn, prehnite; Prp, parapierrotite; Pyr, pyrite; Rbl, rebulite; Rig, realgar; Rmd, ramdohrite; Rsh, roshchinite; Rtr, routhierite; Sic, sicherite; Sin, sinnerite; Sms, semseyite; Sph, sphalerite; Stb, stibnite; Tdm, tetradymite; Thr, thorite; Til, tilasite; Tnt, tennantite; Tsg, tsygankoite; Tsn, tsni-griite; Twn, twinnite; Ves, vesuvianite; Vik, vikingite; Vor, vorontsovite; Vrb, vrbaite; Wkb, wakabayashilite; Wsb, weissbergite; Znk, zinkenite.
Vorontsovskoe deposit: history of study
The Vorontsovskoe deposit was discovered as a result of prospecting for primary gold in the Peschan-sko-Vorontsovskoe quartz vein ore field in the mid-1980s by Boris Aleksandrovitch Gladkovsky, a chief geologist of the Vorontsovskoe Geological Survey. In 1985, the karst deposits were trenched 200 m behind the road to the Shikhan recreation center, whereas due to limited funding, previous geochemical and geophysical prospecting for gold was carried out only in a narrow strip of this road along with the western contact of the Auerbakh diorite intrusion. The channel sampling of the trench showed a high Au content and, as a result, several boreholes were drilled near the trench, which exposed primary gold sulfide ores (Vikentyev et al., 2016). The prospecting works of 1985-1987 showed that the exploration of the deposit is profitable by open pit (Gladkovsky, 2002) and were followed by the detailed exploration of the deposit in 1988-1999. The detailed history of the discovery of the deposit and its geological study can be found in a few publications (Kabanov, 2001; Gladkovsky, 2002; Bobrov, 2013; Vikentyev et al., 2016).
First mineralogical studies of the deposit during its exploration were carried out in 1988-1992 by geologists of the Institute of Geology and Geochemistry, Urals Branch, Academy of Sciences of the USSR (Murzin, Sazonov, 1990; Sazonov et al., 1990a, b; Murzin et al., 1990; Grigoriev et al., 1991; Sazonov et al., 1991a, b; Ryabinin et al., 1992). The most detailed data of these studies are published in a monograph (Sazonov et al., 1991a). The monograph describes the geological structure of the ore region and ore complexes and provides a geological and genetic model of the deposit, which was referred for the first time to as Carlin-type gold deposits. The monograph also reports on mineral assemblages of various ore types with a description of minerals identified on the basis of chemical, X-ray diffraction, and optical data. Authors mentioned the presence of numerous rare minerals of the Tl-As-Sb-S and Pb-Tl-As-Sb-S systems, however, only routhierite was studied in detail. Although the authors mainly focused on geological features of the deposit (which was unnamed because of the restrictions on publication of data on gold deposits at that time) and had limited drillcore material for the study, this monograph can be considered the first fundamental mineralogical publication on the Vorontsovskoe deposit. In 1991, V.V. Mur-zin described benleonardite, a rare Ag sulfosalt found at the deposit (Mineralogy..., 1991).
The publications of the 1990s were mainly devoted to the geological and geochemical features of the deposit (Savel'eva, Kostromin, 1991; Savel'eva et al., 1991; Baryshev et al., 1993; Sazonov et al., 1993; Minina, 1994; Isakovich, 1996; Cheremisin, Zlotnik-Khotkevich, 1997; Rakhov, 1999) and only a few papers addressed particular mineralogical issues, i.e., micas (Sazonov et al., 1995) or morphology of quartz injasperoids (Begetnev, 1998). The oxidation zone of the deposit was described by N.M. Rindzyunskaya et al. (1995a, b) and A.A. Kabanov (2001), however, wi-thouth detailed study of supergene minerals.
In 1996, the new mineral clerite, MnSb2S4, was found at the deposit (Murzin et al., 1996). Murzin and Sustavov (1997) suggested the presence of new minerals in the Mn-As-Sb-S, Tl-As-Sb-S, K-As-Sb-S, and As-S systems, but indicated difficulties of their studies due to small sizes and a limited amount of the available material. Sazonov et al. (1998) reported for the first time on S isotopic composition of pyrite, sphalerite, and chalcopyrite of the deposit, as well as O and C of carbonates ofhost rocks.
The microprobe studies of the late 2000s resulted in the analysis of chemical data on minerals of a gold-sulfide-sulfosalt paragenesis of ore breccias (Murzin, Varlamov, 2010). A paragenesis of native arsenic and arsenopyrite was described by Murzin et al. (2011) and feldspars of the deposit were characterized by Rov-nushkin et al. (2010).
In 2016,1.V. Vikentyev and co-authors published a monograph that was focused on the geology and genesis of the deposit based on the results of thermobaro-metric and isotopic-geochemical studies of ores. These authors described the mineral assemblages of primary and supergene ores providing numerous reflected light and SEM images and the sequence of mineral formation; they also presented new (including LA-ICP-MS and elemental mapping) data on chemical composition of native gold, as well as of a number of main and selected rare ore minerals.
Analytical data on several ore minerals in the matrix of gold-bearing breccias are given by Stepanov et al. (2017). Mineralogy of gangue carbonates of the deposit is studied by Soroka et al. (2017, 2018). Recent publications summarize the results of previous studies of geology, mineralogy, geochemistry and geochrono-logy of the deposit (Murzin et al., 2017; Vikentyev et al., 2019). The latter paper provides a list of 76 ore minerals of the deposit. Thus, previous publications on the Vorontsovskoe deposit were mostly focused on its geology rather than on its mineralogy mainly due
to limited analytical resources that prevented from detailed studies of minerals (especially, rare, and pm-sized).
In this paper, we summarize the results of our systematic mineralogical studies of the deposit from 2013 using a multimethodological approach. As a result, 210 mineral species are identified at the deposit including eight new minerals, 41 minerals found for the first time at the territory of the Russian Federation and 89 minerals found for the first time at the deposit. New analytical data are provided for 58 minerals (Table 1). Eight new mineral species include vorontsovite and ferrovorontsovite (Kasatkin et al., 2018a), tsygankoite (Kasatkin et al., 2018b), gladkovskyite (Kasatkin et al., 2019), luborzakite (Kasatkin et al., 2020a), pok-hodyashinite (Kasatkin et al., 2022b), gungerite (Kasatkin et al., 2020c, 2022a), and auerbakhite (Kasatkin et al., 2021). Special attention was paid to the study of crystal structure of sulfosalts. The structures of natural parapierrotite (Plasil et al., 2018) and a Pb-free end-member of the chabourneite homeotypic group (Mako-vicky et al., 2021) were refined on a material from the Vorontsovskoe deposit. The latter was subsequently approved as a new mineral dewitite (Topa et al., 2021b).
Part of our data is published in papers that describe new minerals found at the deposit (Kasatkin et al., 2018a, 2018b, 2019, 2020a), also providing information on relevant mineral assemblages and analytical data on a number of rare sulfosalts. The findings of ar-menite, chapmanite, claudetite, getchellite, and waka-bayashilite are briefly characterized in a review by Kasatkin (2019). Reliable analytical data for picotpaulite, weissbergite, dalnegroite, christite, and philrothite presented here for the first time enable us to consider their first findings at the territory of the Russian Federation.
Geological setting, structure and genetic type of the deposit
The Vorontsovskoe deposit in the Northern Urals is located in the eastern part of the Tagil volcanic zone (Fig. lb) within a longitudinal volcanoplutonic belt (Sazonov et al., 1998; Murzin et al., 2017). This belt formed as a result of a collision of the Tagil island arc with the East Uralian microcontinent (Yazeva et al., 1991; Sazonov et al., 1998). The Middle Devonian Auerbakh gabbro-diorite-granodiorite pluton (Kras-nobaev et al., 2007) occurs in the southern part of the volcanoplutonic belt and its formation was related to the Auerbakh ore region.
Minerals of the Vorontsovskoe deposit
Table 1
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Mineral Fonnula Distribution ID method Source
Elements
Native arsenic* As +++++ EMPA, XRD, 0 Sazonov et al., 1991a; Murzin et al., 2011; Vikentyev et al., 2016; our data
Native copper Cu ++ 0 Vikentyev et al., 2016
Native gold* Au +++++ EMPA, 0 Sazonov et al., 1991a; Mur/in. Varlamov 2010; Murzin et al., 2011; Vikentyev et al., 2016; our data
Native silver1** Ag ++ EMPA, 0 Vikentyev et al., 2016; our data
Sulfides, arsenides, tellurides
Acanthite** Ag.S ++ EMPA, 0 our data
Alabandite* MnS +++ EMPA, XRD, 0 Sazonov et al., 1991a; Mur/in. Varlamov 2010; Murzin et al., 2011; Vikentyev et al., 2016; our data
Arsenopyrite* FeAsS +++++ EMPA, XRD, 0 Sazonov et al., 1991a; Murzin et al., 2011; Vikentyev et al., 2016; our data
Bismuthinite** Bi2S3 ++ EMPA, 0 our data
Bornite* Cu5FeS4 +++ EMPA, 0 Vikentyev et al., 2016; our data
Chalcopyrite* CuFeS, +++++ EMPA, XRD, 0 Sazonov et al., 1991a; Vikentyev et al., 2016;
Cinnabar* HgS ++++ EMPA, XRD, 0 our data
Coloradoite* HgTe +++ EMPA, XRD, 0 Sazonov et al., 1991a; Mur/in. Varlamov 2010; our data
Covellite* CuS (++) EMPA, XRD, 0 Vikentyev et al., 2016; our data
Cubanite** CuFe2S3 + EMPA, 0 our data
Dimorphite ? As4S3 ? EMPA Stepanov et al., 2017
Djurleite** cu31s16 (++) EMPA, XRD, 0 our data
Duranusite *** As4S ++ EMPA, 0
Galena* PbS +++ EMPA, XRD, 0 Sazonov et al., 1991a; Vikentyev et al., 2016; our data
Gersdorfite* NiAsS ++ EMPA, 0 Vikentyev et al., 2016; our data
Getchellite*** AsSbS, +++ EMPA, XRD, 0 Kasatkin, 2019; our data
Greigite* Fe2+Fe3+,S4 +++ EMPA, XRD, 0 Murzin et al., 1996; Murzin, Varlamov 2010; our data
Hawleyite** CdS (++) EMPA, XRD, 0 our data
Hessite1** AfcTe ++ EMPA, 0 Sazonov et al., 1991a; our data
Ikunolite** Bi4S, ++ EMPA, 0
Jalpaite** Ag,CuS2 ++ EMPA, 0 our data
Joséite-A** Bi4TeS2 ++ EMPA, 0
Löllingite* FeAs, +++ EMPA, XRD, 0 Vikentyev et al., 2016; our data
Metacinnabar** HgS +++ EMPA, XRD, 0
Molybdenite1** MoS, ++ EMPA, 0
Orpiment* As2S3 +++++ EMPA, XRD, 0 Sazonov et al., 1991a; Mur/111. Varlamov 2010; Vikentyev et al., 2016; our data
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Para real gar*** AS,S4 ++ EMPA, XRD, 0 our data
Picotpaulite1*** TlFe2S3 ++ EMPA, 0 Vikentyev et al., 2016; our data
Pyrite* FeS2 EMPA, LAICP Sazonov et al., 1991a; Murzin. Varlamov, 2010;
MS, XRD, 0 Vikentyev et al., 2016; our data
Pyrrhotite Fei-xS +++ EMPA Sazonov et al., 1991a; Vikentyev et al., 2016
Realgar* AsS +++++ EMPA, XRD, 0 Sazonov et al., 1991a; Murzin Varlamov, 2010; Vikentyev et al., 2016; our data
Sazonov et al., 1991a; Murzin, Varlamov, 2010;
Sphalerite* ZnS +++++ EMPA, XRD, 0 Murzin et al., 2011; Vikentyev et al., 2016; Stepanov et al., 2017; our data
Stibnite* Sb2S3 +++++ EMPA, XRD, 0 Sazonov et al., 1991a; Murzin Varlamov, 2010; Vikentyev et al., 2016; our data
Tetradymite** Bi,Te,S ++ EMPA, 0 our data
Wakabayasliilite* * (As,Sb)6As4Si4 +++ EMPA, XRD, 0 Kasatkin, 2019; our data
Sulfosalts
Sazonov et al., 1991a; Mineralogy of Urals, 1991;
Aktashite* Cu6Hg,As4Si2 ++++ EMPA, XRD, 0 Murzin, Varlamov, 2010; Vikentyev et al., 2016; Stepanov et al., 2017; our data
Andorite* AgPbSb,S6 ++ EMPA, 0 Vikentyev et al., 2016; our data
Argentotetrahedrite-(Fe) Ag6(Cu4Fe2)Sb4S13 ++ EMPA Sazonov et al., 1991a
Argentotetrahedrite-(Zn) Ag6(Cu4Zn2)Sb4Si3 ++ EMPA
Arsiccioite*** AgHg2TlAs2S6 + EMPA, 0 our data
Auerbakhite* * * * MnTl2As2S5 ++ EMPA, XRD, 0, RS Kasatkin et al., 2020d
Benavidesite*** Pb4MnSb6Si4 ++ EMPA, 0 our data
Benleonardite* Ag15Cu(Sb,As)2S7Te4 ++ EMPA, 0 Mineralogy of Urals, 1991; our data
Bernardite*** T1As5S8 ++ EMPA, XRD, 0 our data
Bernarlottiite ? Pb12(As10Sb6)S36 ? EMPA Vikentyev et al., 2016
Boscardinite*** AgTl3Pb4(Sb14As6)S20S36 +++ EMPA, XRD, 0 our data
Boulangerite* Pb5Sb4Sn +++ EMPA, XRD, 0 Sazonov et al., 1991a; Vikentyev et al., 2016; our data
Bournonite* PbCuSbS, ++ EMPA, XRD, 0 Sazonov et al., 1991a; Vikentyev et al., 2016; our data
Chabourneite* AgzTl8.x.zPb4 + 2xSb4o-x-yAsyS68 ++++ EMPA, XRD, 0 Murzin, Varlamov, 2010; Vikentyev et al., 2016; Makovicky et al., 2021; our data
Chalcostibite CuSbS, ++ EMPA Sazonov et al., 1991a; Vikentyev et al., 2016
Cliristite1*** TIHgAsS, +++ EMPA, XRD, 0 Vikentyev et al., 2016; our data
Clerite* MnSb,S4 ++ EMPA, XRD, 0, H Murzin et al., 1996; Murzin, Varlamov, 2010; our data
Cupropolybasite* * * rCu6Sb2S7irAg„CuS4l ++ EMPA, 0 our data
Dalnegroite1*** Tl4Pb2(As,Sb)0„S,, ++++ EMPA, XRD, 0 Vikentyev et al., 2016; our data
Dewitite*** Ag Tlio-x-zPb, Sb„ As S,„ oz 1 u A z. 2x 42-x-y y 68 ++ EMPA, XRD, 0 described by Makovicky et al., 2021 as a «lead-free end-member of the chabourneite homeotypic family» Topa et al., 2021b
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Mineral Formula Distribution ID method Source
Drechslerite*** Tl,(Sb4.vAsv)S8; 1 < x < 2 ++ EMPAO our data
Dufrenoysite** Pb0As0S. + EMPAO
Ecrinsite*** AgTl3Pb4(ASllSb9)S2oS36 +++ EMPA, XRD, 0
Enargite ? CiiiAsS, ? EMPA Vikentyev et al„ 2016
Enneasartorite * * * Tl(sPb32AS7oSl40 + EMPAO our data
Ferrovorontsovite* * * * (Fe5Cu)S6TlAs4S12 +++ EMPA, XRD, H, 0 Kasatkin et al„ 2018a; Kasatkin, Pautov, 2020
Galkhaite** (Hg5Cu)S6CsAs4S12 + EMPA our data
Geocronite* Pb14Sb6S23 ++ EMPAO Sazonov et al., 1991a; Vikentyev et al., 2016; our data
Gladkovskyite* * * * MnTlAs3S6 +++ EMPA, XRD, H, O RS Kasatkin et al., 2019
Guettardite*** PbAsSbS4 +++ EMPAO described by Vikentyev et al., 2016 as «twinnite», our data
Guillulyite*** H2As7.5Sbo.3S13 ++ EMPA, XRD, 0, RS our data
Gungerite**** TlAs5Sb4Si3 +++ EMPA, XRD, H, O RS Kasatkin et al., 2020c, 2022a
Heptasartorite*** Tl7Pb22AS55Sl08 + EMPAO our data
Heteromorphite * * * Pb7Sb8Si9 ++ EMPAO
Hutcliinsonite * * * TlPbAs5S9 ++ EMPA, XRD, 0, RS
Iinliofite*** Tl5.8As15.4S26 ++ EMPA, XRD, 0
Jamesonite* Pb4FeSb6Si4 +++ EMPA, XRD, 0 Sazonov et al., 1991a; Vikentyev et al., 2016; our data
Jordanite** Pbi4(As,Sb)6S23 + EMPA our data
Laffittite*** AgHgAsS3 ++ EMPAO
Lillianite** Pb3-2xAgxBi2+xS6 ++ EMPAO
Lopatkaite Pb5Sb3AsS„ ++ EMPA described by Vikentyev et al., 2016 as «As-bonlangerite»
Lorandite*** T1ASS2 ++ EMPA, XRD, O, RS our data
Luborzakite**** Mn2AsSbS5 ++ EMPA, XRD, H, 0 Kasatkin et al., 2020a; our data
Manganoquadratite * * * AgMnAsS, + EMPAO our data
Menegliinite** PbnCuSb7S24 ++ EMPA, XRD, 0
Nowackiite*** Cu6Zn3As4Si2 + EMPA
Oyonite*** Ag,MmPb4Sb7As4S74 + EMPAO
Parapierrotite*** TlSb5S8 ++++ EMPA, XRD, 0 Plasil et al., 2018; our data
Pavonite** AgBi,S5 ++ EMPAO our data
Pliilrotliite1*** TIAS3S5 ++ EMPA, XRD, 0 Vikentyev et al., 2016; our data
Pierrotite ? Tl2(SbAs)i0Si6 ? EMPA Sazonov et al., 1991a; Murzin, Varlamov, 2010
Plagionite* Pb5Sb8Si7 ++ EMPAO Sazonov et al., 1991a; our data
Pokhodyashinite* * * * Cu2Tl3Sb5As2Si3 ++ EMPA, XRD, H, 0 Kasatkin et al., 2022b
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Polybasite** iAg9CuS4ïï(Ag,Cu)6(Sb,As)2S7l ++ EMPAO our data
Ramdohrite** Pb6Ag3SbuS24 + EMPA
Rebulite*** Tl5Sb5As8S22 ++ EMPA, XRD, 0, RS
Roshcliinite*** (Ag,Cu)19Pb10Sb51S96 + EMPAO
Routliierite* CuHg2TlAs2S6 ++++ EMPA, XRD, 0, H Sazonov et al., 1991a; Mineralogy of Urals, 1991; Murzin, Varlamov, 2010; Vikentyev et al., 2016; Stepanov et al., 2017; our data
Semseyite** Pb9Sb8S2i ++ EMPAO our data
Sicherite*** TlAg2(As,Sb)3S6 + EMPAO
Sinnerite** Qi6As4S9 + EMPAO
Stalderite*** TlCu(ZnFe,Hg)2As2S6 + EMPAO
Tennantite-(Fe)* Cu6rCu4Fe2lAs4Si2S +++ EMPAO Sazonov et al., 1991a; Murzin et al., 2011; Vikentyev et al., 2016; our data
Tennantite-(Zn)* Cu6rCu4Zn2lAs4Si2S +++ EMPA, XRD, 0
Tetrahedrite-(Fe)* Cu6[Cu4Fe2]Sb4Si2S +++ EMPAO Sazonov et al., 1991a; our data
Tetrahedrite-(Zn)* Cu6[Cu4ZigSb4Si2S ++++ EMPAO Sazonov et al., 1991a; Murzin et al., 2011; Vikentvevet al.. 2016: our data
Tsnigriite** Ag9SbTe3S3 ++ EMPAO our data
Tsygankoite**** Mn8Tl8Hg2(Sb21Pb2Tl)S24S48 +++ EMPA, XRD, H, 0 Kasatkin etal., 2018b
Twinnite*** Pb(Sb„.63As„.37)2S4 ++ EMPA, XRD, 0 our data
Veenite*** Pb2(Sb,As)2S5 ++ EMPAO Vikentyev et al., 2016; our data
Vikingite** Ag5Pb0BipS,„ ++ EMPAO our data
Vorontsovite* * * * (Hg5 Cu)S6Tl As4 S12 ++++ EMPA, XRD, H, 0 Kasatkin et al., 2018a; Kasatkin, Pautov, 2020
Vrbaite*** Hg3Tl4As8Sb2S2„ +++ EMPA, XRD, 0 our data
Weissbergite1*** TISbS, ++ EMPA, XRD, 0 Vikentyev et al., 2016; our data
Zinkenite* Pb9Sl?22S42 +++ EMPA, XRD, 0 Sazonov et al., 1991a; Vikentyev et al., 2016; our data
Halides
Bismoclite** BiOCl (+) EMPA our data
Oxides and hydroxides
Akhtenskite** MnO, (++) EMPA, XRD our data
Arsenolite1** As203 (+++) EMPA, XRD Murzin et al., 2011; Vikentyev et al., 2016; our data
Asbolane** (Ni, C0)2.xMn+(0,0H)4 • nH20 (++) EMPA, XRD our data
Birnessite** (Na,KCa)06(Mn4+,Mn3+)2O41.5H2O (++) EMPA, XRD
Bixbyite** Mn3+,03 (++) EMPA, XRD
Cesàrolite** PbMn4+,06(0H)2 (++) EMPA, XRD
Cliromite** FeCr204 ++ EMPA
Claudetite*** As203 (+++) EMPA, XRD Kasatkin, 2019; our data
Coronadite** Pb (Mn4+6Mn3+2)S8016 (+++) EMPA, XRD our data
Cryptomelane** K(Mn4+7Mn3+)016 (+++) EMPA
Ferberite** FeW04 + EMPAO
Fergusonite-( Y) * * YNb04 + EMPA
Geikielite** MgTiO, + EMPA
Goetliite* FeOOH Í+++++1 EMPA, XRD Sazonov et al., 1991a; our data
Hematite* Fe203 Í+++++1 EMPA, XRD
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Mineral Formula Distribution ID method Source
Hollandite** Ba(Mn4+6Mn3+2)Oi6 (++) EMPA, XRD our data
Litliiophorite** (Al,Li)(Mn4+,Mn3+)0,(0H), (++) EMPA, XRD
Magnesiochromite* * MgCr204 ++ EMPA
Magnetite* Fe2+Fe3+204 +++++ EMPA, XRD Vikentyev et al., 2016; our data
Manganite** Mn3+0(0H) ++ EMPA, XRD our data
Manjiroite** Na(Mn4+7Mn3+)Oi6 (++) EMPA, XRD
Pyrolusite1** MnO, +++ EMPA, XRD Kabanov, 2001; our data
Pyroplianite** MnTiO, + EMPA our data
Quartz* SiO, +++++ EMPA, XRD, 0 Sazonov et al., 1991a; our data
Ramsdellite*** MnO, ++ EMPA, XRD our data
Ranciéite** (Ca,Mn2+)0 2(Mn4+,Mn3+)06 0.6H20 (++) EMPA, XRD
Romanécliite** (Ba,H2O)2(Mn4+,Mn3+)5Oi0 (+++) EMPA, XRD
Rutile* TiO, +++ EMPA, 0 Murzin, Varlamov, 2010; our data
Todorokite** (Na,K,Ca,BaSr)1.x(MnMg,Al)6012 • 3-4H20 (+++) EMPA, XRD our data
Vernadite1* (MuFe,Ca,Na)(0,0H)2nH20 (++++) EMPA, XRD Sazonov et al., 1991a; our data
Carbonates
Azurite** Cu3(C03)2(0H)2 EMPA, XRD our data
Calcite* CaC03 +++++ EMPA, XRD, LA ICP MS Sazonov et al., 1991a; Vikentyev et al., 2016; Soroka et al., 2017, 2018; our data
Cerussite** PbC03 EMPA, RS our data
Dolomite* CaMg(CO,)2 +++++ EMPA, XRD, LA ICP MS Sazonov et al., 1991a; Vikentyev et al., 2016; Soroka et al., 2017, 2018; our data
Kutnohorite** CaMn(CO,), ++ EMPA, XRD our data
Malacliite** Cu2C03(0H)2 (+++) EMPA, XRD
Rhodoclirosite** MnCO, +++ EMPA, XRD
Siderite* FeCO, +++ CH, EMPA, XRD Sazonov et al., 1991a; our data
Sulfates
Angle site** PbS04 (++) EMPA, XRD our data
Baryte* BaS04 +++++ EMPA Vikentyev et al., 2016; our data
Beaverite-(Cu)** Pb(Fe3+2Cu)(S04)2(0H)6 (++) EMPA, XRD our data
Brochantite** Cu4(S04)(0H)6 (++) EMPA, XRD
Chalcanthite** CuS04-5H20 (++) EMPA, XRD
Epsomite** MgS0,-7H20 (+++) EMPA, XRD
Gypsum** CaS04-2H20 (+++) EMPA, XRD
Pentahydrite** MgS04-5H20 (++) EMPA, XRD
Starkeyite** MgS04-4H20 (++) EMPA, XRD
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Scheelite** CaWO, +++ EMPA, 0 our data
Phosphates, arsenates
Bayldonite** Cu3PbO(AsO,OH)2(OH)2 EMPA, XRD our data
Chernovite-(Y)** YAs04 + EMPA
Clilorapatite** Ca5(P04)3Cl ++ EMPA
Fluorapatite* Ca5(P04),F ++++ EMPA Murzin Varlamov, 2010; Murzinet al., 2011; our data
Gasparite-(La)** LaAs04 + EMPA our data
Hydroxy lapatite* * Ca5(P04),(0H) ++ EMPA
Svabite** Ca5(As04),F + EMPA
Tilasite** CaMg(As04)F ++ EMPA, XRD, 0
Turneaurite** Ca5(As04),Cl ++ EMPA
Vivianite Fe2+3(P0,)2-8H20 +++ CH, XRD Sazonov et al., 1991a
Silicates
Albite* NaAlSi,Os +++ CM, XRF, EMPAXRD Sazonov et al., 1991a; our data
Andradite** Ca3Fe3+2[Si04]3 ++++ EMPA our data
Armenite*** BaCa2Al6Si9O30 • 2H20 +++ EMPA, XRD, 0 Kasatkin, 2019; our data
Augite** (Ca,Mg,Fe)2Si206 ++ EMPA our data
Beidellite (Na.Ca)0,Al,(Si.Al)4O10(OH),-nH,O I+++I CH, XRD Sazonov et al., 1991a
Celadonite** KMgFe3+Si,Oin(OH). +++ EMPA, XRD our data
Chabazite-Ca** Ca.Al,SiA,13H.O +++ EMPA, XRD
Chamosite* (Fe2+,Mg,ALFe3+)6(SiAl)4O10(OH,O)s +++ EMPA, XRD, 0 Sazonov et al., 1991a; our data
Chapmanite*** Fe3+,Sb3+rSi04l,(0H) (+++) EMPA, XRD Kasatkin, 2019; our data
Cliry sotile-20rrf * * Mg3Si205(0H)4 +++ EMPA, XRD our data
Clinochlore* Mg5Al2Si3O10(OH)8 +++++ EMPA, XRD, 0 Sazonov et al., 1991a; our data
Dickite** Al2Si205(0H)4 I+++I EMPA, IR our data
Diopside* CaMgSi206 ++++ EMPA Sazonov et al., 1991a; our data
Epidote Ca, ALFe3+rSi,07l |Si0,|0(0H) ++++ CH Sazonov et al., 1991a
Ferroceladonite * * KFe2+Fe3+Si4Oio(OH)2 +++ EMPA, XRD our data
Grossular* Ca3Al2[Si04l3 +++ EMPA, XRD Sazonov et al., 1991a; our data
Halloysite-TÀ1* Al2Si205(0H)4 I+++I EMPA, XRD Kabanov, 2001; our data
Hannotome** Ba2Al4Si12032 12H20 ++ EMPA our data
Hemimorpliite * * Zn,[Si207](0H)2H20 (++) EMPA, XRD
Hingganite-(Y)** Y2DBe2[Si04]2(0H)2 + EMPA
Hingganite -(Nd) * * * Nd2DBe2rSi04l2(0H)2 + EMPA
Joliannsenite** CaMnSi206 + EMPA
Kaolinite* Al,Si,05(0H)4 Ï++++1 EMPA, XRD, IR Sazonov et al., 1991a; our data
Laumontite* CaAl2Si4012-4H20 +++ EMPA, XRD
Magnesio-ferri-hornblende □ Ca,(Mg4Fe3+)Si7A10^(0H), ++ CH Sazonov et al., 1991a
Microcline KAlSi3Os +++ CM XRF, EMPA, XRD Sazonov et al., 1991a
Montmorillonite (Na,Ca)03(Al,Mg)2Si4Oi0(OH)2nH2O I+++I EMPA, XRD
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KA12(SÍ3A1)Oiq(OH)2_
Na03Fe3+2(Si.Al),01o(QH)2nH20
++++ (+++)
EMPA, XRD EMPA, XRD, IR
Sazonov et al., 1991a; Murzin et al., 2011; our data our data
Orthoclase*
KAlSi,Os
+++
CM, XRF, XRD, EMPA
Sazonov et al., 1991a; our data
Pargasite*
NaCa2(Mg4Al)Si6Al2Q22(OH)2
+++
EMPA, XRD
Pigeonite*
(Mg.Fe,Ca)2Si206
+++
EMPA, XRD
our data
Prelinite1
Ca2Al2SÍ3O10(OH)2
++++
EMPA
Sazonov et al., 1991a; our data
Pumpelly ite-(Mg) * * Talc*
Ca2MgAl2[Si207] [Si04](0H)2-ILO
Mg3Si4O10(OH)2_
++
+++
EMPA EMPA, XRD
our data
Murzin, Varlamov, 2010; our data
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Thorite*
Th[Si04
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Titanite*
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EMPA, O
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Tremo lite*
□ Ca2MfoSis022(0H)2
++
EMPA, XRD, O
Sazonov et al., 1991a; our data
(Ca,Na)i9(AI,Mg,Fe)i3|Si04Jio [Si,07]4(0HFm,n_
Vesuvianite**
+++
EMPA
our data
Wollastonite
CaSi03
++++
EMPA, XRD, O
Sazonov et al., 1991a
Zircon*
Zr[Si04
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EMPA
Murzin et al., 2010; our data
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Note. Occurrence of minerals: +++++ - rock-forming, major gangue and ore, ++++ - abundant, +++ - subordinate, ++ - rare, + - extremely rare (single findings). In third column, supergene minerals are given in round brackets and hypogene and supergene minerals are given in square brackets. The analytical methods of identification of minerals: EMPA - electron microprobe analysis, CM - chemical analysis; XRF - X-ray fluorescence; LA ICP MS - laser ablation inductively coupled plasma mass spectrometry; XRD - X-ray diffraction (single-crystal or powder method); O - optical data; H - micro-indentation hardness; IR - infrared spectroscopy; RS - Raman spectroscopy. CH - mineral is determined by chemistry (method is not specified; only for literature data). Minerals: * - minerals studied by the authors;
** - minerals identified by the authors for the first time at the Vorontsovskoe deposit; *** - minerals identified by the authors for the first time in Russian Federation;
**** - new mineral species found by the authors. New mineral species discovered at the Vorontsovskoe deposit are typed in bold. 1 - mineral is mentioned in literature without analytical data and reliable analytical data are published for the first time in this paper; ? - mineral is identified on the basis of chemical composition, however, this identification is doubtful. Formula ofboscardinite is given according to (Biagioni, Moelo, 2017), because it clearer reflects its isostructural correlation with ecrinsite rather than IMA formula. The following minerals are not included in Table but they are mentioned in literature without analytical data and any identification features: actinolite, ankerite, apophyllite, hedenbergite, datolite, marcasite, pyrargyrite, stilbite (desmine), thaumasite (Sazonov et al., 1991a); altaite, hessite, digenite, calaverite, tellurobismuthite, jarosite (Kabanov, 2001); aikinite, lead, freibergite (Vikentyev et al., 2016); wittichenite (Vikent'eva, Vikentev, 2016), gruzdevite, polhemusite, silvialite (Stepanov et al., 2017); aurostibite, berthierite, bismuth, dyscrasite, jentschite, cobaltite, russellite (Vikentyev et al., 2019).
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The Vorontsovsko-Peschanskaya ore-magmatic system is situated in the southwestern contact of the Auerbakh pluton (Minina, 1994). The Vorontsovskoe deposit is located in the southern part of the system, at some distance from the contact with intrusive rocks of the Auerbakh pluton (Fig. lc). The host volcano-sedimentary rocks of the deposit form a monocline that gently dips to the west and plunges to the north. The basement of this structure represents a limestone sequence about 1 km thick, often recrystallized to marbles, with interlayers of tuffites and siltstones. Limestones are overlain by volcanosedimentary and volcanic rocks: tuff siltstones, tuffites, porphyry diorites, and tuffs. Abundant coarse-clastic breccias with tuff matrix occur at the contact of volcanosedimentary and volcanic rocks with limestones (Korzhinsky, 1948).
The boundaries of the Vorontsovskoe deposit are mainly tectonic with a longitudinal Vorontsovsky fault dipping to the west at an angle of 70-80° in the west and a NW-trending South Peschansky fault in the southwest. The ore bodies are exposed at the surface and eroded in the east and pinch out along the dip and strike in the north (Vikentyev et al., 2016).
The northern open pit of the deposit exposes a wedge-shaped body of volcanosedimentary rocks with dominant tuffs of intermediate composition and tuf-faceous sandstones (Fig. 3a). The western part of this body is bounded by a large fault (Fig. 3b). The main volume of ore-bearing breccias is localized in the foot-wall contact of the body of volcanosedimentary rocks and limestones. Both limestones and volcanosedimentary rocks are brecciated. The breccias consist of semi-rounded and angular limestone fragments up to 25 cm in size in a clay-carbonate and volcanosedimentary matrix (Vikentyev et al., 2016).
Various metasomatic rocks formed over a long period are abundant at the deposit. The earliest skarns are associated with intrusive bodies of the Auerbakh pluton. The thickness of the skarn zones is typically 10-20 m and their length reaches 1.5 km and more. Skarns are replaced by propylites at some distance from intrusive bodies. The propylites replace all volcanosedimentary rocks and compose an outer zone of skarns. Beresites and listvenites are developed after gabbro, mafic to intermediate volcanic rocks, dolerite dikes, and tuffites. The thickness of zones of the beresite-listvenite rocks does not exceed few meters and their length reaches 40-60 m. Abundant quartz-sericite metasomatites are younger than beresites and listvenites and also host a large volume of gold mineralization. Jasperoids occur at the contacts of mafic to intermediate dikes with
limestones, as well as in limestones. In the upper horizons of the deposit, rocks affected by clay alteration host low-temperature gold mineralization (Sazonov et al., 1998; Vikentyev et al., 2016). Supergene rocks are also widespread at the Vorontsovskoe deposit. A weathering mantle up to 60 m thick is developed after volcanosedimentary and intrusive rocks of the Auerbakh complex, whereas carbonate rocks are subject to the formation of karst, which is composed of products of displaced weathering mantle up to 120 m thick (Vikentyev etal., 2016).
The ore body with economic Au content at the deposit has a torch-like shape (Cheremisin, Zlotnik-Khotkevich, 1997). Gold mineralization is mainly hosted by breccias and also altered volcanosedimen-tary rocks. Two main brecciation stages are distinguished at the deposit, which resulted in the formation of (i) large-block breccias with fine-crystalline ore matrix and dominant pyrite after marbles and (ii) breccias with branchy contours and realgar-orpiment matrix in the first stage breccias (Stepanov et al., 2017). The second stage breccias are matrix- and clast-supported in the central and marginal parts of the breccia bodies, respectively.
It was previously concluded that the Vorontsovskoe gold deposit belongs to the Carlin-type (Sazonov et al., 1998; Vikentyev et al., 2016; Murzin et al., 2017). This conclusion is based on a combination of structural and compositional features of gold mineralization including the abundant ore-bearing breccias and Tl minerals, some of which are associated with native gold similarly to the Carlin-type gold deposits (Dickson et al., 1979; Radtke, 1985; Volkov, Sidorov, 2016). Another viewpoint on the genesis of the Vorontsov-skoe deposit suggests that, according to a number of features (e.g., origin of breccias, geodynamic setting of the deposit, etc.), some ores (first of all, gold-bearing breccias) can be considered epithermal, which formed in the marginal part of the ore-magmatic system associated with igneous rocks of the Auerbakh complex (Stepanov et al., 2019). The specific features of geological structure of the ore body is composed of breccias; the morphology of limestone fragments, volcano-sedimentary rocks and metasomatites, the structures, textures, and mineral composition of breccia matrix indicate afluid-explosive nature ofbreccias (Stepanov et al., 2017). The formation of ore breccias could occur due to fluid decompression in near-surface conditions, which is typical of epithermal deposits (White, Heden-quist, 1995). A spatial combination of a large amount of rocks with various geochemical features in breccias
Fig. 3. Cross-sections of the Vorontsovskoe deposit:
a - geological cross-section, modified after (Cheremisin, Zlotnik-Khotkevich, 1977; Sazonov et al., 1998).
1 - Neogene-Quaternary deposits; 2 - Devonian karst; 3 - limestone; 4 - tuff siltstone, tuff sandstone, tuff conglomerate; 5 - andesite, andesitic tuff and lava breccias; 6 - 1st stage breccias; 7 - lamprophyre dikes; 8 - diorite-porphyrite dikes; 9-11 -metasomatites: 9 - quartz-sericite, 10-quartz-sericite-albite, 11 -berezite-listveniteandchlorite-sericite; 12 - ore shoots with ordinary Au grades; 13 - gold-rich ore shoots; 14 - breccias with realgar-orpiment matrix.
b - photo of the Northern open pit with Vorontsovsky reverse fault (red dotted line).
combined with hydrothermal-metasomatic processes, which accompanied the formation of breccia matrix, resulted in the formation of several unique (including new) minerals, which exhibit contrasting geochemi-cal associations. Gladkovskyite MnTlAs3S6 (Kasatkin et al., 2019) is a typical example; Mn was probably sourced from Mn-rich carbonate sedimentary rocks, whereas Tl, As, and S could derive from hydrothermal fluids generated by a magmatic source. Thus, the ge-
netic type of the Vorontsovskoe deposit remains a matter of debate.
Ore types and mineral assemblages of the Vorontsovskoe deposit
Several types of ores are identified at the Vorontsovskoe deposit. They are associated with various volcanosedimentary and hydrothermal-metasomatic
rocks: e.g., primary ores in limestones and volcano-sedimentary rocks and oxidized ores (Vikentyev et al., 2016). The primary ores include: 1) disseminated gold-magnetite-sulfide ores in calcareous skarns; 2) disseminated gold-polymetallic ores in jasperoids; 3) finely disseminated gold-pyrite-arsenopyrite ores in tuff sandstones and tuff siltstones; 4) finely disseminated goldpyrite-realgar ores in carbonate breccias, and 5) gold-sulfide-clay ores in argillic rocks. The oxidation zone contains gold-oxihydroxide-clay ores.
Our studies on samples collected at the deposit in 2013-2020 show that the ore breccias after carbonate rocks exhibit the greatest variety of minerals, including all new minerals (sulfarsenites and sulfantimonites with species-defining Tl, Hg, Pb, and Mn) and a number of rare sulfides and sulfosalts, many of which are found for the first time at the territory of the Russian Federation. The names of most mineral assemblages (see below) reflect the findings of these new minerals. Some of them (vorontsovite, gungerite, gladkovskyite, luborzakite, tsygankoite) are new minerals discovered at the deposit, whereas other minerals (boscardinite, parapierrotite, ecrinsite) are abundant in these mineral assemblages.
Carbonate breccias are typically composed of fragments of coarse- to medium-grained marblized limestones enclosed in ore matrix. Both marblized limestones and breccias underwent metasomatic alterations, which resulted in the formation of ore minerals. The main gangue minerals of the matrix include calcite and dolomite, which are accompanied by quartz, baryte, prehnite, clinochlore, and muscovite. The finegrained pyrite and realgar are major minerals of ore matrix and some assemblages can also contain major stibnite, arsenopyrite, orpiment ornative arsenic.
The deposition of high-temperature gangue minerals was followed by the formation of a medium-temperature sulfide-polymetallic assemblage (sphalerite, galena, chalcopyrite, alabandite, fahlores, native gold). It is most likely that the mineral assemblage with sulfarsenites and sulfantimonites formed at the last lowest-temperature stage of the hydrothermal process. Although As and Sb sources for sulfosalts are obvious, the source for S has not unambiguously been identified, yet.
A complex character of hydrothermal-metasomat-ic processes with successive telescoping of ore mineral assemblages developed in various volcanosedimen-tary and carbonate rocks was partly responsible for the presence of a large number of minerals with a unique chemical composition. For example, the formation of
ore breccias and accompanying metasomatic processes in marblized limestones, which are composed of Mn-rich calcite, led to the formation of an endemic sulf-arsenite assemblage of Mn- and Tl-bearing minerals. At the last stages of the ore-forming process, the early high- and medium-temperature minerals were replaced by polymetallic ore assemblage (galena, sphalerite, chalcopyrite, etc.) with rare sulfarsenites.
We identified nine most stable ore mineral assemblages, of which seven are found in carbonate breccias and two belong to magnetite skarns and oxidation zone, respectively. Each assemblage is confined to a specific ore type and is characterized by indicative features and unique minerals in comparison with other assemblages. Forthe sake ofbrevity, each assemblage is numbered from lto9 (Table 2).
The boscardinite-ecrmsite assemblage (no. 1) is recognized in carbonate breccias sampled at the lower horizons of the northern open pit (59°39'12" N, 60°12'53" E). It contains the widest spectrum of ore minerals with very rare Tl sulfosalts including most abundant isostructural boscardinite and ecrinsite, which form a solid solution series. Only this assemblage contains O-free minerals such as arsiccioite, getchellite, manganoquadratite, molybdenite, oyonite, pokhodyashinite, native silver, sinnerite, sicherite, stal-derite, «tennantite-(Mn)» (a potentially new mineral), weissbergite, as well as oxysalts and oxides (chromite, magnesiochromite, pumpellyite-(Mg), scheelite, sva-bite, thorite, zircon).
The vorontsovite-gungerite assemblage (no. 2). The samples with this mineral assemblage were collected at the ore stockpile of the deposit and off-balance ore stockpile no. 2. It is named after widespread new minerals vorontsovite, ferrovorontsovite (Kasatkin et al., 2018a), and gungerite (Kasatkin et al., 2022a). The assemblage is characterized by a broad isomorphism between various sulfosalts. Vorontsovite and ferrovo-rontsovite form a continuous solid solution series with a substitution of Hg for Fe. The As ^ Sb substitution is determined in gungerite and minerals of the cha-bourneite group. Vorontsovite, ferrovorontsovite and galkhaite also exhibit Tl ^ Cs isomorphism and cinnabar is characterized by S ^ Se isomorphic substitution. Both types of isomorphism are rather atypical at the deposit. Only this assemblage contains enneasar-torite, ferrovorontsovite, galkhaite, greigite, gungerite, heptasartorite and pararealgar.
The gladkovskyite (sulfarsenite) assemblage (no. 3). It is typical of the carbonate breccias, which were collected at the lowest horizons of the northern open pit,
Mineral assemblages in ores of the Vorontsovskoe deposit
Table 2
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Minerals
Assemblage Ore types Characteristic features Rock-forming, major Abundant Subordinate Rare
gangue and major ore
1. Boscardinite- Pyrite-realgar Largest amount of rare T1 sulfosalts Pyrite Aktashite Chalcopyrite Acanthite
écrinsite Realgar Arsenopyrite Christite Alabandite
Baryte Boscardinite Cinnabar Andorite
Abundant boscardinite and ecrinsite Calcite Chabournéite Coloradoite Arsiccioite
Clinochlore Ecrinsite Dalnegroite Bernardite
fonning solid solution series Dolomite Native gold Getchellite Dewitite
Muscovite Orpiment Metacinnabar Drechslerite
Late propylitization with rock- Prehnite Parapierrotite Wakabayashilite Galena
forming prehnite and abundant Quartz Routhierite Weissbergite Guettardite
annenite Sphalerite Zinkenite Hutchinsonite
Stibnite Diopside Imholite
Annenite Fluorapatite Manganoquadratite
Magnetite Native arsenic
Scheelite Native silver
Nowackiite
Oyonite
Philrothite
Pokhodyashinite
Rebulite
Sicherite
Sinnerite
Stalderite
«Tennantite-(Mn)»
Tennantite-(Zn)
Twinnite
Vorontsovite
Vrbaite
UK phase I
UK phase II
Albite
Andradite
Augite
Chromite
Hannotome
Magnesiocliromite
Ba-bearing orthoclase
Pumpellyite-(Mg)
Rutile
Svabite
Thorite
Titanite
Zircon
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2. Vorontsovite-gungerite Pyrite-realgar-stibnite Numerous minerals of extended solid solutions series (vorontsovite-ferrovorontsovite, dalnegroite-chabournéite) Pyrite Realgar Stibnite Calcite Clinochlore Dolomite Cinnabar (including Se- bearing) Dalnegroite Ferrovorontsovite Gungerite Parapierrotite Routhierite Sphalerite Vorontsovite Quartz Chabournéite Coloradoite Orpiment Baryte Bernardite Boscardinite Ecrinsite Enneasartorite Galkhaite Greigite Guettardite Heptasartorite Hutchinsonite Metacinnabar Native arsenic Native gold Pararealgar Wakabayashilite UK phase I UK phase II Goethite Rutile
Assemblage with Cs-bearing (galkhaite, vorontsovite, ferrovorontsovite) and Se-bearing (cinnabar) minerals
3. Gladkovskyite (sulfarsenite) Orpiment-pyrite-realgar As-bearing stibnite-free ores Orpiment Pyrite Realgar Baryte Calcite Alabandite Gladkovskyite Native gold Routhierite Vrbaite Clinochlore Dolomite Fluorapatite Auerbakhite Sphalerite Bernardite Christite Cinnabar Coloradoite Dalnegroite Gillulyite Hutchinsonite Imhofite Lorândite Philrothite Picotpaulite Rebulite Quartz Talc
Strongly dominant As over Sb in chemical composition of sulfosalts
Presence of sulfarsenites with species-defining Mn (gladkovskyite, auerbakhite)
4. Cinnabar- coloradoite- parapierrotite Pyrite-realgar-stibnite Assemblage with macroscopic cinnabar aggregates Pyrite Realgar Stibnite Calcite Dolomite Cinnabar Coloradoite Orpiment Parapierrotite Sphalerite Baryte Clinochlore Quartz Prehnite Aktashite Metacinnabar Native arsenic Routhierite Zinkenite Acanthite Andorite Arsenopyrite Bernardite Chabournéite Christite Galena Gersdorfite Guettardite Laffittite Native gold Nowackiite
Abundant parapierrotite with crystals up to 1 mm in size
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Minerals
Assemblage Ore types Cliaracteristic features Rock-forming, major gangue and major ore Abundant Subordinate Rare
Abundant coloradoite with very large grains up to 0.12 x 0.06 mm in size Picotpaulite Roshchinite Tennantite-(Zn) Bismoclite Diopside Ferberite Fluorapatite Microcline Muscovite Rutile
5. Luborzäkite-clerite Pyrite-realgar Enrichment of ore system in Mn (Mn-bearing calcite, dolomite, sphalerite and sulfosalts) Pyrite Realgar Baryte Calcite Alabandite Sphalerite Clinochlore Diopside Aktashite Boscardinite Clerite Luborzâkite Arsenopyrite Chabournéite Coloradoite Ecrinsite
Presence of Tl-free sulfarsenites and sulfantimonites with species-defining Mn (luborzâkite, clerite) Dolomite Routhierite Guettardite Native gold Orpiment Parapierrotite Stibnite Tennantite-(Zn) Twinnite UK phase II
Iisomorpliic As-Sb substitution in luborzâkite, clerite, boscardinite, parapierrotite, chabournéite, and écrinsite Chernovite-(Y) Fluorapatite Muscovite Prehnite
Absence of quartz
6. Assemblage with native Native arsenic-arsenopyrite-realgar Presence of abundant native arsenic Arsenopyrite Native arsenic Native gold Orpiment Tetrahedrite-(Zn) Diopside Aktashite Benavidesite
arsenic Inclusions of euhedral arsenopyrite crystals up to 1 mm in native arsenic Realgar Arsenolite Claudetite Calcite Pyrite Baryte Clinochlore Muscovite Fluorapatite Vesuvianite Chalcopyrite Cubanite Galena Hessite
Most abundant and largest inclusions of native gold Dolomite Quartz Jamesonite Parapierrotite Ramdohrite
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Absence of Tl- and Hg-bearing minerals except for rare aktasliite and parapierrotite Presence of vesuvianite Sphalerite Stibnite Tennantite-(Fe) Tennantite-(Zn) Tetrahedrite-(Fe) Rutile Titanite
7. Assemblage with tsygankoite Arsenopyrite-pyrite-realgar Presence of major arsenopyrite Enricliment of ore system in Mn (the presence of alabandite and Mn-bearing calcite, dolomite, sphalerite) Presence of sulfantimonites with species-defining Mn (tsygankoite, benavidesite) Presence of zoned fluorapatite crystals with isomorphic P and As, F, CI and OH up to the formation of chlorapatite and turneaureite Arsenopyrite Pyrite Realgar Calcite Clinochlore Dolomite Alabandite Orpiment Sphalerite Tsygankoite Fluorapatite Tilasite Aktashite Duranusite Native arsenic Native gold Routhierite Titanite Benavidesite Coloradoite Dalnegroite Guettardite Jordanite Veenite Baryte Chlorapatite Gasparite-(La) Geikielite Hydroxy lapatite Pyrophanite Turneaureite
8. Assemblage with Bi minerais Magnetite-sulfide Presence of Bi minerals Association with skarns Large arsenopyrite inclusions in massive magnetite Numerous inclusions of sulfides and Bi tellurides in magnetite Magnetite Andradite Calcite Arsenopyrite Chalcopyrite Pyrite Epidote Native gold Pyrrhotite Sphalerite Quartz Bismuthinite Galena Native gold Ikunolite Joseite-A Lillianite Pavonite Tetradymite
9. Supergene assemblage Native gold-oxihydroxidc-clay Abundant Fe and Mn oxides and hydroxides and clay minerals including smectites Presence of various sulfates Kaolinite Goethite MontmoriUonite Quartz Pyrite Calcite Dolomite Gypsum Halloysite Hematite Arsenopyrite Chalcopyrite Galena Native gold Sphalerite Baryte Cerussite Coronadite Crvptomelane Dickite Fluorapatite Malachite Bornite Covellite Djurleite Hawleyite Tennantite-(Zn) Akhtenskite Anglesite Asbolan Azurite Bayldonite Beaverite-(Cu) Birnessite
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Minerals Rare Bixbyite Brochantite Cesàrolite Chalcanthite Epsomite Hemimorphite Hollandite Kutnohorite Lithiophorite Manganite Manjiroite Pentahydrite Ramsdellite Ranciéite Rutile Starkeyite
Subordinate Nontronite Pyrolusite Rhodochrosite Romanèchite Todorokite Vernadite
Abundant
Rock-forming, major gangue and major ore
Characteristic features
Ore types
Assemblage
approximately 50 m from its eastern wall (Fig. 4). The assemblage is named after gladkovskyite, a new Mn-Tl-sulfosalt (Kasatkin et al., 2019). This assemblage can alternatively be named sulfarsenite assemblage due to its unique As predominance over Sb, the complete absence of stibnite (as well as sulfantimonites), and general depletion in Sb. Auerbakhite, gillulyite, gladkovskyite, and lorandite occur only in this assemblage.
The cinnabar-coloradoite-parapierrotite assemblage (no. 4). Cinnabar, coloradoite, and parapierro-tite are rare minerals of the Vorontsovskoe deposit, but they are abundant in assemblage no. 4 and occur either together or in pairs in each studied sample. The carbonate breccias with this assemblage were sampled in the northern open pit. Similarly to the vorontsovite-gungerite assemblage, this one is confined to pyrite-realgar-stibnite ores, but their indicative features and a list of minerals significantly differ. Cinnabar was previously identified as a very rare ore mineral (Sazonov et al., 1991a; Vikentyev et al., 2016), however, in our samples, it forms large macroscopic aggregates. Galois radoite and parapierrotite, which occur almost in all •ja ore assemblages confined to the carbonate breccias as ^ rare grains up to 50 pm, are found in this assemblage
in
^ as large crystals: up to 0.12 and 1 mm long, respective-^ ly. The quality of the parapierrotite crystals from this assemblage allowed us to solve for the first time the g structure of this sulfosalt (Plasil et al., 2018). Only this assemblage contains gersdorffite, laffittite, roshchinite,
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The luborzakite-clerite assemblage (no. 5). It is g typical of explosive breccias that contain the fragments H of metasomatically altered sedimentary (limestones « and marblized limestones) and volcanosedimentary § (tuff siltstones and sandstones) rocks and are stored g at off-balance ores dump no. 1. Samples of this dump ^ originate from the middle part of a tubular ore brec-« cia body at the contact of a volcanosedimentary wedge & and host carbonate rocks. Similar to the boscardinite-& ecrinsite assemblage, such assemblage is confined to ^ pyrite-realgar ore type with rare arsenopyrite, orpi-H ment, and stibnite. An interesting feature of this asia semblage is the enrichment of the ore-forming system i in Mn, which is most likely sourced from sedimentary and volcanosedimentary rocks. In addition to higher O Mn content in Mn-rich calcite and dolomite and abundance of alabandite and Mn-bearing sphalerite, Mn is < often detected in minor amount in accessory sulfosalts (aktashite, boscardinite, chabourneite, ecrinsite) in
Fig. 4. Gladkovskyite assemblage in situ of the Vorontsovskoe deposit:
a - sampling at the bottom of northern open pit; b - carbonate breccias with gladkovskyite assemblage. Photo: R.S. Palamarchuk.
contrast to other assemblages. Manganese in this assemblage is also included in the composition of sul-fosalts without species-defining T1 (luborzakite and clerite). This assemblage also contains chernovite-(Y).
The assemblage with native arsenic (no. 6). The breccias with this assemblage were collected at the dumps of the northern open pit. The main features of this assemblage are the presence of large (up to 34 cm) anhedral aggregates, isometric grains and nodules of native arsenic, which intergrows with gangue minerals of breccia matrix (calcite, dolomite, quartz, baryte, clinochlore, muscovite). It is most likely that native arsenic formed during the last low-temperature stage of the hydrothermal process due to the decomposition of the earlier realgar and orpiment. Native arsenic is partly oxidized and replaced by supergene films and crusts, which are composed of two As3+ oxides: arsenolite and claudetite. They often form the most part of the studied samples because of fast oxidation of native arsenic (Fig. 5). Native arsenic, arsenolite, and claudetite replace arsenopyrite and realgar and contain numerous largest (up to 0.1 mm) inclusions of native gold. Only this assemblage hosts cubanite, hessite, jamesonite, ramdohrite, tetrahedrite-(Fe), tetrahedrite-(Zn), tennantite-(Fe), and vesuvianite.
The assemblage with tsygankoite (no. 7). This was sampled at the main ore stockpile of the deposit. The assemblage is named after tsygankoite, a new mineral with a unique combination of species-defining elements (Kasatkin et al., 2018b). In addition to gladkovskyite and luborzakite-clerite assemblages, this one
also contains sulfosalts with species-defining Mn. All three assemblages contain rock-forming Mn-rich calcite and dolomite, alabandite and Mn-bearing sphalerite. A significant difference between the assemblages is related to the types of Mn-sulfosalts: sulfarsenites (gladkovskyite, auerbakhite) in assemblage no. 3, sul-fantimonites and sulfarsenites without species-defining T1 (luborzakite, clerite) in assemblage no. 5 and only sulfantimonites (tsygankoite, benavidesite) in assemblage no. 7. Only this assemblage includes duranusite, jordanite, tsygankoite, veenite, chlorapatite, gasparite-(La), geikielite, hydroxylapatite, pyrophanite, and turneaurite.
The assemblage with Bi minerals (no. 8). Only two Bi-bearing minerals (vikingite and bismoclite) are found in carbonate breccias. However, several rare Bi sulfides, sulfotellurides and Bi-bearing sulfosalts (bismuthinite, ikunolite, joseite-A, lillianite, pavonite, tetradymite) are identified in magnetite-calcite-andra-dite-epidote skarns collected at the southern flank of the deposit, in the dumps of the southern open pit.
The supergene assemblage (no. 9). The oxidation zone was exposed by the southern open pit at the contact of volcanosedimentary rocks with underlying limestones and is described in a number of publications (Sazonov et al., 1991a; Rindzunskaya et al., 1995a, b; Kabanov, 2001; Vikentyev et al., 2016). The oxidized ores have also been mined at the southern flank of the northern open pit. In the oxidation zone, more than 90 vol. % is comprised of clays (kaolinite, halloysite), smectites (beidellite, montmorillonite, nontronite), hy-
Fig. 5. Assemblage with native arsenic. A fragment of a large nodule of native arsenic with realgar and native gold (small white grains) inclusions, supergene arsenolite/ claudetite, and gangue minerals (black).
BSE image.
dromica, quartz, carbonates (calcite, dolomite), fluorapatite, feldspars, etc. The ore minerals (<10 vol. %) mainly include Fe and Mn oxides and hydroxides, native gold, and a small amount of sulfides with dominant pyrite (Kabanov, 2001). The supergene Fe minerals include only goethite and hematite, whereas rare Mn oxides and hydroxides are more diverse, e.g., akhtenskite, birnessite, bixbyite, cesarolite, manjiroite, etc. (Figs. 6a, 6b; Table 2). This mineral assemblage also comprises supergene sulfides (covellite, djurleite, hawleyite), carbonates (azurite, cerussite, kutnohorite, malachite, rhodochrosite), and sulfates (anglesite, bea-verite-(Cu), brochantite, chalcanthite, gypsum, pen-tahydrite, starkeyite) (Fig. 6c).
Analytical methods
Mineral descriptions are based on the observations under a Zeiss Discovery V8 stereomicroscope. The optical properties of ore minerals in reflected light were studied under a MIN-8 polarizing microscope with an 01-12 opaque illuminator and a Leitz Wetzlar Type 307-107.002 in both the air and immersion using cedar oil (refractive index nd = 1.516). The reflectance spectra were registered using an UMSP-50 universal microspectrophotometer (Opton-Zeiss, Germany) in the air relative to a WTiC standard with a monochro-mator gap spectral width oflO nm.
The micromorphology and chemical composition of minerals were studied by scanning electron microscopy (SEM) and electron microprobe analysis (EMPA) using both energy and wavelength dispersive spectrometers (EDS and WDS, respectively). A preliminary study of polished sections and semi-quantitative chemical analysis of minerals were carried out in a laboratory of the Fersman Mineralogical Museum, Russian Academy of Sciences (FMM RAS, Moscow) on a CamScan 4D scanning electron microscope equipped with a Si(Li) energy-dispersive detector and an INCA Oxford microanalyzer at an accelerating voltage of 20 kV, a beam current of 5 nA on metallic cobalt, and a beam diameter of5pm.
Quantitative chemical composition was partly analyzed in the laboratory of the FMM RAS on a JCXA-733 Superprobe JEOL microprobe equipped with a Si(Li) energy-dispersive detector with an ATW-2 thin window and an INCA X-MAX (Oxford Instruments) analytical system at an accelerating voltage of
Fig. 6. Supergene assemblage in situ of the Vorontsovskoe deposit:
a - dumps of southern open pit with supergene mineralization; b - brown Fe oxy-hydroxides and black Mn oxy-hydroxides; c - white powdery sulfates. Photo: A.V. Kasatkin.
20 kV, a beam current of 2 nA and a beam diameter of 2 pm. The chemical composition of minerals was also determined by a Cameca SX 100 wavelength electron probe microanalyzer at the Joint Laboratory of Electron Microscopy and Microanalysis of the Department of Geological Sciences at the Masaryk University and Czech Geological Survey, Brno, Czech Republic. The analytical conditions were as follows: an accelerating voltage of 25 kV, a beam current of 2-20 nA, and a beam diameter of 1-2 pm for elements, sulfides, arsenides, tellurides and sulfosalts and an accelerating voltage of 15 kV, a beam current of 10 nA, and a beam diameter of 8 pm, for halides, oxides, and oxysalts. For all minerals, peak counting times (CT) were 10-20 s for major elements and 20-120 s for trace elements with a background CT 5-10 and 10-20 s, respectively.
The standards, analytical X-ray lines and analyzing crystals (in parentheses) were as follows:
- for oxygen-free compounds (except for halides): chalcopyrite, SKa line (PET); Mn, MnZTa (LIF); FeS2, FeKa (LLIF); Co, CoKa (LLIF); pararammelsbergite, Ni^a (LLIF) and AsZp (TAP); Cu, CuKa (LLIF); ZnS, ZnKa (LLIF); PbSe, SeZp (TAP) and PbMa (PET); Mo, MoZa (LPET); Ag, AgZa (PET); Cd, CdZp (PET); Sb, SbZp (PET); pollucite, CsZa (LPET); HgTe, TeZp (LPET) and HgMa (LPET); Tl(Br,I), TIMa (PET); Bi, BiMp (PET);
- for halides and oxysalts: topaz, FKa (PCI); al-bite, NaKa (TAP); pyrope, MgZTa (TAP); andalusite, AlZTa (TAP); wollastonite, SiZTa (TAP) and CaKa (LPET); fluorapatite, P^a (PET); SrS04, S^a (LPET) and SrZa (TAP); vanadinite, ClKa (PET), VKa (LLIF) and PbMa (LPET); orthoclase, KKa (PET); ScV04, ScKa (PET); Ti02, Ti^a (LPET); chromite, Cr^a (LPET); Mn2SiO4, Mn^a (LLIF); andradite, FeKa (LLIF); Co, Co^a (LLIF); Ni2SiO4, NiKa (LLIF); 1am-merite, CuKa (LLIF) and AsZa (TAP); gahnite, ZnKa (LLIF); YAG, YZa (TAP); zircon, ZrZa (TAP); co-lumbite, NbZa (LPET); baryte, BaZa (PET); LaP04, LaZa (PET); CeP04, CeZa (PET); PrP04, PrZp (LLIF); NdP04, NdZa (LLIF); SmP04, SmZa (LLIF); EuP04, EuZp (LLIF); GdP04, GdZp (LLIF); TbP04, TbZa (LLIF); DyP04, DyZa (LLIF); HoP04, HoZp (LLIF); ErP04, ErZa (1LLIF); TmP04, TmZa (LLIF); YbP04, YbZa (LLIF); LuP04, LuMp (TAP); CrTa2O6, TaZa (TAP); W, WZa (LLIF); Th02, ThMa (LPET); U02, UMP (LPET).
The raw intensities were converted to concentrations using X-PHI matrix-correction software (Merlet, 1994). Inter-REE interferences were solved by empirically determined correction factors.
Raman spectra were collected in the Laboratory of Raman spectroscopy of the Masaryk University on a Horiba LabRAM HR Evolution spectrometer equipped with an Olympus BX 41 optical microscope, a diffraction grating with 600 grooves per millimeter, a Peltier-cooled, Si-based charge-coupled device (CCD) detector and three (473,532, and 633 nm) lasers with a beam power at the sample surface of 5-10 mW. The Raman signal was collected in a range of 100-4000 cm-1; a beam diameter varied from 1 to 2.6 pm and a lateral resolution was 1 to 2 pm. The wavenumber was calibrated using the Rayleigh line and low-pressure Ne-discharge lamp emissions. The wavenumber accuracy was -0.5 cm-1 and the spectral resolution was ~2 cm-1. Band fitting was done after an appropriate background correction, assuming Voigt function, i.e., the convolution of the Lorentzian and Gaussian functions for the individual bands' shapes (PeakFit; Jandel Scientific Software).
Raman spectra of good quality were obtained for most transparent and translucent orange and red sulfo-salts (auerbakhite, gillulyite, gladkovskyite, gungerite, lorandite, rebulite, hutchinsonite). As for opaque (especially, black sulfides and sulfosalts), these minerals are characterized by high absorption coefficients of laser radiation and a small depth of its penetration into the analyzed sample. This leads to vigorous heating of a laser beam-exposed surface layer of the sample and its local destruction, although the scattered radiation compared to absorbed one is insignificant.
For XRD analysis, the mineral grains preliminary studied by EMPA and, in some cases, Raman spec-troscopy, were extracted from polished sections and analyzed in the laboratories of the Department of Geo-sciences of the University of Padova (Padova, Italy) and the Institute of Physics of the Academy of Sciences of Czech Republic (Prague, Czech Republic).
At the University of Padova, single-crystal (SXRD) and micro-powder X-ray (PXRD) data were collected using a Rigaku Oxford Diffraction SuperNova diffractometer equipped with a Pilatus 200K Dectris detector and an X-ray micro-source (MoZTa radiation) at an accelerating voltage of 50 kV, a beam current of 0.12 mA, and a beam size on sample of about 0.12 mm. The detector-to-sample standard distance was 68 mm. The total exposure time for single-crystal data varied from 15 min (determining unit-cell parameters for relatively large crystals) up to 90 h (registration of structural data on 10-15-pm-sized crystals). The powder patterns (up to dmin = 0.8 A) were recorded on the same device in a microdiffraction mode with
0-360°phirotationscanandanexposuretimevariedfrom 30 min to 12 h. The standard powder diffraction patterns were also obtained on a PANalytical 9-9 dif-fractometer using CoKa radiation at an accelerating voltage of 40 kV and a beam current of 40 mA in a stepwise mode (step 0.033° at 29) at the Department of Geosciences of the University ofPadova.
In the laboratory of the Institute of Physics of the Academy of Sciences of Czech Republic, the studies were carried out on a Rigaku Oxford Diffraction SuperNova single crystal diffractometer equipped with an Atlas S2 CCD detector, at a MoA"a radiation, an accelerating voltage of 50 kV, a beam current of 30 mA, and an X-ray beam focus size of 0.3 mm. The sample-to-detector distance was 55 mm for the standard single-crystal data and 120 mm for structural data during the long-time collection. The exposure time varied from 15 min (determination of unit-cells parameters for relatively large crystals) up to 14 days (registration of structural data for the most complex sulfosalts such as gungerite, tsygankoite, etc.). This device also has a Gandolfi mode, which allows collection of the PXRD data. The sample-to-detector distance in this mode was 53.5 mm and the standard exposure time was 25 min.
Description of minerals Elements
Native arsenic was first described by Sazonov et al. (1991a) as isometric crystals and anhedral grains up to 1 mm in size embedded in the matrix of ore breccias or as tiny inclusions up to 10-15 pm in stibnite. The mineral was identified by its optical properties, chemical composition, and XRD data. Native arsenic contains up to 0.1 wt. % Sb and S. In 2007, large native arsenic aggregates weighing more than 1 t were exposed in the northern open pit (Vikentyev et al., 2016). They are confined to metasomatically altered tuffaceous rocks in the upper part of the deposit. Metasomatite is mainly composed of quartz, which is crossed by brec-ciation zones up to 5 cm thick with numerous veinlets, lenses, and pockets of native arsenic aggregates up to 3 cm. Native arsenic and prismatic arsenopyrite also occur in rocks beyond the brecciated zones, where they form dense, uniformly dispersed inclusions up 0.5 mm across. Native arsenic contains numerous grains of native gold. According to EMPA, no trace elements were detected in native arsenic. The surface of native arsenic is rapidly oxidized in air and covered by arsenolite films. The mineral assemblage with native arsenic also
contains alabandite, sphalerite, fahlores, and Cl-bea-ring fluorapatite (Murzin et al., 2011).
Our samples with native arsenic-bearing assemblage no. 6 collected in the dumps of the northern open pit most likely derive from the material extracted in 2007. This suggestion is supported by extensive replacement of native arsenic by supergene minerals, which occurred in the dumps. Native arsenic occurs in breccias as veinlets up to 3 cm thick composed of brown to black lamellar aggregates, which are partly oxidized from the surface up to the formation of arse-nolite and claudetite, in assemblage with brightly red realgar and yellow orpiment (Figs. 7a-7d, 91). Native arsenic is a major ore mineral of the assemblage no. 6, where it is found as aggregates up to 3-4 cm in size, isometric grains and nodules intergrown with gangue minerals of the breccia matrix (calcite, dolomite, quartz, baryte, clinochlore, muscovite, etc.) and contains inclusions of realgar, arsenopyrite, pyrite, fahlores, and abundant native gold grains up to 0.1 mm in size. Native arsenic is a host to numerous inclusions of native gold, arsenopyrite, bournonite, and tennantite-(Fe). Native arsenic also rarely occurs in assemblage no. 4, where it forms inclusions up to 50 pm in stibnite and at the contact of the latter with calcite and dolomite (Fig. 8h). The mineral is observed together with various Pb-Cu-Ag-bearing sulfosalts (andorite, ten-nantite-(Zn), zinkenite), orpiment, realgar, coloradoite, and sphalerite. The parameters of the hexagonal unit cell of native arsenic calculated from powder diffraction pattern are provided in Table 3.
Native copper was observed in the oxidation products of sphalerite and chalcopyrite in garnet skarn (Vikentyev et al., 2016).
Native gold of the deposit is the main target of mining, therefore, it has been studied in details (Sazonov et al., 1991a; Murzin, Varlamov, 2010; Murzin et al., 2011; Vikentyev et al., 2016). In various assemblages, native gold forms small (e.g., <0.1 mm) rounded and angular particles or interstitial, lamellar, and globular grains. Some grains show crystal faces. Isometric crystals and rounded and elongated grains of native gold are abundant in quartz-mica-carbonate matrix and as inclusions in pyrite, arsenopyrite, native arsenic, Pb sulfosalts, and fahlores. The intergrowths of native gold with realgar are less common. According to Vikentyev et al. (2016), the Ag content of native gold varies from zero in orpiment-realgar ores of carbonate breccias and argillisites, where the fineness of gold reaches 989 and 993 %o, respectively, up to 37.8 wt. % in pyrite-pyrrhotite ores of skarn (the fine-
Fig. 7. Morphology of native arsenic of the Vorontsovskoe deposit:
a - monomineral brown segregation; b - black aggregates in assemblage with powdery coatings of white arsenolite/ claudetite, films of yellow orpiment and orange realgar; c - coarse-grained aggregate with a perfect cleavage; d - a nodule of native arsenic partly replaced by supergene arsenolite/claudetite in assemblage with native gold and relict arsenopyrite in a matrix composed of quartz, calcite and muscovite.
Collections of A.V Kasatkin (a, d), Museum «Shtufnoi Kabinet», Severouralsk (b, c). Photo: A.D. Kasatkina (a), M.V. Tsyganko (b, c), BSE image (d).
ness of gold is only 614 %o). Locally, native gold also contains Hg (up to 5.5 wt. %) and Cu (up to 0.7 wt. %).
In a sample from the main ore stockpile, we found a unique native gold cluster in calcite measuring 1.5 mm long (Fig. 9a). Native gold was also observed in all above mineral assemblages. It is most often found in assemblage no. 6 as grains up to 0.1 mm in size, which are disseminated in gangue minerals of breccias (carbonates, quartz, baryte, muscovite, etc.), native arsenic, arsenolite, and claudetite and at their contact with realgar and arsenopyrite (Figs. 5, 8d). In this assemblage, native gold contains Ag and Hg (average for ten grains, wt. %): 87.12 Au, 8.42 Hg, 5.01 Ag, total 100.55. The empirical formula based on the metal sum of one is Au083Ag009Hg0 08.
Native silver rarely occurs as fine dissemination in ores (Vikentyev et al., 2016). In our samples, the Au-bearing silver («kustelite») forms very rare rounded grains up to 20 pm in diameter in orpiment from assemblage no. 1. The chemical composition of native silver is (wt. %): 71.68 Ag, 28.15 Au, total 99.83; it corresponds to the empirical formula based on the metal sum of one Ag082Au018.
Sulfides, arsenides, tellurides
Acanthite Ag2S is very rare. It occurs in assemblages nos. 1 and 4 as single rounded grains up to 10 pm in size embedded in calcite. The chemical composition of the mineral is close to the stoichiometric Ag2S (Table 4).
Alabandite MnS was first recorded by Sazonov et al. (1991a) in one sample as crystals or anhedral grains up to 0.05-0.1 mm across disseminated in carbonate and, locally, intergrown with pyrite. The mineral was identified optically and by chemical composition (up to 3.5 wt. % Fe, up to 0.1 wt. % Cd and Hg). Murzin and Varlamov (2010) described stoichiometric alabandite, which forms aggregates up to0.15 mm in gangue minerals of breccias in assemblage with greigite, as well as individual crystals and intergrowths with Mn-bearing sulfosalts in realgar. Murzin et al. (2011) also reported on numerous rounded alabandite grains up to 50-70 pm across in native arsenic and arsenopyrite. This alabandite contains Fe (0.6 wt. %) and Zn (0.1wt.%).
In our samples, alabandite was found in mineral
assemblages nos. 1,3,5, and 7. In assemblage no. l,it is rare in comparison with assemblages nos. 3, 5, and 7.
Fig. 8. Sulfides, tellurides and sulfosalts in carbonate breccias of the Vorontsovskoe deposit:
a - crystalline alabandite with inclusions of small tsygankoite crystals and realgar rim in dolomite and calcite; b -coloradoite in assemblage with sphalerite, stibnite, and routhierite in calcite; c - coloradoite grains at the contact with stibnite and orpiment; d - prismatic duranusite crystal rimmed by tilasite in dolomite and calcite with alabandite; e - prismatic jalpaite crystal in chalcopyrite; f - Zn-Mn-bearing metacinnabar around the Hg-Mn-bearing sphalerite grain in a matrix composed of dolomite, calcite, and quartz with cinnabar; g - picotpaulite grain in calcite and clinochlore with a small pyrite crystal; h - stibnite with inclusions of tennantite-(Zn) and native arsenic in calcite; i - rounded tetradymite grain at the contact with magnetite and calcite.
BSE images.
Alabandite typically forms cubic crystals or subhedral grains up to 0.2 mm in size dispersed in gangue minerals of breccias (Figs. 8a, d). Alabandite was a source of Mn for late-stage low-temperature sulfosalts. The relics of alabandite are found in Mn-bearing sulfarse-nites and sulfantimonites (gladkovskyite, luborzakite, tsygankoite), which replace it partly or completely (Figs. 17i, 26g). Small inclusions of Mn-bearing sulfosalts in alabandite crystals are observed as well (Fig. 8a). The mineral has black color and submetallic luster. In reflected light, it is grayish white but looks light gray at the contact with tsygankoite, which has higher reflectance. The chemical composition of alabandite is stoichiometric (Table 4). The parameter of the cubic unit cell is provided in Table 3.
Arsenopyrite FeAsS together with pyrite is one of the major ore minerals of altered volcanosedimen-tary rocks: the contents of both sulfides reach 2030 vol. %. Arsenopyrite forms metacrystals 0.05 to 23 mm in size and also replaces shell walls of mollusks or rock-forming minerals. In breccias, arsenopyrite occurs as acicular crystals up to 0.2 mm long and often intergrows with pyrrhotite. It rarely contains Ni (up to 0.2 wt. %) and Co (up to 0.1 wt. %). Arsenopyrite is also reported from wollastonite metasomatites (Sazo-nov etal., 1991a).
Arsenopyrite occurs in most mineral assemblages of our samples. In assemblages nos. 6 and 7, it is one of the major ore minerals. In assemblage no. 6, arsenopyrite occurs as euhedral crystals up to 1 mm included
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Unit-cell parameters of minerals from the Vorontsovskoe deposit (our data)
Table 3
Nn AiltlPl^ll tlllTIA Crystal Unit cell parameters Me-
1NO. V111ILI111 1111111L As. no. system a, A b, A c,Ä a, ° K A3 thod
Elements
1 Arsenic 6 Trig. 3.7395(2) 10.5246(8) 127.46(2) P
Sulfides, arsenides, tellurides
2 Alabandite 1 Cub. 5.200(1) 140.61(7) SC
3 Arsenopyrite 8 Mon. 5.739(5) 5.690(5) 5.775(4) 112.05(8) 174.8(2) SC
4 Chalcopyrite 1 Tetr. 5.300(3) 10.439(9) 293.2(3) SC
5 Cinnabar 1 Trig. 4.1590(5) 9.212(2) 138.00(4) P
6 Cinnabar 4 Trig. 4.1473(3) 9.467(1) 141.01(2) P
7 Coloradoite 4 Cub. 6.435(11) 266.5(8) SC
8 Covellite 9 Hex. 3.7863(2) 16.352(2) 203.01(2) P
9 Djurleite 9 Mon. 26.908(6) 15.722(2) 13.513(2) 90.42(2) 5716(1) P
10 Galena 9 Cub. 5.9522(10) 211.12(8) SC
11 Getchellite 1 Mon. 11.910(4) 9.0389(13) 10.168 (9) 116.23(7) 981.9(9) SC
12 Greigite 2 Cub. 9.8894(8) 967.20(22) P
13 Hawleyite 9 Cub. 5.8060(6) 195.71(6) SC
14 Lôllingite - Orth. 5.2846(9) 5.9669(8) 2.8736(7) 90.61(2) P
15 Metacinnabar 4 Cub. 5.7295(3) 188.08(3) P
16 Orpiment 3 Mon. 11.475(1) 9.528(1) 4.248(1) 90.52(1) 464.52(7) P
17 Pararealgar 2 Mon. 9.968(3) 9.690(5) 8.574(8) 97.11(5) 821.9(9) SC
18 Pyrite 1 Cub. 5.4145(4) 158.74(4) SC
19 Pyrite 9 Cub. 5.408(13) 158.2(6) SC
20 Realgar 1 Mon. 9.325(1) 13.562(2) 6.586(1) 106.43(2) 798.9(2) P
21 Sphalerite 1 Cub. 5.4047(4) 157.88(3) P
22 Stibnite 4 Orth. 11.280(2) 11.276(2) 3.833(1) 487.5(1) SC
23 Wakabay a shilite 1 Orth. 25.21(3) 14.62(3) 6.65(4) 2450(16) SC
24 Wakabay a shilite 2 Orth. 25.40(3) 14.558(10) 6.432(5) 2378(4) SC
Sulfosalts
25 Aktashite 5 Trig. 13.639(4) 9.303(7) 1499(1) SC
26 Auerbakhite 3 Orth. 15.3280(15) 7.662(7) 16.6330(14) 1953.40(18) SC
27 Bernardite 3 Mon. 15.72(2) 8.18(2) 10.76(4) 91.54(6) 1383.1(2) SC
28 Boscardinite 1 Tricl. 8.080(1) 8.730(2) 22.474(4) 90.78(1) 97.08(1) 90.93(1) 1572.8(3) P
29 Boulangerite - Mon. 21.592(6) 23.489(15) 8.0758(13) 100.640(19) 4025(3) SC
30 Bournonite - Orth. 8.173(4) 8.704(4) 7.795(10) 554.5(8) SC
31 Chabournéite 1 Tricl. 16.327(7) 42.677(17) 8.559(9) 95.75(5) 89.11(6) 96.79(3) 5892(7) SC
32 Christite 3 Mon. 6.11(5) 16.2(2) 6.11(4) 96.7(6) 600(10) SC
33 Clerite 5 Orth. 11.4021(12) 14.3790(15) 3.7908(4) 621.50(11) SC
34 Dalnegroite 1 Tricl. 16.33(2) 42.49(3) 8.564(5) 95.32(4) 90.53(4) 96.43(6) 5878(3) P
35 Dalnegroite ! («Protodalnegroite») 3 Tricl. 8.53(5) 9.16(3) 21.10(2) 93.09(17) 95.70(2) 117.90(5) 1440(10) SC
36 Dewitite 1 Tricl. 8.63253(19) 16.3055(7) 21.8196(8) 75.094(3) 83.631(2) 89.303(2) 2949.18(18) SC
37 Écrinsite 1 Tricl. 8.034(8) 8.533(4) 22.320(9) 90.58(5) 96.96(8) 90.63(7) 1519(2) SC
38 Ferrovorontsovite 2 Cub. 10.2390(7) 1073.43(22) SC
39 Gillulyite 3 Mon. 9.594(2) 5.677(2) 21.401(7) 100.34(3) 1146.5(4) SC
40 Gladkovskyite 3 Trig. 9.6392(2) 6.4560(15) 519.49(12) SC
41 Gungerite 2 Orth. 20.1958(3) 11.5258(2) 20.1430(2) 4688.74(12) SC
42 Hutchinsonite 3 Orth. 10.82(4) 35.39(2) 8.22(2) 3147.6(2) SC
43 Imhofite 3 Mon. 8.776(5) 24.430(3) 5.755(2) 108.40(2) 1170.8(2) SC
44 Lorândite 3 Mon. 12.282(2) 11.240(3) 6.106(2) 104.04(2) 817.8(3) P
45 Luborzâkite 5 Mon. 12.5077(6) 3.8034(2) 16.0517(8) 94.190(4) 761.57(6) SC
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IM O. VI111C1111 Hi 111IC As. no. system o, A b,A c,A a, ° i: A3 thod
46 Meneghinite - Orth. 11.320(1) 24.026(3) 4.1435(7) 1127.0(2) P
47 Parapierrotite (2.0 wt.%As) 4 Mon. 8.0832(5) 19.4057(11) 9.0465(5) 91.908(6) 1418.25(1) SC
48 Parapierrotite (3.7 wt.%As) 4 Mon. 8.066(6) 19.21(4) 9.123(16) 91.81(7) 1412(4) SC
49 Parapierrotite (8.6 wt.%As) 2 Mon. 8.104(17) 19.20(3) 9.05(4) 91.7(2) 1408(7) SC
50 Parapierrotite (15.7 wt.% As) 2 Mon. 8.05(5) 19.39(12) 8.84(6) 92.5(5) 1380(16) SC
51 Philrothite 3 Mon. 8.102(2) 24.845(5) 11.785(4) 132.65(2) 1744.8(2) SC
52 Pokhodyashinite 1 Mon. 23.431(5) 3.996(2) 14.070(3) 110.23(3) 1236.1(8) SC
53 Rebulite 3 Mon. 17.35(3) 7.36(2) 31.94(4) 105.12(2) 3937.4(2) SC
54 Routhierite 1 Tetr. 9.9724(8) 11.295(2) 1123.2(2) SC
55 Routhierite 5 Tetr. 9.967(5) 11.382(10) 1131(1) SC
56 Tennantite-(Zn) 9 Cub. 10.2302(15) 1070.7(3) SC
57 Tsygankoite 7 Mon. 21.362(4) 3.8579(10) 27.135(4) 106.944(14) 2139.19(17) SC
58 Twinnite 1 Mon. 7.9941(14) 19.507(15) 8.6316(15) 91.066(17) 1346(1) SC
59 Twinnite 5 Mon. 7.9846(13) 19.472(2) 8.6127(17) 90.817(17) 1338.9(4) SC
60 Vorontsovite 2 Cub. 10.2956(6) 1091.3(1) SC
61 Vrbaite 3 Orth. 13.391(5) 23.426(15) 11.294(7) 3543(3) SC
62 Weissbergite 1 Tricl. 6.11(3) 6.30(6) 12.00(4) 102.3(4) 100.8(5) 104.4(6) 423(5) SC
63 Zinkenite - Hex. 22.13(5) 4.328(9) 1840(7) SC
Oxides and hydroxides
64 Akhtenskite 9 Hex. 2.8328(7) 4.330(3) 30.09(2) p
65 Arsenolite 6 Cub. 11.0412(7) 1346.01(3) P
66 Asbolane 9 Hex. 2.9602(3) 10.048(5) 76.25(4) P
67 Birnessite 9 Mon. 5.2094(7) 2.8411(3) 7.2924(9) 104.30(2) 104.59(2) P
68 Bixbyite 9 Cub. 9.3665(8) 821.7(2) P
69 Cesárolite 9 Trig. 2.8378(3) 20.536(3) 143.22(3) P
70 Claudetite 6 Mon. 5.2467(6) 13.000(2) 4.5398(5) 94.11(1) 308.85(5) P
71 Coronadite 9 Tetr. 9.923(1) 2.8655(6) 282.16(7) P
72 Cryptomelane 9 Tetr. 9.828(1) 2.8523(3) 275.52(5) P
73 Goethite 9 Orth. 9.9711(8) 3.0225(4) 4.6144(4) 139.086(2) P
74 Hematite 9 Trig. 5.0208(4) 13.735(2) 299.85(5) P
75 Hollandite 9 Tetr. 9.9124(9) 2.9074(5) 285.67(5) P
76 Lithiophorite 9 Trig. 2.8873(4) 28.039(3) 202.44(4) P
77 Magnetite 8 Cub. 8.3990(8) 592.50(17) P
78 Manganite 9 Mon. 5.302(3) 5.190(1) 5.335(1) 114.69(4) 133.37(5) P
79 Manjiroite 9 Tetr. 9.7829(5) 2.8560(2) 273.33(2) P
80 Pyrolusite 9 Tetr. 4.3915(2) 2.8610(1) 55.175(5) SC
81 Ramsdellite 9 Orth. 4.4939(6) 9.2058(9) 2.8493(4) 117.88(2) SC
82 Ranciéite 9 Trig. 2.7871(3) 7.699(4) 51.79(2) P
83 Romanéchite 9 Mon. 13.865(2) 2.8428(5) 9.734(1) 92.472(8) 383.31(6) P
84 Todorokite 9 Mon. 9.8559(9) 2.8478(4) 9.500(1) 95.271(9) 265.53(4) P
Carbonates
85 Azurite 9 Mon. 5.0165(16) 5.856(2) 10.359(5) 92.53(3) 304.0(2) SC
86 Cerussite 9 Orth. 5.1691(6) 8.503(1) 6.102(1) 268.21(5) SC
87 Kutnohorite 9 Trig. 4.8272(5) 16.460(4) 332.16(8) P
88 Malachite 9 Mon. 9.458(1) 11.945(1) 3.2416(4) 98.46(1) 362.24(5) SC
89 Rhodochrosite 9 Trig. 4.7874(6) 15.655(4) 310.74(9) P
Sulfates
90 Anglesite 9 Orth. 8.460(1) 5.3908(6) 6.966(1) 317.71(6) SC
91 Beavente-(Cu) 9 Trig. 7.1888(7) 17.096(6) 765.1(2) P
92 Brochantite 9 Mon. 13.091(1) 9.820(1) 6.0211(8) 103.73(1) 751.90(5) P
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in native arsenic and arsenolite/claudetite and at their contacts with gangue minerals and native gold (Fig. 7d). The chemical composition of ar-senopyrite from assemblage no. 6 is studied in detail (Murzin et al., 2011). In our samples from the dumps of the southern open pit, arsenopyrite forms prismatic crystals up to 1 cm (Fig. 9b) and steel gray aggregates up to 6 * 5 cm in size. The mineral is identified by chemical composition and XRD data (Table 3).
Bismuthinite Bi2S3 was found as rare anhedral grains up to 80 pm across in magnetite of assemblage no. 8. The chemical composition of the mineral (Table 4) is close to ideal Bi2S3.
Bornite Cu5FeS4 together with dominant chal-copyrite occurs in variable amounts in ores developed in the skarn zones in diorites. Both sulfides compose veinlets and pockets 1-10 mm in size and are confined to areas of epidote-calcite, epidote-actinolite-calcite and quartz-sericite-calcite composition. The mineral was identified by chemical composition (Vikentyev et al., 2016). In our samples, bornite was found only in assemblage no. 9 as very rare small (<20 pm) inclusions in calcite and quartz. Its chemical composition is stoichiometric (Table 4).
Chalcopyrite CuFeS2is a common mineral of the deposit. It is identified in polymetallic mineralization of wollastonite skarns. It occurs as large (up to 5 mm) aggregates and small (up to 0.1 mm) crystals in quartz veinsin beresites and listvenites. In breccia matrix, chalcopyrite forms anhedral grains from 10 pm to 2-3 mm in size in carbonates; it often contains inclusions of sulfosalts, galena, and sphalerite (Sazonov et al., 1991a). In our samples of carbonate breccias, chalcopyrite was found only in assemblages nos. 1 and 6. It occurs more often in assemblage no. 8, where it forms aggregates of distorted tetrahe-dral crystals up to 0.5 cm across and golden yellow aggregates and is observed together with andradite, calcite, magnetite, arsenopyrite, fahlores, pyrite, and sphalerite (Fig. 9c). In the supergene zone, chalcopyrite occurs as fine oxidized grains in quartz-cal-cite aggregates. Chalcopyrite is a main source of Cu for supergene carbonates (azurite, malachite) and sulfates (beaverite-(Cu), brochantite, chalcanthite). The chemical composition of chalcopyrite is close to ideal (Table 4). The parameters of its tetragonal unit cell are given in Table 3.
Cinnabar HgS was described as a very rare ore mineral (Sazonov et al., 1991a). Its grains reach
Fig. 9. Elements and sulfides of the Vorontsovskoe deposit, part I:
a - crystalline aggregate of native gold in calcite; b - aggregate of prismatic arsenopyrite crystals; c - aggregates of golden yellow chalcopyrite crystals on calcite and andradite; d - red fine-grained cinnabar in carbonate matrix with stibnite; e - black powdery djurleite and covellite aggregates on galena; f - lead gray isometric galena crystals in quartz matrix; g -dark red platy getchellite crystals in calcite-dolomite matrix with yellow wakabayashilite; h - dark brown greigite crusts on calcite-dolomite marble; i - yellow powdery hawleyite on sphalerite;j - steel gray lollingite with massive brown sphalerite in white calcite; k - iron black metacinnabar grain (in center) in matrix of calcite, dolomite, and realgar; 1 - veinlet of bright yellow orpiment with bright red realgar in native arsenic.
Collections of Museum «Shtufnoi Kabinet», Severouralsk (a-d), A.V. Kasatkin (e-k), V.V. Levitskiy (1). Photo: T.V. Pashko (a, b), M.V Tsyganko (c, d), A.D. Kasatkina (e-k), V.V. Levitskiy (1).
0.1-0.3 mm in size and occur together with realgar in thin (1-2 mm) carbonate veinlets in limestone breccias or are included in breccia carbonates in assemblage with realgar and Hg-bearing sphalerite. The chemical composition of cinnabar is close to stoichiometric
(Sazonovetal., 1991a). According to our observations, cinnabar is rare in assemblage no. 1 and is abundant in assemblages nos. 2 and 3, where it forms grains up to 0.2 mm across. In assemblage no. 4, cinnabar is one of major ore minerals and occurs as fine-grained dark red
An. no. As. no. Mineral name Mn Fe Cu Zn Ag Hg Pb Bi As Sb Te S Total Formula
1 1 Acanthite - - - - 86.92 - - - - - - 12.68 99.60 Ag2.01S0.99
2 7 Alabandite 63.18 - - - - - - - - - - 37.04 100.22 Mn! 00S1.00
3 8 Bismuthinite - - - - - - - 81.44 - - - 18.76 100.20 Bi2.00s3.00
4 9 Bornite - 11.23 63.45 - - - - - - - - 25.65 100.33 cu4.99Fel.01s4.00
5 8 Chalcopyrite - 30.56 35.15 - - - - - - - - 35.12 100.83 cul.01Fel.00s2.00
6 2 Cinnabar - - - - - 78.66 - - - - - 7.44 99.97 Hgo.98(So.58Seo.44)l.02
7 Coloradoite - - - - - 61.45 - - - - 39.44 - 100.89 Hgl.00Te1.00
8 9 Covellite - - 65.23 - - - - - - - - 35.12 100.35 CU0.97S1.03
9 6 Cubanite - 41.29 23.69 - - - - - - - - 35.10 100.08 CUl.oiFe2.OlS2.98
10 9 Djurleite - - 79.03 - - - - - - - - 20.46 99.49 CU31.06S15.94
11 7 Duranusite - - - - - - - - 91.00 - - 9.61 100.61 AS4.01S0.99
12 9 Galena - - - - - - 86.62 - - - - 13.45 100.07 Pb1.00S1.00
13 4 Gersdorfite - 1.06 - - - - - - 44.03 - - 19.82 100.92 (Nio.64COo.3sFeo.03)l.03ASo.96Sl.ol
14 1 Getchellite - - - - - - - - 26.06 41.80 - 33.18 101.04 Asi.oiSb 0.99S3.00
15 1 Greigite - 56.78 - - - - - - - - - 42.33 99.11 Fe3.05s3.95
16 6 Hessite - - - - 64.95 - - - - - 34.92 - 99.87 Ag2.06Teo.94
17 8 Ikunolite - - 0.04 - - - 1.89 82.47 - - 5.86 8.51 99.56 Bi3.8lPbo.09CUo.ol(S2.56Teo.44Seo.lo)3.10
18 Jalpaite - - 14.01 - 70.21 - - - - - - 13.89 98.11 Ag2.99cul.01sl.99
19 8 Joseite-A - - - - 0.15 - 0.50 79.72 - - 11.73 5.81 99.04 Bi3.97Pb„.„3Ag„.„iTe„.96(Si.89Se„,5)2.04
20 Lollingite - 28.57 - - - - - - 69.44 - - 1.28 99.29 Fel.04Asl.88s0.08
21 4 Metacinnabar - - - 10.85 - 71.60 - - - - - 17.25 99.70 (Hgo 67Zllo 31)0.98S 1.01
22 4 Metacinnabar 1.70 - - 15.01 - 64.12 - - - - - 18.50 99.33 (Hgo 55ZII0 40-MII0 05)l.00Sl.00
23 2 Orpiment - - - - - - - - 59.16 1.45 - 38.81 99.42 ( AS 1 96 Sbo. 03) 1.99 S3.01
24 2 Pararealgar - - - - - - - - 69.48 - - 29.85 99.33 AS3.99S4.01
25 4 Picotpaulite - 27.21 - - - - - - - - - 23.86 100.36 Tlo.98Fel.99s3.03
26 Realgar - - - - - - - - 68.89 - - 29.87 98.76 AS0.99S1.01
27 4 Sphalerite 3.43 - - 45.04 - 23.10 - - - - - 27.73 99.30 (Zn0.80Hg0.l3Mn0.07)l.00Sl.00
28 Sphalerite - - - 66.94 - - - - - - - 32.80 99.74 Zn1.00S1.00
29 4 Stibnite - - - - - - 0.23 - 0.76 70.69 - 27.90 99.58 (Sbi.99ASo.03)2.02S2.98
30 8 Tetradymite - - - - - - - 59.14 - - 36.70 4.15 100.32 Bi2.0lTe2.04(S0.92Se0.03)0.95
31 1 Wakabayashilite - - - - - - - - 56.17 6.51 - 36.42 99.1 AS9.2sSbo.66S14.O6
Note. Here and in Tables 5, 7, 9, 10, An. no. - number of analysis; As. no. - number of mineral assemblage (see Table 2). The analytical total includes (wt. %) an. 6 - 13.87 Se; an. 13 - 13.15 Co, 22.86 Ni; an. 17 - 0.79 Se; an. 19 - 1.13 Se; an. 25 - 49.29 Tl; an. 30 - 0.33 Se. Analyses 7 and 26 are the average values of 15 and 20 analyses of coloradoite and realgar from various assemblages. Dash - the content of element is below detection limit.
Samples: Vor-8bis-2-an. 1; Vor-10-1-an. 2, 11; Kasl72 #11 - an. 3, 17, 19, 30; Vor-08/20-11-an. 4; 1066A-an. 5; Vor-03/16-6-6 - an. 6; Vor-06/20-11 - an. 8, 10; Vor-01/16-lb - an. 9; Vor-06/20-5 - an. 12; Vor-3 - an. 13, 25; 862G - an. 14; 1099G - an. 15; Vor-01/16-la - an. 16; Vor-08/20-8 - an. 18; 534L - an. 20; 973M -an. 21; Vor-08/16-11-1 - an. 22, 27; Vor-b/n-9 - an. 23; Vor-08/20-7 - an. 24; 1221S - an. 28; SK-18-19 - an. 29; 610V- an. 31.
The mineral formulas are recalculated to atom sum of two (alabandite, cinnabar, galena, coloradoite, covellite, metacinnabar, realgar, sphalerite), three (acanthite, hessite, lollingite), four (chalcopyrite), five (bismuthinite, duranusite, getchellite, orpiment, stibnite, tetradymite), six (cubanite, gersdorffite, jalpaite, picotpaulite), seven (greigite, ikunolite, joseite-A), eight (pararealgar), ten (bornite), 24 (wakabayashilite) and 47 (djurleite).
aggregates in carbonates, quartz, and baryte in assemblage with Hg-bearing sphalerite, stibnite, metacinna-bar, and realgar (Fig. 9d). In assemblage no. 2, cinnabar contains significant amount of Se (13.9 wt. %) (Table 4). The parameters of the hexagonal unit cell of cinnabar from assemblages nos. 1 and 4 are given in Table 3.
Coloradoite HgTe was identified as single grains up to 0.1 mm across intergrown with native arsenic and an unidentified Ag telluride (hessite?) in limestone (Sazonov et al., 1991a) and as aggregates 40-50 pm in size in «pierrotite» in assemblage with native gold (Murzin, Varlamov, 2010). In our samples, coloradoite is present in all mineral assemblages of carbonate breccias except for assemblage no. 6. This telluride typically forms rare rounded grains 5-40 pm in size embedded in calcite and dolomite. It is more abundant in assemblage no. 2 and ubiqiutous in assemblage no. 4. In the latter assemblage coloradoite composes large anhedral aggregates up to 0.12 * 0.06 mm in calcite (Fig. 8b), dolomite, and realgar, elongated grains up to 0.04 mm at the contact of orpiment and stibnite (Fig. 8c) and inclusions up to 0.05 mm in stibnite and in-tergrowths with Hg-bearing sphalerite and zinkenite. Coloradoite is also associated with aktashite, andorite, native arsenic, cinnabar, native gold, guettardite, pyrite, routhierite, and tennantite-(Zn). The mineral contains no trace elements in chemical composition (Table 4). The parameter of the cubic unit cell of coloradoite from assemblage no. 4 is given in Table 3.
Covellite CuS overgrows sphalerite with small chalcopyrite inclusions in garnet skarn samples from the supergene zone (Vikentyev et al., 2016). We found covellite in assemblage no. 9 in oxidized quartz aggregates collected at the dumps of the southern open pit. Covellite is intimately intergrown with djurleite and forms black powdery crusts on galena in assemblage with beaverite-(Cu), malachite, and gypsum (Fig. 9e). Covellite was identified by optical properties, chemical composition (Table 4) and PXRD pattern (Table 3).
Cubanite CuFe2S3 was found in one sample from assemblage no. 6 as inclusions up to 20 pm in size in dolomite and native arsenic together with chalcopyrite, pyrite, sphalerite, and tetrahedrite-(Zn). The mineral was identified based on chemical composition (Table 4) and optical properties (light brown color in reflected light, strong anisotropy in pinkish brown and grayish blue tones).
Dimorphite As4S3 was mentioned by Stepanov et al. (2017) as a low-temperature mineral of the breccia matrix on the basis of three chemical analyzes, which
approximately correspond to formula As4S3. This finding requires confirmation by XRD, because, according to our analytical experience, the overestimation of As relative to S can be caused by microinclusions of native arsenic in realgar.
Djurleite Cu31S16 was found as black powdery crusts overgrowing galena on quartz aggregate in samples with assemblage no. 9 collected from the dumps of the southern open pit (Fig. 9e). Djurleite occurs together with covellite, beaverite-(Cu), malachite, and gypsum. The mineral was identified by EMPA (Table 4) and PXRD data. The strongest reflections of the PXRD pattern are [d, A (/)]: 3.27 (30), 3.05 (20), 2.82 (10), 2.63 (10), 2.48 (10), 2.37 (90), 1.96 (100), 1.88 (100). The parameters of the monoclinic unit cell are given in Table 3. In fresh polished thin sections, djurleite looks light gray with a bluish tint, but is quickly covered by an iridescent film.
Duranusite As4S was found in assemblages nos. 2 and 7. It occurs as coarse prismatic crystals up to 0.2 mm in size enclosed in carbonates of breccias (Fig. 8d). It is locally rimmed by tilasite and contains inclusions of native arsenic. Duranusite formed prior to native arsenic but after realgar and orpiment, being a kind of their intermediate alteration product. Duranusite has a deep red color and a metallic luster. In reflected light, the mineral is light gray, with very weak bireflectance; it is distinctly anisotropic in yellowish tones, with red internal reflections. The chemical composition is stoichiometric (Table 4). This is the first finding of duranusite in the Russian Federation.
Galena PbS was noted as a rare ore mineral in altered wollastonite skarns (Sazonov et al., 1991a; Vikentyev etal., 2016). Together with sphalerite, it forms aggregates up to 3 cm across in greenish rocks, which consist of wollastonite partly replaced by epidote, ac-tinolite, and chlorite. In carbonate breccias, it occurs as rare small anhedral grains up to 0.5 mm in size and occasionally as small inclusions in pyrrhotite. Galena is often intergrown with sphalerite, Pb sulfosalts, and tet-rahedrite and replaces arsenopyrite, sphalerite (along cleavage), and pyrite (along microfractures).
In our samples, galena was found as a rare accessory mineral of carbonate breccias and skarns in assemblages nos. 1, 4, 6, and 8. In assemblage no. 9 of the oxidation zone, it is more abundant and forms isometric lead gray crystals up to 1 cm in size (Fig. 9f), as well as elongated aggregates up to 7 cm in size in sphalerite and veinlets with pyrite in quartz. In off-balance ore stockpile no. 2, we collected several samples of white massive carbonate-quartz aggregates with
lead gray galena veins up to 3 mm thick and several centimeters long. These veins contain inclusions of rare Ag- and Te-bearing minerals (hessite, benleonar-dite, tsnigriite) and geocronite (Fig. 1 Id). In other samples, galena forms aggregates with rare Pb sulfosalts: boulangerite, heteromorphite, plagionite, and sem-seyite (Fig. lli). The chemical composition of galena is close to stoichiometric (Table 4); its XRD data are shown in Table 3.
Gersdorfite NiAsS with a significant Fe content was noted as single 10-20 pm inclusions in pyrite (Vi-kentyev et al., 2016). We found this mineral in assemblage no. 4 as rare cubic crystals up to 10 pm in cal-cite. In reflected light, gersdorfite is white, isotropic. It contains Co and Fe in chemical composition (Table 4).
Getchellite AsSbS3 was found in samples from the main ore stockpile (Kasatkin, 2019) as red lamellar aggregates up to 2 cm embedded in calcite-dolomite marble (Fig. 9g). The mineral is transparent and has an adamantine luster and a perfect cleavage parallel to {001}. It belongs to assemblage no. 1 and is associated with orpiment, pyrite, realgar, stibnite and waka-bayashilite. The chemical composition (Table 4) is stoichiometric; the parameters of the monoclinic unit cell (Table 3) correspond to getchellite. This is the first reliable find of this mineral in the Russian Federation.
Greigite Fe3S4 was first mentioned amid minerals associated with clerite (Murzin et al., 1996). Later, it was noted as anhedral aggregates and, less often, crystals up to 0.15 mm in size enclosed in gangue minerals of the breccia matrix and, locally, rimmed by realgar. Greigite contains Sb and As in chemical composition (Murzin, Varlamov, 2010). We collected samples with macroscopic greigite in the dumps of the southern open pit. This mineral occurs as dark brown crusts and sooty black films on calcite and dolomite and contains inclusions of native arsenic, orpiment, pyrite, realgar, stibnite, and baryte (Fig. 9h). In reflected light, it looks yellowish brown, brighter than As sulfides, but much darker than pyrite and stibnite in its lightest position. Greigite was identified by chemical composition (Table 4) and XRD data (Table 3). It was also found in carbonate breccias from assemblage no. 2 with gungerite, orpiment, and arsenic (Fig. 16c).
Hawleyite CdS was found in samples from the dumps of the southern open pit, where it occurs as yellow powdery veinlets overgrowing sphalerite and galena in assemblage no. 9 (Fig. 9i). Hawleyite is dark gray in reflected light, but looks lighter than sphalerite. At the contact with galena, it acquires a distinct greenish tint. The mineral is isotropic, with yellow inter-
nal reflections. Its chemical composition is as follows (wt. %, average of three analyses): 68.72 Cd, 8.25 Zn, 23.45 S, total 100.42. The empirical formula calculated on the based on two atoms is (Cdo.83Zn0.i7)i.ooSi.oo- The parameter of the cubic unit cell is given in Table 3.
Hessite Ag2Te was determined in assemblage no. 6 as rare isometric grains up to 15 pm in size in gangue minerals of breccias. It was also identified in calcite-dolomite-quartz aggregates with galena and sphalerite collected at off-balance ore stockpile no. 2. It forms inclusions up to 10 pm in galena and is associated with benleonardite, geocronite, and tsnigriite. The chemical composition of hessite is close to stoichiometric (Table 4).
Ikunolite Bi4(S,Se)3 represented by a Te-bearing variety was found as single intergrowths with lillianite up to 20 pm enclosed in magnetite from assemblage no. 8. In reflected light, both ikunolite and lillianite are white, but the former has much weaker anisotropy (in faded brownish tones). The chemical composition of ikunolite is given in Table 4.
Jalpaite Ag3CuS2 forms tiny prismatic crystals up to 20 x 10 pm in chalcopyrite (Fig. 8e) in assemblage with cupropolybasite, polybasite, pyrite, galena, sphalerite, tetrahedrite-(Fe), calcite, and quartz. The mineral was identified by chemical composition (Table 4). In reflected light, jalpaite looks gray; it is weakly anisotropic.
Joseite-A Bi4TeS2 forms rare intergrowths with pavonite in magnetite from assemblage no. 8 (Fig. 21f). The size of the joseite-A grains does not exceed 20 pm. In reflected light, it is creamy white at the contact with pavonite. After several weeks, the joseite-A grains in polished sections are covered by a thin oxide film with a characteristic irridescence. Joseite-A contains a small amount of Se (Table 4).
Lollingite FeAs2 was first found as rosettes and acicular crystals in assemblage with native arsenic and arsenopyrite (Vikentyev et al., 2016). In our samples from the dumps of the northern open pit, the large (up to 3 cm) aggregates of steel gray lollingite are identified in massive brown sphalerite of white calcite-dolo-mite marble (Fig. 9j). Lollingite has a low S content: up to 1.3 wt. % (Table 4). The parameters of the or-thorhombic unit cell are given in Table 3.
Metacinnabar HgS was identified as a rare mineral in assemblages nos. 1-3. It differs from cinnabar by black color, the absence of cleavage, as well as optical properties. In reflected light, metacinnabar is light gray, isotropic and has no internal reflections. In assemblage no. 4, it occurs more often and composes
larger grains (up to 0.5 * 0.5 cm) in carbonates (calcite, dolomite) associating with cinnabar, coloradoite, pyrite, realgar, sphalerite, stibnite, aktashite, routhierite, and baryte (Fig. 9k). It has high Zn contents (Table 4). The isomorphic incorporation of Zn in metacinnabar is also reflected in a PXRD pattern. Each strong reflection ([d, A (/)]: 3.318(100), 2.865(80), 2.028(20), 1.735(80), 1.438(20), 1.325(30), 1.175(20), 1.106(20)) is lower by 0.2-0.7 A than the corresponding reflection of a synthetic cubic HgS phase. Thus, the unit cell volume of metacinnabar from the Vorontsovskoe deposit (Table 3) is significantly smaller than the volume of the synthetic phase: 188 A3 versus 200 A3. In some cases, the Zn-Mn-bearing metacinnabar forms cubic crystals up to 30 pm or the outer zones 0.08-0.1 mm thick aroundthe Hg-Mn-bearing sphalerite (Fig. 8f).
The chemical compositions of both sulfides are given in Table 4. Vasiliev (2011), who studied solid solutions in the Zn-Hg-S system, concluded on the absence of a continuous isomorphic series in cubic ZnS-HgS sulfides and a miscibility gap in an intermediate range from (Zn0752Hg0 248)S to (Hg0539Zn0461)S. Our data confirm these conclusions; moreover, metacinnabar from the Vorontsovskoe deposit contains 15wt.%Zn (or 15.4wt.% when recalculated without Mn and normalized to 100 wt. %), which is close to the maximum possible Zn concentration in metacinnabar (17.7 wt. %).
Molybdenite MoS2 was recognized in bornite-chalcopyrite ores from diorite skarn zones (Vikentyev et al., 2016). We found it as small oval inclusions up to 20 pm in calcite with pyrite, realgar, sphalerite, dalne-groite, christite, coloradoite, metacinnabar, routhierite, and philrothite in assemblage no. 1. Optically, molybdenite is reliably identified by very strong (especially, in immersion) bireflectance typical for this mineral and very intense anisotropy in light and dark gray and deep black tones. The chemical composition of the mineral is stoichiometric (wt. %): 60.14 Mo, 39.17 S, total 99.31. Its empirical formula based on three atoms is
Moi.02S1.98-
Orpiment As2S3 is abundant in brecciated limestones and is always associated with more common realgar. The macroscopically visible orpiment aggregates are locally responsible for a lemon yellow color of the ore. The individual anhedral orpiment grains are rare. Its tiny acicular crystals up to 0.3 mm long enclosed in limestone fragments are more abundant. The mineral was identified by chemical composition and XRD data. It contains Sb up to 4.4 wt. % (Sazonov et al., 1991a). Later, orpiment was found in the carbonate
breccia matrix as individual grains up to 1 mm, locally, with realgar inclusions (Murzin, Varlamov, 2010; Vikentyevetal.,2016).
In our samples, orpiment in all seven mineral assemblages is confined to carbonate breccias, where it makes a matrix for gangue minerals together with pyrite, realgar and, locally, arsenopyrite, and stibnite. In assemblage no. 3, orpiment is one of the major ore minerals. In assemblage no. 6, it occurs together with realgar forming spectacular yellow red veins in native arsenic nodules (Fig. 91). In our samples, orpiment contains only <1.5 wt. % Sb (Table 4). The calculated parameters of the monoclinic unit cell are given in Table 3.
Pararealgar As4S4was found in samples from offbalance ore stockpile no. 2 as bright orange powdery aggregates, which partly replace bright red realgar on fragments of carbonate breccias (Fig. 10a). Pararealgar belongs to assemblage no. 2. The associated ore minerals include vorontsovite, ferrovorontsovite, galkhaite, boscardinite, ecrinsite, routhierite, stibnite, cinnabar, coloradoite, metacinnabar, pyrite, and sphalerite. The gangue minerals are calcite, Mn-bearing dolomite, and baryte. The identification of pararealgar is confirmed by both EMPA (Table 4) and SXRD (Table 3). Optically, pararealgar is similar to realgar. In reflected light, it looks dull gray; the bireflectance is distinct. Anisotropy is strong and is better observed in slightly crossed-polarized light. In completely crossed-polar-ized light, it is masked by abundant yellow and orange internal reflections. Pararealgar is known as a product of light-induced transformation of realgar (Bonazzi et al., 1995, Bindi et al., 2003) in oxidized contiditions. Therefore, it is likely that pararealgar formed directly in the ore stockpile. This is the first reliable find of pararealgar in the Russian Federation.
Picotpaulite TlFe2S3 is the only sulfide with species-defining T1 found at the deposit. It was identified in two polished sections in assemblages nos. 3 and 4 as rare small (no more than 15 * 12 pm) inclusions in gangue minerals of breccias (calcite, dolomite, baryte, clinochlore) and intergrowths with realgar. In assemblage no. 3, picotpaulite is also associated with gladkovskyite, native gold, and routierite and, in assemblage no. 4, it occurs together with chabourneite, christite, cinnabar, coloradoite, metacinnabar, orpiment, parapierrotite, and pyrite (Fig. 8g). In reflected light, the mineral is creamy pinkish and, in aggregates with realgar, it looks much brighter than the latter. Bireflectance is distinct. Picotpaulite is strongly anisotropic in gray-violet tones. Its chemical composition is
Fig. 10. Sulfides of the Vorontsovskoe deposit, part II:
a - bright orange pararealgar crusts on deep red realgar in carbonate breccia; b - pyrite crystal in carbonate matrix with pigeonite; c - dark red realgar crystals with gray stibnite in a cavity of silicified limestone; d - massive yellow-brown sphalerite; e - radial aggregates of lead gray stibnite crystals on dolomite and calcite in assemblage with golden yellow pyrite; f - acicular stibnite crystals up to 1 cm in cavities of carbonate matrix with bright red realgar; g - bright yellow fibrous wakabayashilite crystals in calcite and dolomite with dark pyrite and stibnite; h - bright yellow wakabayashilite in breccia; i - yellow fibrous wakabayashilite colored by bright red powdery realgar.
Collections of A.V. Kasatkin (a, e, g, h), Museum «Shtufnoi Kabinet», Severouralsk (b, d, f, i), VV Levitskiy (c). Photo: A.D. Kasatkina (a, e, g, h), M.V. Tsyganko (b, d, f, i), VV. Levitskiy (c).
close to the ideal formula TlFe2S3 (Table 4). This is the first finding of picotpaulite in the Russian Federation.
Pyrite FeS2 is the major ore mineral of various rocks of the deposit. In metasomatites, its content is 1-10 %, but often is <1 %. Several morphological varieties of pyrite of various sizes are known. Abundant pyrite grains of 0.01-0.1 mm in size occur as fine inclusions in other minerals; metacrystals up to several millimeters in size are less common. The calcite-gros-sular skarns host pyrite crystals up to 1 cm in size. In quartz veins in beresites and listvenites, pyrite is characterized by two generations: cubic pyrite-1 crystals 0.5-1 mm (rarely up to 5 mm) in size and small (about
0.1-0.2 mm) pyrite-2 crystals of complex morphology. Pyrite typically contains numerous microinclusions of other ore minerals, mainly, chalcopyrite and pyrrhotite. Together with magnetite, pyrite is the only ore mineral of unaltered skarns, where it occurs as irregular interstitial aggregates up to several millimeters in size. In altered skarns, pyrite forms large (1-10 mm) aggregates and often crystals of complex morphology in quartz-calcite matrix. It forms dissemination of crystals 0.1-0.3 mm (locally, up to 2 cm) in size in pro-pylitized rocks or in matrix of ore breccias. Pyrite is the major ore mineral of altered volcanosedimentary rocks, where its content, together with arsenopyrite,
reaches 20-30 wt. %. Pyrite forms metacrystals of 0.05-3 mm in size and replaces shell walls of mollusks or rock-forming minerals. Pyrite is extremely abundant in carbonate breccia matrix in form of metacrystals and crystal aggregates up to 1.5 cm in size (Sazonov et al., 1991a). In a sample from the dumps of the southern open pit, we found a well-formed pyrite crystal of an atypical light silvery color 25 x 25 mm in size in an aggregate of calcite, dolomite, and pigeonite (Fig. 10b). Pyrite of the deposit contains up to 1.1 wt. % Co, Ni, and As (Sazonov et al., 1991a; Murzin, Varla-mov, 2010; Vikentyev et al., 2016).The results ofXRD analyses of pyrite from mineral assemblages nos. 1 and 9 are given in Table 3.
Pyrrhotite Fe1-xS is a rare mineral of the deposit (Sazonov et al., 1991a; Vikentyev et al., 2016). It was found as inclusions up to 0.5 mm in sphalerite and at the contact of sphalerite and galena in wollastonite skarns.Pyrrhotite together with chalcopyrite forms aggregates up to several centimeters in altered skarns. In the breccia matrix, it occurs as rare crystals up to 0.1 mm in carbonates, rounded or drop-like inclusions up to 0.05 mm in size in earlier pyrite, arsenopyrite or sphalerite.
Realgar AsS is the major ore mineral in breccias, where it is disseminated in limestone fragments and is responsible of a reddish color of breccia. Its small-sized (up to 0.2 mm) and larger (up to 5 mm) individuals are characterized by angular anhedral morphology and occur between carbonate. Realgar locally fills microfractures in pyrite metacrystals. The largest realgar aggregates often contain inclusions of pyrite, sphalerite, and T1 and Hg sulfosalts (Sazonov et al., 1991a). The free-standing realgar crystals up to 0.5 cm in size were found at the main ore stockpile (Fig. 10c). According to Murzin and Varlamov (2010), realgar contains Sb (up to 1.6 wt. %). We found that realgar melts during the EMPA under standard conditions for sulfides and sulfosalts (WDS, 25 kV, 20 nA, 1 pm). Satisfactory analytical conditions for chemical analyses of realgar were achieved at a lower accelerating voltage of 15 kV and a beam rastering at a 10 * 10 pm area. In most assemblages, realgar contains only As and S (Table 4). The parameters of the monoclinic unit cell are given in Table. 3.
Sphalerite ZnS is one of the major ore minerals of the deposit. Together with galena, it forms aggregates 2-3 cm in size in wollastonite skarns. In altered skarns, sphalerite occurs as veins or inclusions in pyrite and typically contains small chalcopyrite and pyr-rhotite grains. In breccia matrix, it forms euhedral and
anhedral aggregates 0.05-0.4 mm in size enclosed in carbonates or quartz and intergrown with baryte, pyrite, and fahlores. Sphalerite often contains (up to) Hg (23.1 wt. %), Mn (4.9 wt. %), Fe (8.5 wt. %), Cd (1.3 wt. %), Cu (0.7 wt. %), and Ag (0.4 wt. %) (Sazonov et al., 1991a; Murzin, Varlamov, 2010). The Mn-bearing sphalerite (up to 7.6 wt. % Mn) was described as rounded and oval inclusions up to 50-70 pm in size in native arsenic and arsenopyrite (Murzin et al., 2011).
Samples from the dumps of the southern open pit and off-balance ore stockpile no. 2 contain dark green sphalerite aggregates up to 20 cm in size with galena inclusions. This sphalerite contains only Zn and S. The yellow-brown sphalerite from samples of the main ore stockpile (Fig. 10d) is also nearly trace element-free (Table 4, an. 28). The parameter of its cubic unit cell is given in Table 3. In assemblage no. 4, the Hg-Mn-bearing sphalerite grains up to 0.2 mm in size are enclosed in carbonates (dolomite, calcite) and are often surrounded by rims of Zn-Mn-bearing metacinnabar up to 40 pm thick (Fig. 8f). The chemical composition of this sphalerite is given in Table 4, an.27. In reflected light, Hg-Mn-bearing sphalerite shows dark red internal reflections.
Stibnite Sb2S3 is widely abundant at the deposit. In ore breccias, it occurs as acicular crystals up to 0.2 mm long or anhedral aggregates up to 3 mm, locally forms intergrowths with zinkenite and chalcosti-bite and contains inclusions of native gold and native arsenic. Stibnite was determined by its optical properties and chemical composition. It often contains As (up to 3.5 wt. %) (Sazonov et al., 1991a). Murzin and Varlamov (2010) described this mineral as rare grains and anhedral aggregates in carbonates -0.1 mm in size, which it is often intergrown with Hg and T1 sulfosalts. It contains up to 7.5 wt. % As.
In a large specimen from ore zone of the northern open pit, stibnite forms spectacular radial aggregates up to 2 cm in diameter of lead gray prismatic and acicular crystals, which are located in an open cavity of the dolomite-calcite rock in assemblage with pyrite and arsenopyrite (Fig. 10e). In assemblage no. 4, stibnite is the major ore mineral in addition to pyrite and realgar. It forms acicular crystals up to 1 cm in size and irregular grains intergrowing with orpiment and realgar in the dolomite-calcite rock (Fig. 10f). Stibnite contains numerous small inclusions of various Pb-Cu-Ag-bear-ing sulfosalts (andorite, tennantite-(Zn), zinkenite), coloradoite, and native arsenic as well (Fig. 8h). The chemical composition of stibnite in given in Table 4 and its XRD data are provided in Table 3.
Tetradymite Bi2Te2S was found in skarns in assemblage no. 8 as rounded grains up to 40 pm in size at the contact with magnetite and calcite (Fig. 8i). The chemical composition of tetradymite is close to stoichiometric (Table 4).
Wakabayashilite (As,Sb)6As4S14 was first identified in samples collected in the main ore stockpile (Ka-satkin, 2019). It belongs to assemblage no. 1 and is associated with cinnabar, getchellite, orpiment, pyrite, realgar, stibnite, and rare Tl- and Hg-bearing sulfosalts, which occur as tiny inclusions in wakabayashilite: boscardinite, chabourneite, coloradoite, dalnegroite, ecrinsite, parappierrotite, routhierite, etc. Wakabaya-shilite is one of the most spectacular minerals of the deposit. It occurs as columnar and fibrous aggregates and irregular crystals up to 2 cm in size in calcite-do-lomite marble (Figs. 10g-i). Wakabayashilite is bright yellow to yellow-orange with a strong silky luster. Perfect cleavage is observed along {010}, {100}, and {101}. In reflected light, the mineral is grayish white; it is weakly anisotropic with abundant internal lemon yellow reflections. Wakabayashilite was also detected in assemblage no. 2, where it forms rare small (no more than 50 pm in size) inclusions in carbonates together with vorontsovite and ferrovorontsovite. The chemical composition (Table 4) and the orthorhombic unit cell parameters of wakabayashilite from both assemblages (Table 3) correspond to this mineral.
Sulfosalts
This mineral group is unambiguously of great interest, because it is the largest in terms of a number of mineral species identified at the Vorontsovskoe deposit. Sulfosalts include all Vorontsovskoe type locality minerals and most first findings of previously unknown minerals at the territory of the Russian Federation. The most sulfosalts are found in carbonate breccias characterized by the ultimate variety of mineral species.
Aktashite Cu6Hg3As4S12 was first described by Sa-zonov et al. (1991a) as anhedral, rarely euhedral light gray aggregates up to 0.05 mm across in limestones. The mineral was identified by its optical properties and chemical composition. It contains Zn (up to 2.0 wt. %), Cd (up to 0.9 wt. %), and Fe (up to 0.5 wt. %). Murzin and Varlamov (2010) reported on the aktashite grains up to 0.15 mm in size intergrown with sphalerite, baryte, chabourneite, and other Tl sulfosalts, which were found in the carbonate matrix and siliceous fragments of breccias. The mineral contains up to 3.9 wt. % Zn and up to 2.8 wt. % Sb.
We identified aktashite in five mineral assemblages. Its largest aggregates (up to 0.2 mm in size) are typical of assemblage no. 1 at the contact of orpiment and gangue minerals (prehnite, calcite) and as intergrowths with sphalerite (Fig. 11a). In assemblage no. 4, aktashite occurs as anhedral grains up to 50 pm across enclosed in carbonates (calcite, dolomite) and is observed together with cinnabar, coloradoite, para-pierrotite, routhierite, sphalerite and stibnite. In other assemblages, aktashite composes individuals 2030 pm in size in gangue minerals of breccias. In reflected light, the mineral looks light gray, brighter than orpiment and sphalerite, but darker than all other neighboring ore minerals. In general, the effects of anisotropy in the air are weak, but, in some grains of aktashite from assemblage no. 1, they are distinct, in brownish tones, much stronger in immersion. According to chemical composition (Table 5), aktashite contains Zn, Fe, and Mn (all isomorphic to Hg) and up to 2.6 wt. % Sb (= 0.35 apfu) (a gruzdevite component). The parameters of the hexagonal unit cell (Table 4) correspond to aktashite.
Nowackiite CugZn3As4S12, a Zn analog of aktashite, was determined in two specimens from assemblages nos. 1 and 4. In sample Vor-SS-6, nowackiite occurs as tiny (less than 10 pm in size) grains in di-opside and pyrite and is associated with ecrinsite, native gold, orpiment, parapierrotite, realgar, baryte and fluorapatite. In sample VD-7.1b, a small nowackiite zone (Table 5) was detected in a 40-pm inclusion of Zn-rich aktashite in prehnite with parapierrotite, pyrite, and realgar. Optically, nowackiite is indistinguishable from aktashite. This mineral was found for the first time in the Russian Federation.
Andorite AgPbSb3S6 was found in polymineral sulfosalt veinlets up to 5 mm thick in limestones and as small inclusions in bournonite (Vikentyev et al., 2016). One chemical analysis given in this work shows a deficiency of Ag (9.3 wt. % = 0.73 apfu) and the presence of Fe (2.8 wt.% = 0.43 apfu) and Cu (1.0 wt. % = 0.13 apfu).
We identified andorite in assemblages nos. 1 and 4, where it forms small (<15 pm in size) inclusions in stibnite with orpiment (Fig. lib), coloradoite, realgar, tennantite-(Zn), zinkenite, and native arsenic. In reflected light, andorite is white, almost indistinguishable from the host stibnite in its lightest position; however, when the table is rotated by 90°, weakly bireflectant andorite becomes clearly visible in comparison with gray stibnite in its darkest position. In crossed polars, the difference between weakly anisotropic andorite and
Fig. 11. Sulfosalts of the Vorontsovskoe deposit, part I:
a - aktashite intergrown with Mn-Hg-bearing sphalerite, an unnamed phase I (UK1), and routhierite in calcite; b -andorite and orpiment inclusions in stibnite; c - auerbakhite inclusions in calcite with realgar and pyrite; d - benleonardite, geocronite, and tsnigriite inclusions in galena with quartz; e - large monomineral boscardinite aggregate in calcite; f -boscardinite crystals and grains in calcite (black) in assemblage with realgar, baryte, and pyrite; g - aggregate of écrinsite with christite, dalnegroite, and realgar in calcite; h - aggregate of écrinsite with chabournéite and guettardite in calcite/ dolomite in assemblage with routhierite and stibnite; i - aggregate of boulangerite, heteromorphite, plagionite, semseyite, and galena at the contact of sphalerite with pyrite.
BSE images.
very strongly anisotropic stibnite with bright color effects becomes more pronounced. The composition of the mineral better corresponds to andorite-VI; it contains Cu, Mn, and As in chemical composition (Table 5).
Auerbakhite MnTl2As2S5 is one of eight new mineral species found at the deposit (Kasatkin et al., 2021). Its name honors Alexander Andreevich Auer-bakh (1844-1916), a Russian mining engineer, manufacturer and mineralogist. At the end of the 19th century, his activities were closely related to the Northern Urals. In 1884, he founded the Turyinsk Mining School at the famous Turyinsk Copper Mines. In 1881-1896,
he managed the Bogoslovskiy mining district, developed and improved the copper smelting production of the region. The Auerbakh intrusion and Auerbakh ore district with the Vorontsovskoe gold deposit are also named after him. A.A. Auerbakh is the author of several mineralogical papers published in «Gornyi Zhurnal» («Mining Magazine») and was the first one in Russia, who used microscopic techniques to study minerals.
Samples with auerbakhite were collected directly in the bottom of the northern open pit of the deposit. Auerbakhite occurs in assemblage no. 3 and was found
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Chemical composition (wt. %) of sulfosalts
Table 5
An. no. As. no. Mineral name Mn Fe Cu Zn Ag Hg n Pb As Sb S Total Formula
1 1 - 1.58 25.48 2.76 - 24.29 - - 19.80 0.49 25.45 99.85 CU6.06CHgl.83Zno.64Fe0.43)2.90(AS3.99Sb0.06)4.05Sll.99
2 4 Aktashite - - 23.07 - - 35.13 - - 16.23 2.60 23.50 100.53 Cu6.oiHg2.9o(AS3.59Sbo.35)3.94Sl2.14
3 5 1.02 - 26.19 3.01 25.75 - - 18.30 0.94 25.38 100.59 CUg 25(Hgl.95Zllo 7oMno.28)2.93(As3 70Sbo. 12)3.82S 12.00
4 4 Andorite 0.14 - 1.00 - 11.89 - 0.08 20.88 3.35 38.74 22.85 99.05 Ag0.93Pb0.85CU0.13Mn0.02(Sb2.68AS0.3s)3.0b(S(, ooSCooi )б.01
5 1 Arsiccioite 0.11 0.26 3.09 3.81 5.75 27.78 21.83 - 14.34 2.68 20.19 99.84 (Ago.51 CUo.46)o.97(Hgi .32Zll0.56Fe0.04Mn0.02 )l 94TI1.02 ( AS 1 83 Sbo.21)2.04^6.02
6 3 Auerbakhite 7.34 - - - - 51.89 0.50 18.79 - 20.70 99.22 Mll1.04Tl1.97Pb0.02ASl.95S5.02
7 8 6 7 Benavidesite 1.57 2.64 1.11 - - - - - 40.03 40.24 1.21 35.83 33.60 21.97 22.08 100.51 99.77 Pb395Mno.59Feo.4iSb6.02S14.O3 Pb3.97Mn0.9s(Sb5.64AS0.33)5.97Sl4.08
9 - Benleonardite - - 0.68 - 63.07 - - - 1.12 7.12 8.47 99.50 Agl5.67CUo.29(Sbi.57ASo.4o)l.97Te4.ooS7 OS
10 1 - - - - - - 22.80 - 21.34 29.58 27.08 100.80 Tll.05(AS2.69Sb2.29)4.9sS7.97
11 2 Bernardite - - - - - - 21.40 0.13 25.32 25.39 27.98 100.22 Tl„.96Pb„.„1(AS3.l0Sb,.92)5.02S8.01
12 3 - - - - - 25.55 0.22 42.25 1.31 30.07 99.40 Tll.07Pbo.Ol(AS4.82Sbo.09)4.9lSs.01
13 1 - - - - 2.01 - 12.60 17.82 12.19 30.86 24.22 99.70 Ago.89Tl2.95Pb4.1l(Sbl2.12AS7.78)l9.9oS36.14
14 1 0.14 0.20 0.02 - 1.51 - 12.60 21.32 12.19 29.16 24.52 101.71 Ago.66Feo.l7Mno.i2CUo.oiTl2.92Pb4.87(Sb1133AS7,7o)l9.03S36.19
15 1 0.08 0.25 - - 1.53 - 12.81 20.87 12.22 29.12 24.46 101.33 Ag0.67Fe0.2lMn0.07Tl2.97Pb4.78(Sbll.35AS7.74)19.09836.20
16 1 - - - - 1.66 - 13.53 18.50 13.16 29.41 24.28 100.54 Ago 73TI3 ! 5Pb4.25( Sb 11.49 AS8.36) 19.85S36.O3
17 18 19 20 1 1 1 2 Boscardinite 0.13 0.15 0.14 0.15 0.07 0.05 0.03 0.02 0.02 - 1.51 1.54 1.74 1.49 - 12.71 12.23 12.64 13.23 19.15 21.89 21.77 21.53 13.51 14.38 15.27 15.44 27.06 25.93 25.12 25.13 24.06 25.14 25.1 24.75 98.13 101.34 101.87 101.77 Ag0.6sFe0.13Tl3.0lPb4.47(Sbi0.74AS8.7l)l9.45S36.27 Ago.67Mllo.iiFeo.06Tl2.7oPb4.93(Sb9.93AS8.90l8.88 (S36.56Se0.02)36.58 Ag0.75Mll0.l3Fe0.04CU0.02Tl2.87Pb4.87(Sb9.57 AS.) 45)l9.02 (S36.3oSeo.ol)36.31 Ag0.64Mn0.l2Fe0.03CU0.02Tl3.02Pb4.85(Sb9.64AS9.62)l9.26S36.05
21 5 0.14 - 0.02 - 1.51 - 12.60 21.32 12.19 29.16 24.52 101.46 Ago.66Mno.i2CUo.oiTl2.93Ph|.88(Sbii 37 AS7.72) 19.O9S36.3O
22 23 - Boulangerite - - - - - - - 55.53 54.84 - 25.92 26.02 19.07 18.85 100.52 99.85 Pb49gSb3.96Sn.06 Pb4.96Sb4.00Sn.0iSe0.03
24 - Bournonite - - 13.63 - - - 44.30 6.60 14.78 20.49 99.80 Pb, ooCUl.01Sb0.57AS0.4iS3.00
25 1 - - - - - - 18.47 11.15 13.89 32.97 25.22 101.70 TI7 8lPb4.65Sb23.4i ASi6.03S68.OO
26 2 Chabournéite - - - - - - 17.47 10.96 13.86 32.89 24.85 100.03 Tl7 5oPb4.64Sb23.7oASi6.23S68 00
27 5 0.03 - 0.01 - 0.07 - 18.85 10.31 16.61 29.83 25.46 101.17 Ag0.06Mll0.05CU0.0iTl7.90Pb4.26Sb20.98ASl8.9sS6S.00
28 1 - - - - - 34.5 35.73 - 12.62 - 16.40 99.25 Tll.02Hg1.01AS0.98S2.99
29 1 Christite - - - - - 33.36 35.65 0.28 13.25 0.08 17.03 99.65 Tll.00Hg0.95Pb0.0iAS1.01S3.03
30 4 - - - - 34.64 36.01 - 12.55 - 16.49 99.69 Tll.03Hg1.01AS0.98S2.99
31 5 Clerite 13.77 - - - - - - 4.64 51.91 30.87 101.19 Mni.o3(Sbi.75ASo.25)2.0oS3.96
32 - Cupropolybasite - - 18.05 54.04 - - - 11.59 17.01 100.69 Ag9.ooCUl.oo(CU4.84Agi.3o)6.14Sbl.96Sln9l
33 1 - - - - 0.12 2.22 20.14 10.95 26.58 14.80 26.12 100.93 Ag0.05Hg0.46Tl4.06Pb2.l8AS14.63Sb5.0iS33.6l
34 35 1 1 Dalnegroite 0.02 0.04 0.20 0.20 0.10 0.19 0.03 19.53 18.25 10.39 11.79 23.13 17.63 21.08 28.25 26.36 25.27 100.59 101.89 Ag0.04Tl3.95Pb2.74AS12.77Sb7.l6S34.0i CU0.14Zll0.13Ag0.08Fe0.03Mn0.02Tl3.s0Pb2.42AS10.00Sb9.87S33.52
36 2 0.03 - - - 0.07 - 18.85 10.31 17.61 27.83 25.96 100.66 Ago.O3Mnoo3Tl3.91Pb2.llAS9.95Sb9.68S34.29
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An. no. As. no. Mineral name Mn Fe Cu Zn Ag Hg T1 Pb As Sb S Total Formula
37 2 Dalnegroite - - - - - - 19.20 9.99 21.04 23.43 25.82 99.48 Tl3.97Pb2.04Asn.86Sbs.13S34.01
38 3 Dalnegroite? 0.30 - - - - - 24.38 0.27 22.34 25.24 26.98 99.51 Mno.2iTl4.87Pbo.07AS12.i4Sb8.43S34.28
39 3 («protodalnegroite») 0.07 - 0.02 - - - 20.78 7.71 19.53 26.47 26.19 100.77 Mn0.05CU0.01Tl4.25Pb1.56AS10.90Sb9.09S34.i5
40 1 Dewitite - - - - - - 23.10 0.25 16.08 35.12 26.30 100.85 Tl9.37Pb0.10Sb23.91As17.79S68.00
41 1 Drechslerite - - - - - - 53.46 - 5.17 24.73 16.80 100.19 Tl3.96(Sb3.07ASl.04)S7.93
42 1 - - - - - - 54.67 - 7.24 20.62 17.09 99.62 Tl4.0l(Sb2.54ASl.45)Ss.00
43 - Dufrénoysite - - - - - - - 55.98 15.43 6.87 21.37 99.65 Pb2.03(ASi.55Sb0 41)1.9785.00
44 1 - 0.23 - - 1.64 - 14.17 16.50 16.50 26.06 24.67 99.77 Ago.7lFeo,19Tl3 2зРЬз 71 (ASio.27Sb9 99)20.20835.89
45 1 Écrinsite - 0.25 - - 1.55 - 8.72 26.04 17.84 20.78 24.28 99.62 Ago. 6sFeo.2iTl2.oiPb5 93 (As 1124 Sbs.oö) 19.30(835.76 Seo. 10)35.86
46 2 0.30 - - - 1.21 - 8.41 30.71 15.74 19.92 24.77 101.06 Ago.53Mno.26Tll.95Pb7.0l(AS9.94Sb7.74)l7.68S36.56
47 5 - - - - 0.18 0.27 13.77 20.03 19.83 20.70 25.79 100.57 Ago.osHgo 0бТ1з 0?РЬ4 40(AS 12.05 Sb? 74)19 79S36.61
48 2 Enneasartorite - - - - - - 6.69 35.05 18.94 14.83 24.08 99.59 Tl6.1lPb3i.60(AS47.22Sb22.75)69.97Sl40.31
49 2 Ferrovorontsovite - 9.89 3.95 1.16 0.45 25.13 12.93 0.04 17.83 2.15 24.91 99.28 [(Fe 2.74Hgi 94Zllo 27)4.95(CUo.96 Ago 06)1.02] (Tlo.9sCSo.05) 1.03 (AS3.68Sb0.27Te0.05)4.00Sl2.00
50 2 Galkhaite - 2.47 3.25 0.91 - 45.20 5.05 - 15.96 1.24 21.58 100.43 [(H§4.0lFeo.79Zrio.25)s5.05CUo.9l]5.96(CSo.64Tlo.44)l.08(AS3.79 Sbo. 13)3.978 и 99
51 - Geocronite - - - - - - - 67.58 4.37 9.80 17.23 98.98 Pbl3.99(Sb3 45AS2.50)5.95823.05
52 3 Gillulyite - - - - - - 29.49 0.19 40.02 1.73 29.52 100.95 Tl2.04Pbo.Ol(AS7 54Sbo.21)7.75S 13.00
53 3 Sb-gillulyite? 0.12 - - - - - 24.54 1.27 21.47 26.95 26.73 101.08 Tll 8бРЬо.10-^1По оз(А84 448Ьз 43)7 87812.93
54 3 Gladkovskyite 8.28 - - - - - 30.04 0.23 31.80 2.27 28.58 101.20 МП] 01Tl0.99Pb0.0iAS2.86Sb0.13S6.00
55 1 - - - - - - 5.14 33.25 13.66 22.30 24.17 98.52 Pty) 86^0 13^S0 98^0 98^4 04
56 57 2 4 Guettardite - 0.01 - - 0.05 - 2.45 0.15 37.42 39.82 15.82 15.73 20.06 21.42 24.60 24.49 100.35 101.67 Pbo.95Tl0.06ASl.11^0.86^4.02 Pbl.00AS109Sb0.92S3.98
58 2 Gungerite - - - - - - 13.68 - 26.77 30.97 28.02 99.44 Tlo.99AS5.29Sb3.77S12.95
59 2 Heptasartorite - - - - - - 9.51 31.38 19.21 15.35 23.93 99.38 Т1б.7зРЬ21.9 l(AS37 Ю Sb 18.24)55.34 S 108.01
60 61 - Heteromorphite - - - - - - - 48.69 49.37 0.42 0.25 30.85 30.59 19.65 19.95 99.76 100.28 Pb7.2iSb7.77ASo.i7Sl8.79Seo.O6 Pb7.25 Sb7.65AS0.10Sl8.95 Se0.05
62 63 1 2 Hutchinsonite - 0.10 0.01 0.03 - - 18.09 18.84 18.15 18.51 29.79 30.05 6.40 5.52 25.74 25.93 98.31 98.85 Feo.02Zrio.oiTlo.99Pbo.98(AS4.44Sbo.59)5.03S8.97 Tll.03Pbo.99(AS4.47Sbo.5o)4.97S9.oi
64 3 - - - - - - 19.14 18.68 31.25 4.73 26.54 100.34 Tll.02Pbo.98(AS4.55Sbo.42)4.97S9.03
65 3 Imhofite - - - - - - 36.30 - 30.02 8.43 25.37 100.12 Tl5.83(ASl3.l4Sb2.27)l5.4lS25.96
66 67 6 Jamesonite 0.53 1.97 2.59 - - - - - 40.47 40.18 - 34.74 35.18 21.56 21.80 99.27 99.75 Pb4.08Fe0.74Mn0.20Sb5.95S14.03 Pb4.0iFe0.96Sb5.97S14.06
68 7 Jordanite - - - - - - - 69.05 6.90 5.89 17.55 99.39 Pbl4.03(AS3.88Sb2.04)5.92S23.05
69 4 Laffittite - - - - 23.10 40.90 - - 15.95 - 20.16 100.11 Agl.02Hg0.97AS! .01 S2.99
70 8 Lillianite - - 0.22 - 6.54 - - 27.72 - - 16.80 101.39 Pbl .52Ago 69CUo 04^12.67(85 95 Seo. 13)б.08
71 3 Lorándite - - - - - - 58.49 0.42 20.57 0.45 19.37 99.30 Tlo.98Pbo.Ol(ASo.94Sbo.o 1)0.9582.06
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72 5 Luborzákite 21.23 - 0.29 - 0.56 - - 1.90 15.25 27.03 33.23 99.49 Mn1.8sPb0.04Ag0.03Cu0.02AS0.9sSb1.07S5.00
73 5 Pb-luborzákite? 16.14 - 0.07 - - 0.05 0.09 9.01 9.20 34.15 29.99 98.70 Mn1.5sPb0.23Cu0.01AS0.ssSb1.50S5.02
74 1 Maiigaœquadratite 17.84 - - - 30.73 - - - 21.78 - 30.06 100.41 Ago.93Mni 06 ASo.95 S3.06
75 - Meneghinite - - 1.45 - - - - 61.31 - 19.4 17.55 99.71 Pb12.98CUl.00Sb6.99S24.02
76 4 Nowackiite - 2.03 27.34 6.09 - 15.62 - - 20.66 1.73 27.72 101.19 CU6.oo(Zni 30Hgi o9Feo.5l)2.9o(AS3.85Sbo.2o)4 05^12.06
77 1 Oyonite 3.09 0.03 0.15 - 10.62 0.25 0.17 24.64 8.77 28.57 24.49 100.78 Mn1.7sFe0.02Ag, ,, CU0 07Hg0.04Pb3.75Tl0.03Sb7.41 AS, 69S24.ll
78 4 - - - - - - 19.49 - 2.02 54.78 24.14 100.43 Til 0l(Sb4 75 ASo.28)5.03 S7 95
79 4 - - - - - - 19.01 0.31 2.4 54.91 24.34 101.00 Tl0.97Pbo.02(Sb4.72ASo.33)5.05S7.95
80 4 - - - - - - 19.20 0.26 2.77 54.10 24.39 100.82 Tlo.98Pbo.Ol(Sb4.65ASo.39)5.04S7.96Seo.01
81 4 - - - - - - 19.75 0.55 3.49 53.77 24.64 102.29 Tll.ooPbo.03(Sb4.57ASo.48)5.05S7.9oSeo.ol
82 4 - - - - - - 19.02 0.35 3.73 52.63 24.09 99.82 Tl0.9sPbo.02(Sb4.55ASo.53)5.08S7.92
83 84 4 4 Parapierrotite 0.06 — 0.04 — 0.08 — 20.1 20.56 0.27 8.61 11.90 46.08 41.43 25.17 24.65 99.96 98.99 Til.oo(Sb3.85ASl. 17)5.0287.98 Tli. 03Pbo.oiMno.oiCUo.oiAgo.oi(Sb3.47ASi. 62)5.0987.84
85 4 - - - - - - 22.69 - 15.32 35.46 25.75 99.22 Til lo(Sb2.89AS2.03)4.9287.98
86 2 - - - - - - 20.32 - 15.70 38.09 26.84 100.95 Tlo.95(Sb3.ooAS2.0l)5.01 Ss.03
87 4 - - - - - - 23.05 0.91 16.51 32.89 26.03 99.39 Til. nPbo.04(Sb2.66AS2.17)4.8388.01
88 5 1.36 - - - - - 22.4 - 17.09 32.68 26.78 100.31 Tli .О5МП0.24Sb2.56AS2.lsS7.98
89 5 1.59 - - - - - 22.58 - 17.55 31.70 26.82 100.24 Til .O5Mno.28Sb2.48AS2.23 S7.96
90 8 Pavonite - - 0.31 - 11.12 - - 2.68 - - 18.20 99.10 ( Ago 92CUo o4)o.96(BÍ2.82Pbo. 11 Teo.01)2.94(85.05860.05)5.10
91 3 Philrothite - - - - - - 33.17 0.59 34.40 3.94 27.06 99.16 Tlo.97Pbo.02(AS2.75Sbo. 19)2.9485.06
92 - Plagionite - - - - - - - 40.53 - 38.58 21.48 100.88 Pb4.95Bi0.02Sb8.02Sl6.96Se0.04
93 1 Pokhodyashinite - - 4.59 - 3.79 - 27.88 0.42 7.63 32.95 21.89 99.15 Cu„ vnAgn ,1T11 „Pbn mSb, fi,Asn 008й
94 - Polybasite - - 9.05 - 64.60 - - - - 10.75 16.10 100.50 Ag0„„CUi.oo(Ag4.o4CU2.lo)6.14Sbi.92Sio.94
95 6 Ramdohrite 2.36 0.74 2.27 0.32 5.75 - 0.80 33.61 2.16 29.91 22.15 100.07 Agl.83Mni.47CU1.23Fe0.45Zn0.17T10.13Pb5.57(SbS.43AS0.99)9.42 S22.03
96 1 - - - - - - 34.80 0.36 22.98 16.82 24.23 99.19 TI4 96Pbo.05(AS8.94Sb4 03)12.97822 02
97 1 Rebulite - - - - - - 36.04 - 20.32 18.89 25.13 100.38 TI5 09(AS7 82Sb4 48) 12 30S22.6I
98 3 - - - - - - 36.10 0.29 30.63 7.08 25.34 99.44 Tl4 9iPbo.04(ASn 398b 1 62)13.01 S22.03
99 100 4 4 Roshchinite 0.16 0.15 0.02 0.02 0.02 _ 15.7 15.02 2.72 2.98 0.10 0.13 14.16 14.32 11.43 10.69 30.59 31.05 25.07 25.06 99.95 99.44 Agl7.42Hgl.86^.344.04^0.04Pb8.65T10.08(Sb31.91ÄS17.85)49.76 S978O
101 1 0.11 0.08 3.93 3.76 4.70 27.42 21.74 0.17 14.17 2.65 20.28 99.01 (CU0.59Ag0.42)l.0l(Hgi.3lZn0.55Mn0.02Fe0.0l)l.89Tll.02Pb0.01 (ASi 81 Sbo.21)2.0286.05
102 2 Routhierite - - 5.92 0.51 0.25 38.87 19.21 - 13.97 1.72 19.03 99.48 (CUo 94Ago 02)0.9ö(Hgi 96Zno 08)2.04Tlo.95(ASi 89Sbo. 14)2.0386.01
103 5 - - 5.98 1.02 0.63 36.52 20.95 0.09 14.52 1.30 18.60 99.61 (CUo.95 Ago.o6)l .01 (Hgi 84ZII0. löb.OoTll .04?Ь0.01 (ASi 9öSbo 11)2.07 S5.87
104 - Semseyite - - - - - - - 52.78 - 27.92 19.08 99.93 Pb8.95Sb8.06S20.92Se0 07
105 1 Sicherite - 0.10 - - 23.83 - 22.63 0.22 16.71 13.69 21.61 98.79 Tlo.99Pbo.Ol(Agi.97Feo.02)si.99(ASl.99Sbl.oo)s2.99S6.02
106 1 Sinnerite - - 38.58 - 0.10 - - - 29.74 0.27 28.71 97.40 CU6.06Ago.oi(AS3.96Sbo.02)3.98S8.94
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An. no. As. no. Minerai name Mn Fe Cu Zn Ag Hg T1 Pb As Sb S Total Formula
107 1 Stalderite 0.10 - 4.07 8.16 4.92 20.49 22.24 - 15.02 2.50 21.29 98.79 (CUo^sAgo^Oo^Zn! .12Hgo.92Mno.o2)2.06Tlo.98(ASi.81 Sbo is)l 99S5 98
108 1 «Tennantite-iMnï» 2.70 1.82 36.08 0.12 5.79 6.87 - - 16.70 3.09 26.01 99.18 (CU9.i5Ago.87Mno.79Hg)55Feo.53Zno.o3)ll.92(AS3.59Sbo.4l)4.ooSl3.08
109 4 Tennantite-(Zn) 0.01 1.47 39.10 6.35 3.23 0.41 0.04 0.10 13.81 8.53 26.49 99.54 (CU9.65Ago.47Zni.52Feo.4lHg).o3Pbo.ol)l2.09(AS2.9oSbl.lo)4.0oSl2.97
110 - «Tetrahedrite-(Mn)» 3.20 2.62 38.80 0.17 0.07 - - - 3.25 25.68 26.01 99.80 (CU9.6lAgo.oiMno.92Feo.74Z n<).04)ll.32(Sb3.32ASo.68)4.0oS 12.77
111 - Tsnigriite - - - - 62.02 - - - - 7.32 5.94 100.09 Ag9.07Sb0.95Te3.07S2.92
112 7 Tsygankoite 6.29 - - - - 5.42 26.05 5.84 3.39 30.89 21.87 99.75 Mll8.o6Tl8.0oHgl.9o(Sbi7.87AS, ,qPbi99^0.97)24.02848.03
113 114 1 5 Twinnite - - - - - - 2.80 2.95 33.43 34.02 12.23 10.40 26.63 27.77 23.58 24.41 98.67 99.55 Pbo.87Tlo.07(Sbl.l8ASo.88)2.06S3.98 Pbo.88Tlo.08^Sb 1.22ASq 74)1.9684.08
115 7 Veenite - - - - - - 6.77 45.99 8.72 18.39 21.32 101.19 Pb 1 6sTlo.25( Sb 1.14 ASo. 88)2.0285.04
116 - Vikingite - - 0.58 - 6.07 - - 28.84 - - 17.01 99.23 Ag3.28Cllo.53Pb8.13Bii3.o3S,097Seo.05
117 2 Vorontsovite - 5.36 3.42 1.26 0.64 35.70 11.53 0.04 15.98 2.35 22.70 99.76 [(Hg3.02Fei 63Zllo 33)4 9s(CUo 91 Ago 10)1.01] (TI0 96CS0.04) 1.00 (AS3.62Sbo.33Teo.05)4.0oS 12.01
118 119 1 3 Vrbaite - 0.17 - - - 19.72 20.42 27.67 28.52 0.24 20.20 20.61 8.54 8.57 22.00 22.32 98.54 100.44 Hg2.88Fe0.09Tl3.96Pb0.03AS7.89Sb2.05S20.09 Hg2.94Tl4.02AS7.93Sb2.03S20.08
120 121 1 1 Weissbergite - - - - - - 51.12 53.31 0.69 0.47 3.42 31.08 27.81 16.53 16.61 99.89 101.15 Tlo.97Pbo.Ol(Sbo.99ASo.02)l.OlS2.00 Tlo.99(Sbo.87ASo. 17)1.04S1.97
122 123 124 1 Zinkenite - - - - - - - 31.87 32.91 32.02 7.55 4.28 45.03 35.07 40.37 22.64 23.90 23.42 99.54 99.43 100.09 Pb9.i3Sb2i.95S41.92 Pbs.97(Sbi6.26AS5 69)21.95842.08 Pbs.86(Sbl9 0oAS3 27)22.2784] S7
125 1 UK phase I 2.38 - - - 2.53 0.47 10.52 24.48 17.98 16.76 24.96 100.08 Mni 99Agi 08Hg0.11Tl2.36Pb5.42Asn.01Sb6.32S35.72
126 1 UK phase II 3.29 0.30 0.50 - 12.26 0.58 0.11 15.46 8.58 32.83 25.47 99.38 Mn0.91Agl.73cu0.12Fe0.08Hg0.04T10.01pbl.14sb4.ll AS1.75S12.11
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Note. The analytical total includes (wt.%): an. 4-0.12 Se; an. 9 - 19.04 Te, an. 23 - 0.14 Se; an. 45 - 0.16 Se; an. 50 - 4.77 Cs; an. 59 - 0.15 Se; an. 60 - 0.12 Se; an. 70 - 49.20 Bi, 0.91 Se; an. 80-0.09 Se; an. 81-0.10 Se; an. 90 - 66.21 Bi, 0.10 Te, 0.48 Se; an. 92-0.12 Se, 0.17Bi; an. 104-0.15 Se; an. 49 - 0.40 Te, 0.44 Cs; an. 111 - 24.81 Te; an. 116 - 0.07 Se, 46.66 Bi; an. 117 - 0.02 Se, 0.41 Te, 0.35 Cs. The low analytical total of an. 106 is due to subtraction of pyrite from the matrix. Analysis 110 was taken from (Murzin et al., 2011). Dash - the content of element is below détection limit.
Samples: Vor-8-2 - an. 1, 41; Vor-10-8 - an. 2; Vor-19-01emf- an. 3, 27; SK-18-19 - an. 4, 109; Vor-10/2017-2 - an. 5, 35, 107; VK-27-3 - an. 6, 91; Vor-08-18-13 - an. 7, 66; Vor-10-6 - an. 8, 68; Vor-08/20-20 - an. 9, 51, 111; Vor-8-3 - an. 10; Vor-03/16-6-3 - an. 11, 102; VK-27-4 - an. 12, 53, 54; Vor-10/2017-2b - an. 13, 18, 19; Vor-10/2017-2v - an. 14; Vor-10/2017-2d - an. 15, 17, 44, 105; Vor-01/19-16 - an. 16, 106; Vor-08/20-7 - an. 20, 46, 50; Vor-19-05emf - an. 21; 905B - an. 22; Vor-08/20-22 - an. 23, 60, 61, 92, 104; Vor-08/20-14 - an. 24; Vor-10bis-3c - an. 115; Vor-10/2017-1 - an. 93, 101, 120; Vor-08/20-26 - an. 116; Vor-
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in limestone breccias composed of calcite, dolomite, baryte, clinochlore, fluorapatite, and quartz, which are enclosed in realgar, orpiment, and pyrite. Auerbakhite is associated with alabandite, bernardite, christite, cinnabar, coloradoite, dalnegroite, gillulyite, native gold, hutchinsonite, imhofite, lorandite, metacinnabar, phil-rothite, rebulite, routhierite, sphalerite, and vrbaite. Auerbakhite forms rare small short-prismatic crystals and irregular grains measuring maximum 15 x 5 pm in size (or even smaller) (Fig. 11c). Auerbakhite is transparent and has a bright red color and an adamantine luster. It is brittle, with an uneven fracture. No cleavage was observed. The calculated density is 5.245 g/cm3. In reflected light, auerbakhite is light gray, weakly bi-reflectant. It is distinctly anisotropic in light gray and brown tones. The mineral exhibits abundant bright red internal reflections. In transmitted light, auerbakhite is moderately pleochroic from orange-red to dark red. The reflectance spectra are shown in Fig. 12. The reflectance values for the wavelengths recommended by the Commission on Ore Mineralogy of the IMA are (RmJRmax, %): 25.2/27.1 (470 nm), 24.0/25.2 (546 nm), 237/247 (589 nm), 23.0/24.0 (650 nm). The chemical composition of the holotype sample is shown in Table 5. Its empirical formula (based on the atom sum of 10) is Mnt 04Tlj 97Pb002Asj 95S502. Auerbakhite is or-thorhombic, space group Cmce, Z = 8. The unit cell parameters are given in Table 3.
In the Raman spectrum of auerbakhite (Fig. 13a), the most high-force-strength bonds are Mn-S. Bands of M-S stretching vibrations in the Raman spectra of pyrite-type compounds MS2 (M = Mn, Co, Ni, Cu, Zn) with 3D systems of vertice-sharing MS6 octahedra are observed in a range of 380-500 cm-1 (Anastassakis, Perry, 1976). Slightly lower frequencies should be expected for auerbakhite, which contains 1D system of MnS6 octahedra. This conclusion is in agreement with the positions of the strong high-frequency bands observed in a range of 350-400 cm-1. By analogy with the Raman spectra of orpiment and realgar (Forneris, 1969; Minceva-Sukarova et al., 2003), the bands in a range of 300-350 cm-1 are assigned to As-S stretching vibrations. The assignment of the Raman bands with wavenumbers below 260 cm-1 is ambiguous. These bands possibly correspond to mixed soft modes involving bending vibrations, as well as Tl-S stretching vibrations.
The crystal structure of auerbakhite (Fig. 14) is identical to the structure of a synthetic phase Tl2Mn As2S5 (Gostojic et al., 1982). It consists of complex (001) layers based on a set of MnS4 columns, which
Fig. 12. Reflectance spectra of new sulfosalts from the Vorontsovskoe deposit.
are parallel to [010] and are composed of edge-sharing modestly irregular MnS6 octahedra. The columns are framed by paired AsS3 pyramids with lone electron pairs oriented into interlayer space. Highly irregular Tl2S6 coordination polyhedra are situated in the inter-layers and share ligands with the layers. Til is part of the complex (001) layer, however, interconnecting the Mn octahedral rods within this particular layer.
Benavidesite Pb.MnSb,S, .was found for the first
4 6 14
time in assemblage no. 7 (Kasatkin et al., 2018b) as in-tergrowths with sphalerite up to 20 pm in size in calcite with clinochlore. In assemblage no. 6, it forms rounded grains up to 40 pm in size in a vesuvianite-diopside rock. In reflected light, benavidesite is white with a faint greenish tint; bireflectance is distinct in air and strong in immersion. In crossed-polarized light, the mineral is strongly anisotropic in brownish tones. The chemical composition varies depending on the assemblage: in assemblages no. 6 and 7, benavidesite contains significant contents of Fe, which isomorphically substitutes for Mn, and low amount of As, which is isomorphic with Sb, respectively (Table 5). Our finding is probably the first in the Russian Federation.
Jamesonite Pb4FeSb6S14, a Fe analog of benavidesite, is more common at the deposit. It was first identified by XRD in a sample with boulangerite and bournonite (Sazonov et al., 1991a). Later, jamesonite was found as inclusions <0.5 mm in size in gangue minerals of the breccia matrix, where it intergrows with boulangerite, zinkenite, chalcostibite and stibnite (Vikentyev et al., 2016). In our sample,jamesonite was found in assemblage no. 6, where it occurs as inter-growths with tetrahedrite-(Zn) up to 50 pm in size in
carbonates with vesuvianite and diopside. It was also identified in samples from off-balance ore stockpile no. 2 as inclusions up to 0.1 mm in size in pyrite, sphalerite, and carbonates (dolomite, calcite). The optical properties of jamesonite and benavidesite are identical. Jamesonite from assemblage no. 6 contains some amount of Mn in contrast to Mn-free jamesonite from off-balance ore stockpile no. 2 (Table 5).
Benleonardite Ag15Cu(Sb,As)2S7Te4 was found by V.V. Murzin (Mineralogy..., 1991) at the western flank of the deposit in a mineralization zone, which is composed of epidote-actinolite-chlorite-carbonate metasomatites with disseminated galena, sphalerite, chalcopyrite, and pyrrhotite. Together with pyrargyr-ite, benleonardite forms lamellar aggregates up to 0.06 mm in size along the cleavage planes in galena. The mineral was identified by its chemical composition and optical properties. In comparison with the theoretical composition, benleonardite from the Vorontsovskoe deposit is characterized by an almost complete absence of Cu. Recently, Bindi et al. (2015) refined the structure of benleonardite and considered it as a member of the pearceite-polybasite group with Cu as an essential element in its structure. Benleonardite from different localities, including the type material from the Bambolla Mine, Mexico, however, is depleted in Cu or even Cu-free (Stanley et al., 1986; Bindi et al., 2015), similarly to our mineral from Vorontsovskoe deposit.
In our samples, benleonardite was found in cal-cite-dolomite-quartz aggregates with galena and sphalerite in samples from off-balance ore stockpile no.2. Benleonardite forms small (up to 20 pm in size) inclusions in galena and is associated with geocronite,
Fig. 13. Raman spectra of sulfosalts from the Vorontsovskoe deposit:
a - auerbakhite; b - gillulyite; c - gladkovskyite; d - gungerite; e - lorandite; f - rebulite; g - hutchinsonite. Intensity and wavenumbers (cm-1) are shown vertically and horizontally, respectively. The measured spectrum is shown by dots. The black curve matching the dots is a result of spectral fit as a sum of individual Voigt peaks (orange).
Fig. 14. The crystal structure of auerbakhite projected along [010].
Axis c axis is horizontal. Columns of Mn-coordinated octahedra (perpendicular to the projectionplane; red spheres) are alternated with Tl1 polyhedra (large mauve spheres) in layers parallel to plane (001). The T12 coordination polyhedra (large mauve spheres) are located in interlayers. The As and S atoms of AsS3 pyramids are shown as orange and lemon yellow spheres, respectively
hessite, and tsnigriite (Fig. lid). The mineral is also characterized by a deficit of Cu (Table 5). The reflectance of benleonardite is moderate: in reflected light, it looks light gray in comparison with the host white galena, whereas the mineral exhibits distinct anisotropy in brownish and bluish tones.
Bernardite TlAs5S8 was found for the first time in the Russian Federation in assemblages nos. 1-4 as rare small (up to 50 pm in size) anhedral grains in gangue minerals of breccias (calcite, baryte, clino-chlore) and single intergrowths with parapierrotite and vorontsovite. In reflected light, bernardite is light gray; its bireflectance is weak. The effects of anisotropy are very strong in white and brownish tones; the internal reflections are orange-red. The chemical composition of the mineral is heterogeneous: the Sb contents ranges from 1.3 wt. % in assemblage no. 3 to 29.6 wt. % in assemblage no. 1 (Table 5). The monoclinic unit cell parameters of most stoichiometric bernardite from assemblage no. 3 are given in Table 3.
Bernarlottiite Pb6(As5Sb3)S18 of a problematic chemical composition was indicated in the gold-pyrite-realgar assemblage as a mineral intergrowing with sphalerite and enclosing enargite (Vikentyev et al., 2016).
Boscardinite and its As-dominant isostructural
analogue ecrinsite were found for the first time in the Russian Federation in assemblages nos. 1, 2, and 5.
Boscardinite was initially described at the Monte Ar-siccio Mine (Tuscany, Italy) as a new mineral with formula TlPb4(Sb7As2)9S18 (Orlandi et al., 2012). Further structural studies of new material from the same locality (Biagioni, Moelo, 2017) revealed a widely variable chemical composition of the mineral up to AgTl3Pb4(Sb14As6)20S36 and different occupancy of ten structural sites by Sb and As. In particular, in holo-type As was dominant only in one site in contrast to three dominated positions in new material. Despite these chemical and structural differences (including different contents and distribution of Pb and T1 in structural sites), it was the same mineral, boscardinite, with a species-defining feature of Sbtot>Astot (Biagioni, Moelo, 2017). Ecrinsite with the formula AgTl3 Pb4As11Sb9S36, an As-dominant isostructural analog of boscardinite, was described at the French Jas Roux deposit in the same year (Topa et al., 2017a).
At the Vorontsovskoe deposit, boscardinite and ecrinsite show a very broad Sb ^ As substitution. In assemblage no. 1, they form a solid solution series ranging from Bsc74Ecr26 to Bsc17Ecr83 with a gap in the ecrinsite field from Bsc18Ecr82 to Bsc39Ecr61 (Fig. 15). Both minerals occur as small anhedral grains (less than 50 pm in size, with some individuals up to 0.2 mm in size) in carbonates and quartz, rims around pyrite grains and aggregates with realgar and various Tl sul-fosalts (christite, dalnegroite) (Figs, lle-llg). In one sample with assemblage no. 1, ecrinsite forms a complex 0.3 mm intergrowth with chabourneite, guettar-dite, and stibnite (Fig. llh). In assemblages nos. 2 and 5, boscardinite and ecrinsite are less common and form aggregates up to 50 pm in size enclosed in Mn-bearing carbonates and realgar and, in assemblage no. 5, they are intergrown with luborzakite and realgar (Fig. 21b). In reflected light, both minerals are white and look light gray at the contact with pyrite that is in agreement with the original data on their reflectance values: at X = 546 nm R = 32.1-38.0 % for boscardinite (Orlandi et al., 2012) and 35.2-36.7 % for ecrinsite (Topa et al., 2017a). Bireflectance is noticeable only in boscardinite (only in most Sb-rich grains). Both minerals are distinctly anisotropic in various tints of gray. No internal reflections are observed. The chemical composition of boscardinite and ecrinsite from different assemblages is given in Table 5. Strong reflections of the PXRD pattern of boscardinite are [d, A (/)]: 3.74(40), 3.55(50), 3.46(40), 2.98(40), 2.81(100), 2.71(90), 2.32(50), 2.18(40). The parameters of the triclinic unit cell of both minerals (SXRD data for ecrinsite) are given in Table 3.
Boulangerite Pb5Sb4S11 was described as acicular crystals up to 1 mm long dispersed in carbonates of breccias or as aggregates up to 1 cm across (Sazonov et al., 1991a; Vikentyev et al., 2016). It is closely associated with bournonite, jamesonite, and fahlores. The mineral was determined by chemical composition and optical properties. One analysis of As-boulangerite exhibits 3.05 wt. % As, thus, the empirical formula of the mineral Pb5 07Bi01Sb294As076Se007S1104 formally corresponds to the homeotype of boulangerite, lopatkaite Pb5Sb3AsS11 (Topa et al., 2013). The presence of the latter at the Vorontsovskoe deposit, however, still requires confirmation by XRD studies.
In samples from the dumps of the northern open pit, boulangerite occurs as lead gray hairy and acicular crystals up to 2 cm long in cavities of calcite-dolomite breccias in assemblage with tiny arsenopyrite and chal-copyrite crystals (Fig. 16a). Boulangerite was identified by chemical composition (Table 5) and SXRD data (Table 3). This sulfosalt was also found in an aggregate of sulfantimonites and galena in a sample from the off-balance ore stockpile no. 2. The mineral forms veinlets up to 0.5 mm at the contact with sphalerite and pyrite and aggregates with galena, heteromorphite, and plagionite (Fig. lli). Ithas low Se contents (Table 5).
Bournonite PbCuSbS3 was described as anhedral grains or acicular crystals up to 1 mm long in gangue minerals of breccias often intergrown with boulanger-ite and hosting small andorite inclusions (Sazonov et al., 1991a; Vikentyev et al., 2016). The mineral was identified by chemical composition and optical properties. In our samples, bournonite was found as rare inclusions in native arsenic and lead gray grains up to 5 mm in size in calcite-dolomite marble in assemblage with galena, pyrite, and tetrahedrite-(Zn). Bournonite is enriched in As (up to 6.6 wt. %; 0.41 apfu) (Table 5). The identification of bournonite was confirmed by SXRD data (Table 3).
Chabourneite Tl4Pb2(Sb,As)20S34, recently redefined by CNMNC IMA (Miyawaki et al., 2021), and its As-dominant isostructural analogue dalnegroite Tl4Pb2(As,Sb)20S34 often occur in four assemblages. The size of their grains is typically <0.1 mm. Both minerals form anhedral grains and, rarely, short-prismatic crystals up to 50 pm in size dispersed in ore matrix of breccias (Figs. 17a, 26d, 26k). They are associated with boscardinite-ecrinsite, christite, cinnabar, guet-tardite, parapierrotite, realgar, and routhierite and form inclusions in these minerals (Figs, llg, llh) or epitaxial overgrowths on stibnite. Both minerals are opaque, have black color and metallic luster. In reflected light,
Fig. 15. Sb-As correlation in boscardinite (1) and
ecrinsite (2).
they are white, but dalnegroite has slightly higher reflectance values. The bireflectance of both minerals is distinct. In crossed-polarized light, these sulfosalts are strongly anisotropic in brownish and bluish gray tones, with red internal reflections, which are especially distinct in immersion.
The chemical composition of chabourneite and dalnegroite is given in Table 5. The parameters of the triclinic cell of chabourneite according to SXRD data are given in Table 3. The strongest reflections of the PXRD pattern of dalnegroite from assemblage no. 1 are [d, A (/)]: 3.918(100), 3.774(50), 3.614(50), 3.128(50), 2.932(40), 2.869(60), 2.572(30), 2.101(60). The calculated parameters of its triclinic unit cell are shown in Table 3 No 34. In assemblage no. 2, dalnegroite and chabourneite form an extended series of solid solutions (data of 61 analysis), they often transit into each other even within the same grain. This series extends from Dln63Chb37 to Dln26Chb74 with two gaps in Dln27Chb73-
Dln_Xhb and
33 67
Dln43Chb57-Dln46Chb54 ranges
(Fig. 18).
Our finding of dalnegroite is the first at the territory of the Russian Federation. As for chabourneite, it was first mentioned by Murzin and Varlamov (2010) among Tl sulfosalts included in carbonate breccias of the deposit. The mineral was conditionally ascribed to chabourneite based on chemical analysis. Later, chabourneite was described as anhedral grains up to 0.5 mm in size together with other T1 sulfosalts in late hydrothermal parageneses of carbonate breccias (Vikentyev et al., 2016). The T1 minerals are associated with aktashite, sphalerite, and baryte.
In one sample of assemblage no.l, large (up to 0.4 * 0.1 mm in size) prismatic crystals and grains of a cha-
Fig. 16. Sulfosalts of the Vorontsovskoe deposit, part II:
a - lead gray hairy boulangerite crystals in the cavity of calcite-dolomite breccia; b - dark cherry red prismatic gladkovskyite crystals in carbonate aggregates with orange realgar; c - bright orange gungerite aggregates on carbonate breccia covered by a black greigite film ; d - bright orange gungerite in calcite and dolomite; e - lead gray meneghinite in calcite with pyrite; f - dark red routhierite aggregates in dolomite-calcite matrix; g - elongated lath-like tsygankoite crystals in white dolomite/calcite with veinlets of orange orpiment/realgar and pyrite; h - black vorontsovite-ferrovorontsovite grains in calcite and dolomite with red cinnabar; i - lead gray acicular zinkenite crystals in calcite.
Collection of A.V. Kasatkin. Photo: T.V Pashko (a), A.V. Kasatkin (b, d, g, h), A.D. Kasatkina (c, e, f), M.D. Milshina (i).
bourneite-like mineral were found in calcite associated with quartz, realgar (Fig. 17b), aktashite, coloradoite, native gold, orpiment, parapierrotite, pyrite, routhierite, stibnite, baryte, and prehnite. A specific feature of this mineral is the lack of Pb in chemical composition and higher T1 and Sb contents. Despite that 2Pb2+ ^ Tl+ + Sb3+ substitution is typical of chabourneite, a Pb-free variety was described only once at the Jas Roux deposit in France without structural studies (Johan et al., 1981) in contrast to Pb-rich chabourneite (Biagioni et al., 2015). The crystal structure of the Pb-free end-member of the homeotypic chabourneite family was first solved by us using crystals from the above sample (Makovicky et al., 2021). Soon after our paper was published, the CNMNC IMA approved the chabourne-
ite group (Miyawaki et al., 2021), where chabournéite sensu stricto was redefined as a Pb-rich mineral with the formula AgzTl8_x_zPb4+2xSb40_x_yAsyS68 (with 0.00 < x <0.40, 16.15 <y< 19.11, 0.04 <z< 0.11), whereas our «Pb-free end-member of the chabournéite homeotypic family» became identical to the new mineral dewitite (Topa et al., 2021b) by both chemical composition (Table 5) and SXRD data (Table 3). Our finding of dewitite is also first in the Russian Federation.
Assemblage no. 3 hosts another phase chemically similar to dalnegroite. It forms short-prismatic crystals up to 60 x 5 ^m in size, as well as anhedral and euhedral grains up to 0.15 mm in size in calcite, orpiment, and realgar and often intergrowths with pyrite and routhierite. Macroscopically, this phase has
Cal
X
Ccp
Cpb
B 7 prp Cal puga
fH
Cal
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Fig. 17. Sulfosalts of the Vorontsovskoe deposit, part III:
a - short-prismatic dalnegroite crystal intergrown with routhierite in calcite; b - dewitite crystals and grains in quartz and calcite with realgar; c - clerite and parapierrotite grains in calcite; d - prismatic cupropolybasite crystal in chalcopyrite; e - polybasite grain between chalcopyrite and quartz; f - short-prismatic dufrenoysite crystal in calcite; g - «tennantite-(Mn)» and diopside rim around pyrite crystal; h - intergrowths of gillulyite with orpiment and gladkovskyite in calcite with a small routhierite grain; i - pseudomorphs of gladkovskyite after alabandite in calcite;j - gladkovskyite and lorandite aggregate in calcite; k - small guettardite and roshchinite inclusions in stibnite; 1 - dendritic hutchinsonite aggregates in calcite with dalnegroite and pyrite; m - acicular hutchinsonite crystal at the contact with wakabayshilite and realgar in calcite; n - imhofite and realgar grains in calcite; o - laffittite grain at the contact of stibnite with baryte in dolomite.
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4 6 3 10 12 14
As apfu
Fig. 18. As-Sb correlation in dalnegroite (1) and chabournéite (2) of the Vorontsovskoe deposit.
a black color and metallic luster; it is opaque, brittle, with an uneven fracture. Cleavage is absent. In reflected light, it is white with a faint pinkish tint, the reflectance values are lower than those of pyrite (R = 54 %), but higher than those of routhierite (R = 2830 %). Bireflectance is distinct. This phase is strongly anisotropic in bluish gray and brownish tones. Its chemical composition is characterized by widely variable Pb contents from Pb-free to Pb-rich varieties (Table 5 an. 38-39). The parameters of the triclinic unit cell of the Pb-free variety according to SXRD data (Table 3 No. 35) allow us to refer it to the chabournéite group (Miyawaki et al., 2021). A Sb branch of this group currently includes four mineral species: chabournéite (Johan et al., 1981; Biagioni et al., 2015; Makovicky et al., 2021; Miyawaki et al., 2021), protochabourné-ite (Orlandi et al., 2013; Miyawaki et al., 2021), dewi-tite (Topa et al., 2021b; Makovicky et al., 2021), and shimenite (Topa et al., 2021a), whereas an As branch contains only dalnegroite (Nestola et al., 2009; Bindi et al., 2010). The unit cell parameters with a volume four time smaller than that of dalnegroite and the chemical composition indicate that the phase from assemblage no. 3 could be the As analog of protochabournéite («protodalnegroite»).
Chalcostibite CuSbS2 was identified as 0.050.2 mm grains of stoichiometric composition overgrowing large (up to 5 mm) stibnite aggregates in limestone breccias (Sazonov et al., 1991a).
Christite TlHgAsS3 was found in assemblages nos. 1,3, and 4. It forms rounded grains up to 20 pm in size in gangue matrix of breccias (carbonates, ar-menite, baryte, clinochlore, muscovite, prehnite) (Fig. 1 lg). It is typically associated nearly with all abundant
ore minerals of above assemblages, as well as other Tl-and Hg-bearing sulfosalts. Christite is bright orange to dark orange, translucent, with an adamantine luster. Cleavage is perfect on {010}. The mineral is grayish white with a bluish tint and is distinctly anisotropic in brownish tones. The orange-red internal reflections are observed. The mineral is stoichiometric (Table 5). The identification is confirmed by SXRD data (Table 3). This is the first reliable finding of this mineral at the territory of the Russian Federation.
Clerite MnSb2S4 is the first new mineral described at the Vorontsovskoe deposit (Murzin et al., 1996). This Mn-analog of berthierite FeSb2S4 was found in silicified limestones from the core drilled in the central part of the deposit. Clerite occurs as isometric grains 0.01-0.2 mm in size, is mostly included in realgar or intergrown with aktashite and alabandite, and is associated with As-bearing pyrite, orpiment, stibnite, cinnabar, greigite, sphalerite, fahlores, zinkenite, chalcostibite, routhierite, and native gold. Murzin and Var-lamov (2010) noted the constant presence of As (up to 5 wt. %) in the composition of the mineral.
In our samples, clerite was found in assemblage no. 5 as anhedral grains up to 80 pm in size in Mn-bearing calcite and dolomite (Fig. 17c) and as tiny inclusions in baryte. Clerite is associated with luborzakite, aktashite, alabandite, boscardinite, chabourneite, native gold, orpiment, parapierrotite, pyrite, realgar, routhierite, Hg-Mn-bearing sphalerite, stibnite, and twinnite. In reflected light, clerite is white with a faint yellowish tint. Bireflectance is distinct in the air and strong in immersion. The effects of anisotropy are strong in yellow-brown tones. Clerite contains up to 4.6 wt. % As (Table 5). The parameters of the orthorhombic unit cell according to SXRD data (Table 3) are close to those calculated from PXRD by (Murzin et al., 1996).
Cupropolybasite [Cu6Sb2S7][Ag9CuS4] and poly-basite [Ag9CuS4][(Ag,Cu)6(Sb,As)2S7], two isostructural minerals of the polybasite series, were found in a sample consisting of calcite, quartz, chalcopyrite, pyrite, galena, and sphalerite, which was collected at the off-balance ore stockpile no. 2. Cupropolybasite forms long prismatic crystals up to 30 * 5 pm in size enclosed in chalcopyrite (Fig. 17d) and polybasite occurs as tabular crystals and grains up to 15 ><10 pm in size at the contact between chalcopyrite or pyrite and quartz (Fig. 17e). In addition to these minerals, this sample contained jalpaite and tetrahedrite-(Fe). Cupropolybasite and polybasite from the deposit are characterized by a wide isomorphism between Cu and Ag. Table 5 shows the chemical composition of the Cu-richest cupropoly-
basite and Ag-richestpolybasite. The optical properties of both minerals are almost identical. Their reflectance values are significantly lower than those of host chal-copyrite and pyrite, thus, at the contact with them, cu-propolybasite and polybasite look gray. Bireflectance and anisotropy effects in greenish and lilac tones are clearly visible in immersion. At high magnification, especially in immersion, cupropolybasite exhibits dark red internal reflections. The finding of cupropolybasite is probably the first in the Russian Federation.
Dufrenoysite Pb2As2S5 was tentatively identified in sample Vor-08/20-9 collected at off-balance ore stockpile no. 2 as rare inclusions up to 15 pm in size in calcite (Fig. 17f) in assemblage with native gold, pyrite, diopside, and fluorapatite. The mineral contains up to 6.9 wt. % Sb (Table 5). Its optical properties are consistent with dufrenoysite: white in reflected light and anisotropic in grayish violet tones.
Enargite Cu3AsS4 was mentioned in a gold-pyrite-realgar assemblage (Vikentyev et al., 2016), however, the chemical analyses most likely correspond to a mineral mixture.
Enneasartorite TlgPb32As70S140 and heptasar-torite Tl7Pb22As55S108 were determined in sample Vor-03/16-5-4 of assemblage no. 2 on the basis of chemical composition (Table 5). They compose rare prismatic crystals and grains up to 20 pm in size in a calcite-dolomite rock and are associated with minerals of the chabourneite-dalnegroite and vorontsovite-fer-rovorontsovite series, cinnabar, parapierrotite, pyrite, routhierite, and stibnite. The optical properties (white color and distinct anisotropy) correspond to minerals of the sartorite group. Both minerals were previously unknown at the territory of the Russian Federation.
Fahlores at the deposit form aggregates of rounded grains up to 0.1-0.3 mm in size in carbonates and are often intergrown with stibnite, pyrite, and zinke-nite (Sazonov et al., 1991a). The Ag-rich fahlores rim bournonite, boulangerite, chalcopyrite, and sphalerite. Small (up to 0.05 mm) fahlore crystals are locally enclosed in sphalerite. The chemical analyses provided by (Sazonov et al., 1991a) demonstrate a wide isomorphism between both the formally monovalent (Cu and Ag) and divalent (Fe and Zn) components. Their recalculation yields the compositions corresponding to seven members of the tetrahedrite group in accordance with a recently approved nomenclature (Biagioni et al., 2020): tennantite-(Fe), tennantite-(Zn), tetrahe-drite-(Fe), tetrahedrite-(Zn), argentotetrahedrite-(Fe), argentotetrahedrite-(Zn), and kenoargentotet-rahedrite-(Zn).
Murzin et al. (2011) reported on fahlores of variable composition as rounded or oval inclusions up to 5070 pm in size in native arsenic and arsenopyrite. Despite the presence of As-rich fahlores, both tennantite and tetrahedrite are recorded. The recalculated compositions correspond to tennantite-(Zn), tetrahedrite-(Zn), and a possibly new mineral «tetrahedrite-(Mn)» (Table 5). We also found the Fe-dominant members of the group in the same mineral assemblage: tennantite-(Fe) and tetrahedrite-(Fe). Tennantite-(Zn) was also identified as a rare accessory mineral in assemblages nos. 1, 4, 5, 7, and 9. In samples from assemblage no. 4, it composes anhedral grains and elongated inclusions up to 80 pm in stibnite with native arsenic (Fig. 8h), andor-ite, coloradoite, orpiment, realgar, and zinkenite. Assemblage no. 9 contains the largest (up to 2 * 2 cm) steel gray tennantite-(Zn) aggregates in quartz cavities with bayldonite, hemimorphite, malachite, and pyrite. This tennantite-(Zn) contains low amounts of Fe and Ag (Table 5) and the parameter of its cubic unit cell (Table 3) corresponds to the structural type of fahlores.
In assemblage no. 1, we found an elongated grain 40 x 15 pm in size at the margin of pyrite crystal overgrown by diopside, which corresponds to «tennantite-(Mn)», another possible new member of the tetrahedrite group (Fig. 17g; Table 5).
Geocronite Pb14(Sb,As)6S23 was first mentioned by Sazonov et al. (1991a). It forms aggregates <0.1 mm in size in gangue minerals of breccias or intergrowths with galena and arsenopyrite. The mineral was ascribed to geocronite on the basis of a ratio between main components and optical properties. Vikentyev et al. (2016) showed that the mineral contains a significant amount of As (up to 3.8 wt. % = 2.21 apfu). We found geocronite in samples with calcite-dolomite-quartz aggregates, galena, and sphalerite collected at off-balance ore stockpile no. 2. Geocronite forms anhedral grains up to 0.1 mm enclosed in galena or at the contact of the latter with quartz and is associated with benleonardite, hessite, and tsnigriite (Fig. lid). The As content in the mineral reaches 4.4 wt. % (Table 5).
Jordanite Pb14(As,Sb)6S23 was tentatively identified in assemblage no. 7 based on chemical data (Table 5). The mineral forms sporadic small (<7 pm in size) grains in dolomite and calcite and is associated with tsygankoite, alabandite, and tilasite. Although geocronite and jordanite often form continuous solid solution series (Moelo et al., 2008), they occur at the Vorontsovskoe deposit in different assemblages and show no intermediate compositions.
Gillulyite Tl2As75Sb03S13 is determined in assemblage no. 3, where it forms anhedral grains up to 80 pm and intergrowths up to 0.2 mm with gladkovskyite and orpiment in calcite (Fig. 17h). The mineral is dark red, translucent in thin sections, with adamantine luster. Perfect cleavage is observed along {001}. In reflected light, gillulyite is light gray; bireflectance is noticeable in air and strong in immersion in pale pink tones. The mineral looks dark red due to abundant bright red internal reflections and is distinctly anisotropic in gray and brownish tones. The chemical composition and parameters of the monoclinic unit cell of gillulyite are given in Tables 5 and 3, respectively. In the Raman spectrum (Fig. 13b), a range of 240400 cm1 corresponds to the stretching vibrations of As-S bonds. The lower-frequency bands are assigned to the mixed lattice modes involving bending vibrations of the As,Sb,S-bond system and stretching vibrations of Tl-As and Tl-S bonds. Unlike auerbakhite and gladkovskyite, in spectra of which the strongest peaks are observed at 384-387 cm1 due to the contribution of vibrations of Mn-S bond, the strongest peaks in gil-lulyite (as in hutchinsonite) are observed in the lower frequency region. Our finding of gillulyite is the first in the Russian Federation and second in the world after its type locality, South Mercur Pit in Utah, USA (Wilson et al., 1991). In addition to a chemically «normal» gillulyite, which contains only 0.2-0.3 apfu Sb similarly to the Utah holotype, we detected few rare small (up to 20 x 20 pm) grains of a Sb-rich gillulyite (up to 3.43 apfu Sb; Table 5, an. 53).
Gladkovskyite MnTlAs3S6 is a new sulfosalt described at the Vorontsovskoe deposit (Kasatkin et al., 2019). It honors the discoverer of the deposit Boris Aleksandrovich Gladkovsky (1937-1990). The mineral occurs in limestone breccias enclosed in abundant realgar, orpiment, baryte, and pyrite, as well as minor clinochlore, fluorapatite, quartz, and talc. Glad-kovskyite occurs as long-prismatic crystals and grains up to 0.2 mm in realgar and orpiment (Fig. 16b) and, locally, forms partial pseudomorphs after alabandite (Fig. 17i) and intergrowths with gillulyite and loran-dite (Figs. 17h, 17j). In one sample, we found a gladkovskyite veinlet 2 mm long and up to 0.3 mm thick in calcite.
The mineral is transparent and has a dark cherry red color, a red streak and an adamantine luster. It is brittle, with uneven fracture and neither cleavage nor parting. The Vickers microhardness is 94 kg/mm2 corresponding to a Mohs hardness of 2-2'A The calculated density is 4.356 g/cm3. In reflected light, the mineral looks
Fig. 19. Crystal structure of gladkovskyite.
Purple - T1S9 polyhedra, turquoise - Mn-centered octahedra, ball-and-stick model representation (green As and yellow S atoms) - AsS3 pyramids. All S atoms are shown as thermal ellipsoids.
light gray; bireflectance is barely noticeable. The mineral is strongly anisotropic with clear effects in dark gray, light gray and brownish tones. Some grains look dark red due to abundant bright red internal reflections, especially intense in immersion. In transmitted light, gladkovskyite is strongly pleochroic from orange-red to dark red. The reflectance spectra are shown in Fig. 12. The reflectance values for wavelengths recommended by the Commission on Ore Mineralogy of the IMA are as follows (R IR ,%): 23.6/25.5 (470 nm),
v min max' ' v
23.3/23.5 (546 nm), 22.3/22.4 (589 nm), 21.1/21.7 (650 nm). The chemical composition of the holotype sample is given in Table 5. Its empirical formula based on the sum of all atoms of 11 is Mn101(Tl099Pb001)100 (As286Sb013)299S600. Gladkovskyite is trigonal, R31c, Z = 2. The unit cell parameters are given in Table 3. The strongest reflections of the PXRD pattern are as follows [d, A (I, %) (hkl)\. 5.11(80)(101), 4.83(70) (110), 3.49(50)(201), 3.23(30)(002), 2.86(100)(-2-ll, 211), 2.68(30)(112), 2.55(60) (301, 202).
The Raman spectrum of gladkovskyite is similar to that of auerbakhite (Fig. 13c). The bands of Mn-S stretching vibrations are observed in a range 350400 cm-1. The bands at 289 and 305 cm-1 are assigned to As-S stretching vibrations. The Raman bands with wavenumbers below 250 cm-1 are possibly related to mixed soft modes involving bending vibrations and Tl-As and Tl-S stretching vibrations and phonons. The crystal structure of gladkovskyite belongs to rare
cyclic sulfosalts and contains infinite chains of face-sharing MnS6 octahedra, TlS9 polyhedra and pyramidal AsS3 groups (Fig. 19).
Guettardite PbAsSbS4 was identified in five mineral assemblages. It forms rare small (typically <10 pm in size) inclusions in orpiment, stibnite, and gangue minerals of breccias (calcite, dolomite, baryte, quartz, clinochlore, fluorapatite). It is also associated with aktashite, cinnabar, coloradoite, native gold, laffittite, metacinnabar, pyrite, realgar, routhier-ite, sphalerite, and other minerals. In assemblage no. 1, the guettardite inclusions up to 30 pm were found in chabournéite and écrinsite (Fig. llh) and, in assemblage no. 4, guettardite is intergrown with roshchinite (Fig. 17k). In reflected light, guettardite is white with a bluish tint; bireflectance is distinct. It is strongly anisotropic in brownish tones. Several larger grains exhibit weak reddish internal reflections. The chemical composition ofthe mineral is close to stoichiometric PbAsSbS4 (Table 5). This is the first finding of the minerals at the Russian Federation.
Gungerite TlAs5Sb4S13 is a new mineral found at the Vorontsovskoe deposit (Kasatkin et al., 2020c, 2022a). The mineral was named after Yuri Vladimi-rovich Gunger (born in 1961), a mining engineer and surveyor, a famous historian and expert of Northern Urals, a former director of the Fedorov Geological Museum in Krasnoturyinsk. Gungerite was found in limestone breccias mainly composed of calcite and dolomite and enclosed in orpiment, pyrite, realgar, and stibnite and minor baryte and quartz. Gungerite is associated with bernardite, minerals of the chabournéite-dalnegroite and vorontsovite-ferrovorontsovite series, cinnabar, coloradoite, native gold, greigite, hutchin-sonite, parapierrotite, and routhierite. Amid all new minerals found at the deposit, only gungerite forms macroscopic fine-grained bright orange aggregates up to 0.5 x 0.2 cm size on the breccia surface (Figs. 16c, 16d). The mineral has an orange streak, a greasy luster and a perfect cleavage on {010}; it is translucent in thin fragments. Gungerite is brittle, with an uneven fracture. The Vickers microhardness is 84 kg/mm2 corresponding to a Mohs hardness of 2-2^. The calculated density is 4.173 g/cm3. In reflected light, gungerite is yellowish white, but looks light gray with a weak bluish tint at the contact with stibnite. Bireflectance is very weak. The mineral is distinctly anisotropic, but anisotropy effects are masked by bright orange internal reflections. The internal reflections are visible even in plane-polarized light and are extremely abundant and strong in cross-polarized light in air and, especially,
Fig. 20. Crystal structure of gungerite projected along [010].
Axes a and c are horizontal and vertical, respectively. The space between the rods is filled with lone-electron Sb and As pairs . Yellow, blue, red, and brown - S, Tl, Sb and As, respectively; lilac - covalent As-As bonds.
in immersion. The reflectance spectra are shown in Fig. 12. The reflectance values for the wavelengths recommended by the Commission on Ore Mineralogy of the IMA are as follows (R . IR , %): 27.0/29.8
i=>J v min max' '
(470 nm), 26.1/27.4 (546 nm), 24.5/25.9 (589 nm), 22.4/23.9 (650 nm).
The chemical composition of the holotype sample is given in Table 5. Its empirical formula based on the sum of all atoms of 23 is Tl099As529Sb3 77S12 95. Gungerite is orthorhombic, space group Pbcn, Z = 8. The unit cell parameters are given in Table 3. The strongest reflections of its PXRD pattern are as follows [d, A (I, %) (hkl)]: 5.755(100)(020), 3.030(10)(424), 2.901(10)(620), 2.878(14)(040), 2.821(10)(141).
According to the current nomenclature of sulfo-salts (Moelo et al., 2008), gungerite belongs to a rare class of subchalcogenides, which are characterized by a S deficiency relative to those with «normal» valences and relative excess of positive charges with respect to the charge balance (+2 for the ideal formula of gunge-rite, when the charge loss due to the covalent As-As bonding is ignored). The crystal structure of gungerite (Fig. 20) is the most complex among all new sulfosalts of the deposit. It contains 23 atomic sites, in which one site is occupied by Tl, one site is occupied by Sb, three
sites are occupied by As, three Sb and two As sites are mixed-occupied and remaining 13 sites are occupied
by S atoms.
The crystal structure consists of (As,Sb)-S clusters, which have van der Waals contacts to most surroundings, and are connected to them only by sparse metal cation-sulfur bonds (Kasatkin et al., 2022a). These clusters have a peculiar arrangement, being «stacked» on, around, and along the Tl-S rods parallel to [010]. An individual cluster, always doughnut-shaped (or toroid-shaped), has a central Tl polyhedron half-inserted into it. The cluster is formed by a chelating mirror-symmetrical group that has Sb-As «defect coordination cubes» as forceps (with some atoms missing from a perfect cube-model). Its two mirror-related arms are connected by the coordination pyramid of As3. One arm of the chelating group has an eyelet of doubly interconnected Sb1 and Sb3 as its terminal portion. Through the coordination pyramid of Asl, the eyelet is connected to the centrally positioned pyramid of As3, from which starts the other arm of the chelating group. In the order of appearance, this arm consists of the coordination pyramid of As2, a terminal eyelet of Sb2 and Sb4. These two Sb atoms are doubly interconnected via two sulfurs. A radially oriented «tail group» points out of the cluster and is formed by a covalent As-As bond, which connects As3 with As4. After the As4 polyhedron (which still is in a mirror-symmetric position with the rest of the «molecule») As5 follows, which points sideways, counter to the m symmetry of the group. An As5 polyhedron from an adjacent «molecule», however, is a mirror-symmetrical «plug» that closes the doughnut body from the side, which was left open by the original group.
In the Raman spectrum of gungerite (Fig. 13d), the wavenumbers in a range of 280-370 cm-1 refer to as As-S stretching vibrations. A strong band at 294 cm-1 with a shoulder at 240 cm-1 can be assigned to the bending mode of SbS3 units (Frost et al., 2010). The bands in the ranges of 302-310, 334, 282, and 270 cm-1 are assigned to antisymmetric, symmetric, symmetric, and antisymmetric bending modes of SbS3, respectively (Kharbish et al., 2009). It is noteworthy that no strong Raman bands of Tl sulfosalts, except for gungerite, are observed in a range of 250-265 cm-1 in the literature (Kharbish, 2011; Makreski et al., 2014) and our Raman spectra. Unlike other Sb-bearing Tl sulfosalts with pyramidal (As,Sb)S3 units, gungerite is characterized by the presence of a As-As bond in the crystal structure and the presence of a strong band at 263 cm-1 in the Raman spectrum. Thus, the band at 263 cm-1 was as-
signed to As-As stretching vibrations that is in good agreement with the Raman spectrum of arsenolamprite with the strongest Raman band observed at 253 cm-1 (Thomas, Davidson, 2010). The assignment of the Raman bands with wavenumbers below 250 cm-1 is ambiguous and, probably, they correspond to soft mixed lattice modes involving As-S-As bending and Tl-S stretching vibrations.
Heteromorphite Pb7SbgS19was found in a complex aggregate of sulfantimonites and galena in a sample collected at off-balance ore stockpile no. 2. The mineral forms grains up to 0.12 mm in sphalerite, which are intergrown with galena and boulangerite (Fig. 1 li), and is associated with plagionite, semseyite, and pyrite. It contains low As and Se amounts (Table 5) and the atomic Pb/(Sb+As) ratio ranges from 0.910 to 0.935, which is within a Pb/Sb range (0.86-0.96) for heteromorphite from various deposits (Mozgova et al., 1971). In reflected light, heteromorphite is white, almost identical in brightness to galena and boulange-rite, slightly darker than pyrite, but much brighter than sphalerite. Its bireflectance is strong. Heteromorphite differs from all neighboring minerals by strong anisot-ropy effects in brownish-yellowish and greenish tones. Several references to heteromorphite findings in Russia (Ivashchenko et al., 2004; Bryzgalov et al., 2011; Kemkina et al., 2018; Gvozdev et al., 2020) provide no sufficient information for its precise identification. Thus, we consider our finding at the Vorontsovskoe deposit the first reliable in Russia.
Hutchinsonite TlPbAs5S9 is a rare mineral identified in assemblages nos. 1, 2, and 3. In each assemblage, it is characterized by specific morphology. In assemblage no. 1, the mineral composes dendritic aggregates up to 0.2 x 0.1 mm in size in a calcite-prehnite rock and is associated with pyrite, realgar, dalnegroite, native gold, routhierite, sphalerite, baryte, and fluorapatite (Fig. 171). In assemblage no. 2, hutchinsonite forms long-prismatic to acicular crystals up to 50 * 5 pm in size in calcite and, locally, is intergrown with realgar and wakabayashilite (Fig. 17m). In assemblage no. 3, hutchinsonite occurs as dissemination of tiny grains (<15 pmin size) in calcite.
The mineral has a cherry red color and an adamantine luster and it is translucent in thin sections. A good cleavage on {010} is observed. In reflected light, hutchinsonite is bluish gray; its bireflectance is distinct. It is strongly anisotropic in bluish and brownish tones. The internal reflections are carmine red, especially strong in immersion. Hutchinsonite from all assemblages contains a low Sb amount (Table 5). The
parameters of its orthorhombic unit cell are given in Table 3. In the Raman spectrum (Fig. 13g), a range of 280-400 cm-1 corresponds to the stretching vibrations of As-S bonds. The bands with lower wavenumbers cannot unambiguously be assigned and are probably related to mixed lattice modes involving bending vibrations of As-S bonds, as well as the stretching vibrations of the T1 and Pb coordination polyhedra (these vibrations can resonate with each other and cover large regions in the crystal). Our finding of hutchinsonite is the first in Russia.
Imhofite Tl5gAs154S26 was determined in assemblages nos. 1 and 3, where it composes rare anhedral grains up to 30 pm in size in calcite with realgar (Fig. 17n). The mineral is bright red; it is translucent in thin fragments. In reflected light, imhofite is light gray; bi-reflectance is weak in the air and distinct in immersion. Strong anisotropy in grayish-brownish tones and red internal reflections are observed. The chemical composition of the mineral and its monoclinic unit-cell parameters are given in Tables 5 and 3, respectively. Imhofite was discovered in the Lengenbach quarry (Burri et al., 1965) and was later described in the Shi-men deposit, China (Roth et al., 2017). Our finding is, thus, the first in the Russian Federation and, most likely, third in the world.
Laffittite AgHgAsS3 was found in assemblage no. 4 as individual grains up to 30 pm in size in dolomite and baryte or in aggregates with stibnite (Fig. 17o). It is associated with coloradoite, guettardite, orpiment, parapierrotite, and roshchinite. Laffitite is transparent and has a dark red color and an adamantine luster. In reflected light, the mineral is bluish white. It is moderately anisotropic from bluish gray to dark gray; the effects of anisotropy are strongly enhanced in immersion. The red internal reflections are distinct. The chemical composition of the mineral is close to theoretical (Table 5). This is the first finding of laffittite in the Russian Federation.
Lillianite Pb3Bi2S6 forms rare inclusions up to 20 pm in size in magnetite and intergrowths of the same size with Te-bearing ikunolite from assemblage no. 8. In reflected light, the mineral is creamy white. It is distinctly anisotropic with more intense effects than of the neighboring ikunolite. Lillianite also demonstrates a typical so-called «gustavite» isomorphic substitution according to 2Pb2+ ^ Ag++Bi3+ scheme (Makovicky, 2019) (Table 5); the substitution percentage Z%is 72.3.
Lorandite TlAsS2 was identified in assemblage no. 3 as individual grains up to 20 pm in size included in calcite, as well as the intergrowths with gladkovskyite
up to 50 pm in size (Fig. 17j) and with philrothite and orpiment up to 0.1 mm in size. The mineral is bright red, transparent, with an adamantine luster, very brittie. Cleavage is perfect on {100} and good on {001} and {201}. In reflected light, lorandite is grayish white, slightly lighter than gladkovskyite and philrothite. No bireflectance is observed in the air in contrast to immersion. Lorandite exhibits strong anisotropy in yellowish-brownish tones, but anisotropy in some grains is masked by abundant red internal reflections. The chemical composition of the mineral is stoichiometric (Table 5).
The strong reflections of the PXRD pattern are as follows [d, A (I)]: 5.25(20), 3.80(20), 3.57(100), 2.99(20), 2.88(90), 2.63(30), 2.37(10), 1.85(10). The parameters of the monoclinic unit cell (Table 3) are almost identical to those oflorandite from the type locality Allchar deposit in North Macedonia (Fleet, 1973). The Raman spectrum (Fig. 13e) corresponds to that of lorandite (Kharbish, 2011; Makreski et al., 2014). All bands in a range of 250-400 cm-1 are due to vibrations of As-S bonds: a strong band at 397 cm-1 and a most intense band at 379 cm-1 (as well as a weak band at 353 cm-1) are assigned to v1 (symmetric stretching vibrations) and v3 (antisymmetric stretching vibrations), respectively. A strong band at 324 cm-1 with a shoulder at 310 cm-1 and a strong band at 275 cm-1 are assigned to v2 (symmetric bending vibrations) and v4 (antisymmetric bending vibrations), respectively. The wave-numbers below 210 cm-1 correspond to mixed lattice modes. In Russia, lorandite was mentioned in assemblage with lermontovite without optical or analytical data at the Beshtau U deposit in Northern Caucasus (Melkov et al., 1983). Thus, we consider our data the first reliable for lorandite in the Russian Federation.
Luborzakite Mn2AsSbS5 is a second new mineral without species-defining T1 discovered at the deposit (Kasatkin et al., 2020a) after clerite. It honors Lubor Zak (1925-2008), a prominent Czech crystallographer and mineralogist, an expert in sulfosalts, and Professor at the Faculty of Science of the Charles University in Prague. Luborzakite forms long-prismatic crystals up to 70 x 20 pm in size and similar-sized anhedral grains in Mn-bearing dolomite and calcite (Fig. 21a). Luborzakite is associated with pyrite, orpiment, realgar, stibnite, aktashite, alabandite, boscardinite, chabourne-ite, coloradoite, clerite, ecrinsite, native gold, routhie-rite, sphalerite, twinnite, baryte, chernovite-(Y), diop-side, fluorapatite, hyalophane, muscovite, and prehnite.
Luborzakite is black, opaque with a metallic luster and a black streak. It is brittle and has an uneven frac-
a Cal f * ' B
u 1 « Mgt \ tk t Pav f
a
t
> : a
Fig. 27. Sulfosalts of the Vorontsovskoe deposit, part IV:
a - long-prismatic luborzakite crystal in carbonate aggregate; b -intergrowth of luborzakite, its Pb-rich variety (Lbr?), ecrinsite, and realgar in Mn-bearing calcite and dolomite; c - oyonite grain in calcite with realgar; d - parapierrotite crystals in calcite; e - aggregate of parapierrotite, stibnite, realgar and cinnabar in dolomite; f- aggregate of pavonite andjoseite-A in magnetite; g- prismatic philrothite crystals in calcite; h-pokhodyashinite (1) with parapierrotite (2), pyrite (3), sphalerite (4), dalnegroite (5), routhierite (6), realgar (7), weissbergite (8) in calcite (9) with clinochlore (10).
BSE images.
ture. No cleavage and parting were observed. The Vick-ers microhardness (VHN, 30 g load) is 242 kg/mm2 corresponding to a Mohs hardness of 4-4'A The calculated density is 4.181 g/cm-3. In reflected light, luborzakite is tin white; bireflectance is moderate. It is distinctly anisotropic with rotation tints varying from light gray to brownish. Kasatkin et al. (2020a) described no internal reflections, however, red internal reflections, especially noticeable in immersion, were observed in recently found larger grains (up to 80 * 50 pm in size). The reflectance spectra are shown in Fig. 12. The reflectance values for the wavelengths recommended by the Commission on Ore Mineralogy of the IMA are as follows (RmJRmx, %): 23.6/25.3 (470 nm), 22.4/24.7 (546 nm), 22T/24.3 (589 nm), 21.8/23.8 (650 nm).
The chemical composition of the holotype sam-pie is shown in Table 5. Its empirical formula based on the sum of all atoms of 9 is Mn186Pb0 04Ag003Cu002 As098Sb107S500. Luborzakite is monoclinic, space group C2/m, Z=4. The unit cell parameters are given in Table 3. The crystal structure of luborzakite (Fig. 22) contains ten atomic sites with one Sb site, one Mn site, five S sites and three mixed-occupied sites (two As/Mn and one Mn/Sb sites). The structural formula of the mineral is [Mn05SbS2]thin-layer • [(Mn,Sb)05(AsMn)S2S3]thick-layer individualizes two layers in its structure.
Luborzakite is a new member of the pavonite homologue series with N= 5. These structures resemble the unit-cell-twinned lillianite, in which slabs of PbS-like arrangement are cut along (311)pbs and twinned using
Fig. 22. Projection of the crystal structure of luborzakite downb.
Only strong short bonds are indicated.
these planes via bi-capped trigonal coordination prisms (mostly, of Pb). In the pavonite series, one orientation of these slabs is always only one octahedron-wide, whereas the other intervening slab orientation can be several cation-coordination octahedra wide (up to eight octahedra). The bi-capped trigonal coordination prisms on twin planes become distorted and are usually occupied by the lone electron pair of Bi (or Sb) situated in one of the prism's caps. In luborzakite, the thinner layer's octahedron is occupied by Mn3, whereas the caps of 'empty' only moderately distorted trigonal coordination prisms have the cap oriented into this layer filled by a coordination prism ofSbl.
In one aggregate about 0.2 mm long consisting of luborzakite, ecrinsite, and realgar, we identified a phase optically similar to luborzakite differing in a significant Pb content, a deficiency of Mn and a distinct Sb/As ratio (Table 5, an. 73). An intimate intergrowth of this phase with other minerals (Fig. 21b) prevent from its XRD studies. Another clerite-like phase with formula Mn(Sb,As)S4 was previously noted in assemblage with clerite (Murzin, Varlamov, 2010). In comparison with luborzakite, it has lower Mn and higher Sb contents.
Manganoquadratite AgMnAsS3 was identified by chemical composition (Table 5) as rare inclusions about 10 pm in size in sphalerite in assemblage no. 1. In reflected light, the mineral looks light gray, noticeably lighter than the host sphalerite. No additional optical characteristics are determined due to a small grain size of manganoquadratite. Our finding of this mineral is the first in Russia and third in the world after its type locality Uchucchacua Mine in Peru (Bonazzi et al., 2012) and Sacaramb deposit in Romania (Dinca, Popescu, 2019).
Meneghinite Pb13CuSb7S24 was found in samples from the dumps of the southern open pit. It forms lead gray pockets up to 1 x 0.5 cm in calcite in assemblage with cubic pyrite crystals and white talc coatings (Fig. 16e). In reflected light, meneghinite is white. It is strongly anisotropic in greenish tones. The chemical composition of the mineral is stoichiometric (Table 5). The strong reflections of the PXRD pattern are as follows [d, A (I)]: 5.81(30), 3.87(40), 3.70(50), 3.48(70), 3.27(90), 2.93(100), 2.73(70), 2.54(10), 2.08(60). The parameters of the orthorhombic unit cell correspond to meneghinite (Table 3).
Oyonite Ag3Mn2Pb4Sb7As4S24 was identified by chemical composition in assemblage no. 1 (Table 5). It occurs as a single grain 30 * 15 pm in size, which is enclosed in calcite with realgar, boscardinite, colo-radoite, pyrite, sphalerite, stibnite, and twinnite (Fig. 21c). In reflected light, oyonite is grayish white, significantly brighter than the hosting realgar. It exhibits a distinct anisotropy in grayish and brownish tones. This is the first finding of the mineral in Russia and second in the world after its type locality the Uchucchacua Ag mine in Peru (Bindi et al., 2018).
Parapierrotite TlSb5S8 is one of the five most abundant Tl minerals at the deposit along with cha-bourneite, dalnegroite, routhierite, and vorontsovite. Murzin and Varlamov (2010) first reported on the chemical composition of a Tl sulfosalt that was conditionally ascribed to pierrotite or parapierrotite. We found parapierrotite in five assemblages. In assemblages nos. 2 and 4, abundant parapierrotite forms short-prismatic black crystals with a metallic luster and anhedral grains in gangue minerals of breccias (calcite, dolomite, baryte, quartz, clinochlore, prehnite, diopside, etc.) and is associated with cinnabar, orpiment, pyrite, realgar, routhierite, cinnabar, minerals of the vorontsovite-ferrovorontsovite and chabourne-ite-dalnegroite series, etc. The largest individuals of parapierrotite reaching 1 mm in size were found in assemblage no. 4 (Fig. 21d). The mineral structure
Fig. 23. Sb-Ascorrelationinparapierrotite.
Fig. 24. Crystal structure of parapierrotite along [-101]. Black - Tl atoms, light gray - Sb and As sites, yellow -S atoms. Black lines - unit-cell edges.
was solved using one of these large crystals (Plasil et al., 2018). Smaller parapierrotite grains often occur as inclusions in pyrite and intergrowths with realgar, stibnite, and cinnabar (Fig. 21e). In reflected light, the mineral is white with a weak grayish tint; bireflectance is moderate. It is distinctly anisotropic in gray brownish and gray bluish tones. Red internal reflections are rare. The As content of the mineral widely varies from 2.0 (0.28 apfu) to 17.6 (2.23 apfu) wt. % (Table 5). The Sb-As isomorphic substitution extends from Sb94As6
to Sb53As47 with an obvious miscibility gap between Sb88As12 and Sb77As23 (Fig. 23).
The crystal structure of the natural parapierrotite (Fig. 24) is identical to a structure of a synthetic phase TlSb5S8 (Engel, 1980), in which Tl occupies two sites, whereas 10 and 16 sites are occupied by Sb and S, respectively. The refinement of the structure of parapierrotite from the Vorontsovskoe deposit shows that As isomorphically substitutes for Sb only in half of ten sites (Plasil et al., 2018). The reasons of partial ordering of As and Sb atoms are related to a stereochemical behavior of Sb3+ and the formation of more clear-cut AsS3 pyramids in comparison with Sb3+. Substitution of some Sb3+ atoms by smaller As3+ ones obviously leads to a decrease in the volume of the unit cell of the mineral. The more significant the decrease, the higher the As3+ content in the composition of the mineral (Table 3). In addition, our SXRD experiments with parapierrotite grains of various chemical compositions show that the XRD quality also directly depends on the Sb/As ratio of the mineral: the larger the As content, the worse the X-ray pattern. As a result, a crystal with a minimum As content (2.0 wt. %) yielded the best structural data.
Parapierrotite is rare in assemblage no. 5. It composes prismatic crystals up to 50 pm in size in aggregates of Mn-bearing carbonates and is associated with clerite (Fig. 17c), luborzakite, alabandite, pyrite, and realgar. An interesting feature of parapierrotite is the presence of Mn up to 1.6 wt. % (0.28 apfu) and a deficiency in Sb and As sites: 4.71-4.74 apfu Sb + As (Table 5, an. 88-89). By analogy with luborzakite, it is suggested that the deficiency is compensated by isomorphic entry of Mn in some of the Sb/As sites. The finding of parapierrotite at the Vorontsovskoe deposit is the first in the Russian Federation.
Pavonite AgBi3S5 forms anhedral grains up to 30 pm in size and intergrowths with joseite-A up to 50 pm in size in magnetite from assemblage no. 8 (Fig. 21f). In reflected light, pavonite is white at the contact with magnetite and has a faint pinkish cream tint at the contact withjoseite-A. The effects of anisot-ropy in pavonite are more intense than in joseite-A, in bluish gray tones. Bireflectance is weak in the air and significant in immersion. The mineral contains a low Pb contents (Table 5).
Philrothite TlAs3S5 was identified in assemblages nos. 1 and 3 of carbonate breccias, where it forms scarce short-prismatic crystals up to 70 * 15 pm in size in calcite and dolomite (Fig. 21g). In rare cases, philrothite is intergrown with lorandite, realgar and
rounded grains of native gold. The mineral is black and opaque. In reflected light, it looks light gray, slightly darker than neighboring lorandite but brighter than realgar. Bireflectance in the air is noticeable. The mineral is strongly anisotropic in light gray and brown tones. The chemical composition and parameters of the mon-oclinic unit cell of philrothite are given in Tables 5 and 3, respectively. This is the first finding of this mineral in the Russian Federation and second world finding after its type locality at the Lengenbach quarry (Bindi et al., 2014).
Pierrotite Tl2(Sb,As)10S16was described as rounded or anhedral inclusions up to 60 * 30 pm in size in large (up to 3 mm) realgar aggregates (Sazonov et al., 1991a). In reflected light, it is white with a greenish or bluish tint. The anisotropy is distinct. The internal reflections are dark red. The chemical formula provided by these authors (Tl186 Ag
0.01 Cu0.11 Fe0.02)2.00(As7.20
Sb3 72)10 92S16 08, however, does not correspond to pierrotite, because the latter is a Sb-dominant mineral. We believe that the indicated optical and chemical data better match bernardite, although this suggestion requires the XRD study. Murzin and Varlamov (2010) reported on the chemical composition of a Tl sulfosalt, which is consistent with both pierrotite and parapierro-tite. We cannot exclude the presence of pierrotite in ores of the Vorontsovskoe deposit due to its chemical composition and optical data similar to parapierrotite, however, all 15 grains of the mineral studied by XRD were parapierrotite.
Plagionite Pb5SbgS17 forms prismatic crystals or anhedral grains less than 0.1 mm in size in quartz or carbonates of breccias (Sazonov et al., 1991a). It is occasionally recorded from the central parts of zonal intergrowths with other sulfides. Plagionite was determined by its chemical composition and optical properties. It was identified in an aggregate of sulfantimo-nites and galena in a sample collected at off-balance ore stockpile no. 2. Plagionite occurs as grains up to 50 pm in sphalerite or at the contact with galena and pyrite (Fig. lli) and is associated with boulangerite, heteromorphite, and semseyite. The mineral contains minor Bi and Se amounts (Table 5). Plagionite is creamy white in reflected light, slightly darker than galena in the air and much darker in immersion. Bireflectance is distinct. The effects of anisotropy are strong (especially, in immersion) in gray, pinkish and brownish tones.The red-brown internal reflections are also observed in immersion.
Pokhodyashinite CuTlSb2(Sb1-xTlx)AsS7-x is the rarest new mineral of the Vorontsovskoe deposit (Ka-
satkin et al., 2022b). It was found in two polished sections of carbonate breccia collected at the main ore stockpile. The new mineral is named in honor ofMak-sim Mikhailovich Pokhodyashin (1708-1780), a Russian merchant, manufacturer, and owner of mines and smelter plants in Northern Urals. He was a pioneer of mining engineering and smelting works in the region, who founded the Bogoslovskiy mining district, opened and operated famous Turyinsk copper mines, established three copper smelters, and built important roads connecting the mines and the smelters. Pokhodyashinite forms anhedral grains up to 0.1 x 0.05 mm in size in calcite and is associated with major orpiment, pyrite and, realgar and minor baryte, clinochlore, As-bearing fluorapatite, harmotome, prehnite, arsiccioite, boscar-dinite, chabourneite, coloradoite, dalnegroite, ecrinsite, native gold, parapierrotite, routhierite, sicherite, sphalerite, stalderite, tennantite-(Zn), and weissbergite in assemblage no. 1 (Fig. 21h).
Pokhodyashinite is black, opaque, with a metallic luster and a black streak. It is brittle, with an uneven fracture and a poor cleavage on {010}. The Vickers hardness (VHN, 20 g load) is 55 kg/mm2 corresponding to a Mohs hardness of 2. The calculated density is 5.169 g/cm3. In reflected light, pokhodyashinite is grayish white, bireflectance is distinct. It is strongly anisotropic; rotation tints vary from dark brownish gray to light bluish gray. No internal reflections are observed. The reflectance spectra are shown in Fig. 12. The reflectance values for the wavelengths recommended by the Commission on Ore Mineralogy of the IMA are as follows (R JR , %): 28.9/34.6 (470 nm), 27.6/33.4
min max
(546 nm), 26.7/32.4 (589 nm), 26.1/31.1 (650 nm).
The chemical composition of the holotype sample is shown in Table 5. Its empirical formula based on the sum of all cations of 6 is Cun7nAgn,,Tl, „PbnnoSb,,„
0.70 C30.34 1.32 0.02 2.63
As099S6 625. Pokhodyashinite is monoclinic, space group C2/m, Z = 4. The unit cell parameters are given in Table 3. The structure of pokhodyashinite contains 13 atomic sites: one Tl, two Sb, one As, seven S, and two mixed-(one Sb/Tl and one Cu/Ag) sites (Fig. 25). Its structure can be described as wavy slabs of a complex structure based on double-rods of (primarily) Sb-coordination pyramids and lone-electron-pair interspaces/micelles, separated by wavy interlayers consisting of paired columns of Tl and rods of paired Cu-coordination polyhedra.
Ramdohrite (Cd,Mn,Fe)Ag55Pb12Sb215S48 was probably found in assemblage no. 6 as tiny inclusions up to 8 pm in size in an arsenopyrite grain, which is enclosed in vesuvianite (Fig. 26a). The mineral con-
Fig. 25. Projection of the crystal structure of pokhodyashinite along [010] (slightly inclined).
Blue, azure, orange, red, and yellow - Tl, Cu/Ag, Sb, As, and S atoms, respectively. The unit-cell edges are indicated.
tains Mn, Cu, Fe, and Zn, which possibly substitute to Ag (Table 5).
Rebulite Tl5Sb5As8S22 was determined in assemblages nos. 1 and 3. The mineral occurs as rare prismatic individuals up to 20 pm long and angular grains up to 40 x 30 pm in size in calcite-quartz aggregates. It is observed together with boscardinite, chabourne-ite, orpiment, parapierrotite, pyrite, realgar, routhierite, Mn-Hg-bearing sphalerite, baryte, diopside, prehnite, and fluorapatite (Fig. 26b). Sample Vor-SS-10 from assemblage no. 1 contained one large rebulite grain (0.2 x 0.1 mm in size) with a small inclusion of vrbaite (Fig. 26c). Rebulite has a dark red color and a luster varying from metallic to adamantine. In reflected light, it is grayish white. It is distinctly anisotropic in grayish and brownish tones with red internal reflections.
The chemical composition of the mineral and the parameters of its monoclinic unit cell are given in Tables 5 and 3, respectively. Its Raman spectrum (Fig. 13f) is identical to that of rebulite described by (Makreski et al., 2014). The bands with maxima in a range of 330-400 cm1 are assigned to As-S and Sb-S stretching (Vj + v3) vibrations and the bands with maxima at 322 and 250 cm-1 are due to bending (v2 + v4)
vibrations of short (2.2-2.6 A) and long (2.9-3.9 A) Sb-S bonds, respectively. The bands below 205 cm-1 belong to the mixed lattice modes. Rebulite was first described at the Allchar deposit (Balic-Zunic et al., 1982) and remained its endemic for a long time. In the late 2010s, it was also discovered at the Shimen As deposit in the Hunan province, China (Roth et al., 2017). Our finding is the first in Russia and third in the world.
Roshchinite Ag19Pb10Sb51S96 was probably found in one sample from assemblage no. 4, which was composed of dolomite, baryte, and large (up to 3 mm) stib-nite aggregates. Roshchinite is included in stibnite and is intergrown with guettardite (Fig. 17k). The sizes of the individual inclusions and intergrowths do not exceed 20 and 15 pm, respectively. It is also associated with coloradoite, laffittite, orpiment, and parapierrotite. Roschinite contains Mn (up to 0.2 wt. %), Hg (up to 3.0 wt. %), and As (up tol 1.4 wt. %) (Table 5). The lower contents of the same trace elements (up to 0.04, 0.9, and 5.6 wt. %, respectively) were also determined in roshchinite from its type locality at the Kvartsitovye Gorki Au deposit in Northern Kazakhstan (Spiridonov et al., 1990).
The optical properties of the studied mineral are consistent with those of roshchinite: it is grayish white with a slightly bluish tint in reflected light and is moderately anisotropic without color effects. In terms of the reflectance values, roshchinite is close to guettardite and host stibnite but is characterized by weaker (almost invisible) bireflectance and weaker anisotropy. Small grain size of roshchinite prevented from XRD studies. Our finding of this sulfosalt is probably the first in the Russian Federation.
Routhierite Tl(Cu,Ag)(Hg,Zn)2(As,Sb)2S6 together with chabourneite, dalnegroite, parapierrotite, and vorontsovite is one of the most abundant Tl sulfo-salts of the deposit. It was first described as interstitial anhedral aggregates up to 0.5 mm in size between carbonate grains and smaller isometric crystals in realgar or Pb-Tl-bearing sulfosalts (Sazonov et al., 1991a). Routhierite was confirmed by optical properties, including reflectance spectra, microhardness, chemical composition, PXRD pattern and refined parameters of the unit cell. It contains Zn (up to 1 wt. %), Ag (up to 0.3 wt. %) and Sb (4.3 wt. %). Murzin and Varla-mov (2010) provided additional chemical analyses including one analysis with a higher Sb content (up to 7.15wt.%).
In our samples, routhierite occurs in six assemblages, typically, as dissemination up to 0.5 x 0.5 cm in size in carbonates of breccias (Fig. 16f). The color
^ QI*
RM^r^i H
■ <- »
Cln
• " sic ;,,
Apt *
Prn ..
Tsg >' 1/
^ ùéÊT-"
fr y /
Til
* ' w™
Vik
/\ i "i
1?
Fig. 2d. Sulfosalts of the Vorontsovskoe deposit, part V:
a - ramdohrite inclusions in arsenopyrite enclosed in vesuvianite; b - rebulite crystals and grains in calcite and quartz in assemblage with realgar; c - rebulite grain with a vrbaite inclusion; d - Ag-rich routhierite intergrown with dalnegroite in clinochlore with baryte and pyrite; e - sicherite inclusion in prehnite with As-bearing fluorapatite, Mn-bearing clinochlore, and pyrite (light gray rounded grains); f - intergrowth of sinnerite with aktashite and realgar included in pyrite crystal (dark gray) and calcite (black); g - pseudomorphs of tsygankoite crystals after alabandite in assemblage with tilasite in dolomite and calcite; h - twinnite grains around pyrite; i - vikingite inclusions in pyrite; k - intergrowth of vorontsovite, ferrovorontsovite, chabournéite, parapierrotite, and cinnabar in calcite with native gold; 1 - aggregate of vrbaite with realgar and baryte in calcite; m-an unknown phase II (UK2) intergrown with boscardinite.
BSE images.
of the mineral varies from bright red to dark red and its luster is either metallic or adamantine. Routhierite is translucent in thin fragments. In reflected light,
routherite is light gray. It is distinctly anisotropic in gray and brownish tones; however, routhierite from assemblage no. 7 is characterized by very weak ani-
sotropy. Abundant internal reflections are bright red and especially strong in immersion. The parameters of the tetragonal unit cell of routhierite from assemblages nos. 1 and 5 are given in Table 3. Most grains contain only minor amount of Ag (up to0.06 apfu) and Zn (up to 0.16 apfu) (Table 5). The grains of Ag- and Zn-rich routhierite up to 80 pm in size intergrown with dalne-groite were found in assemblage no. 1 (Fig. 26d). The EMPA of these grains showed a wide substitution according to Ag ^ Cu and Zn ^ Hg schemes up to the compositions corresponding to other members of the routhierite group: arsiccioite (Ag > Cu and Hg > Zn) and stalderite (Cu > Ag and Zn > Hg) (Table 5, an. 5 and 107, respectively). Both arsiccioite and stalderite have previously been described at the Monte Arsic-cio mine in Tuscany, Italy (Biagioni et al., 2014) and Lengenbach quarry (Graeser et al., 1995), respectively. Our findings are the first in the Russian Federation and second in the world for each of these species.
Semseyite Pb9SbgS21 was determined in an aggregate of sulfantimonites and galena in a sample collected at off-balance ore stockpile no. 2. The mineral forms grains up to 70 pm in size, which are intergrown with galena (Fig. lli) at the contact with sphalerite and pyrite and is associated with boulangerite, hetero-morphite, and plagionite. Semseyite contains a minor amount of Se (Table 5). It is grayish white in reflected light, slightly darker than pyrite, but much lighter than sphalerite. Semseyite and galena have close reflectance values and look bright in the air, but, at the contact with galena, semseyite looks slightly greenish. In immersion, the difference between these minerals becomes more obvious: semseyite is much darker. Bireflectance is distinct. The effects of anisotropy are strong in both the air and immersion.
Sicherite TlAg2(As,Sb)3S6was identified by chemical composition in sample from assemblage no. 1 (Table 5). This extremely rare sulfosalt was found as a single grain 10^5 ^m in size in prehnite in assemblage with boscardinite-ecrinsite, chabourneite, para-pierrotite, pyrite, routhierite, sphalerite, weissbergite, baryte, Mn-rich clinochlore, and As-bearing fluorapatite (Fig. 26e). In reflected light, the mineral looks white. Sicherite was known only from the Lengenbach quarry (Graeser et al., 2001). Our finding is, therefore, the first in Russia and second in the world.
Sinnerite Cu6As4S9 was tentatively identified in a sample from assemblage no. 1 as a single grain 13 x 9 pm in size, which was intergrowth with aktashite and realgar in a pyrite crystal enclosed in calcite (Fig. 26f). Other minerals of this assemblage include the minerals
of the chabourneite-dalnegroite series, coloradoite, native gold, orpiment, routhierite, baryte, hyalophane, fluorapatite, and cerussite. In reflected light, sinnerite looks light gray, is indistinguishable from aktashite and significantly darker than host pyrite and lighter than realgar. This is relatively consistent with the reference reflectance values for all four minerals in white light: R = 29, 30, 54 and 19-21 % for sinnerite, aktashite, pyrite, and realgar, respectively (Chvileva et al., 1988). In spite of the tiny grain size, its chemical composition is perfectly recalculated to the formula of a typical sinnerite (Table 5). The analytical total is slightly lower due to the subtraction of a small admixture of pyrite from the matrix. In the Russian Federation, sinnerite has previously been identified in the Elbrus polymetal-lic deposit in Northern Caucasus at the contact with chalcopyrite and fahlores (Bezsmertnaya et al., 1973). Our finding is the first in the Urals.
Tsnigriite AggSbTe3S3 was identified in samples collected at off-balance ore stockpile no. 2 in calcite-dolomite-quartz aggregates with galena and sphalerite. Tsnigriite forms inclusions up to 30 pm in size in galena and is associated with benleonardite, geocronite, and hessite (Fig. lid). Its chemical composition is close to ideal (Table 5). In reflected light, tsnigriite looks light gray with a faint greenish blue tint in comparison with white galena. It is anisotropic in brownish and grayish tones. In Russia, it was previously described as single microinclusions in galena from gold-polymetallic ores of the Berezitovoe deposit in Amur oblast (Vakh etal., 2016, 2019).
Tsygankoite Mn8TlgHg2(Sb21Pb2Tl)S48 is a new mineral with a unique set of species-defining elements (Kasatkin et al., 2018b). It was named after Mikhail Vladimirovich Tsyganko (born 1979), an amateur mineralogist and collector from Severouralsk, a founder of the Mineralogical Museum «Shtufnoi Kabinet» («Mineral Cabinet») and one of the authors of this work. A number of rare minerals were found in samples collected by him. Tsygankoite occurs as lath-like elongated crystals up to 0.2 mm in size in gangue minerals of carbonate breccias (dolomite, calcite, clinochlore) enclosed in arsenopyrite, pyrite, orpiment, and realgar (Fig. 16g). It often forms partial pseudomorphs after alabandite (Fig. 26g) and intergrowths with routhierite and sphalerite.
Tsygankoite is opaque, has a black color and streak and a metallic luster; it is brittle, with an uneven fracture. No cleavage is observed. The Vickers microhard-ness (VHN, 10 g load) is 144 kg/mm2 corresponding to a Mohs hardness of ~3. The calculated density is
Fig. 27. Crystal structure of tsygankoite in projection onplane (010).
Yellow, blue, turquoise, red, lilac, and gray - atoms of S, Tl, Hg, Sb and (Sb,As), (Sb,Pb,Tl), and Mn, respectively. Thick orange lines - short strong Sb-S bonds, thin lines -longer distances. Other cation-anion bonds correspond to distances defining the complete coordination polyhedron. Axis c is vertical and slightly inclined.
5.450 g/cm-3. In reflected light, tsygankoite looks white at the contact with alabandite, routhierite, and sphalerite and light gray at the contact with pyrite and arse-nopyrite. Bireflectance is weak in the air and distinct in immersion from white to pale yellow. Tsygankoite is strongly anisotropic in grayish white and pinkish gray tones; rare internal reflections are light gray. The reflectance spectra are shown in Fig. 12. The reflectance values for the wavelengths recommended by the Commission on Ore Mineralogy of the IMA are as follows (R JR , %): 31.9/33.1 (470 nm), 31.2/32.4
v min max' ' v ''
(546 nm), 30.2/31.6 (589 nm), 28.7/29.8 (650 nm). The chemical composition of the holotype is given in the Table 5. Its empirical formula based on the sum of all atoms of 90 is Mn8 06Tl8 00Hgj 90(Sb17 87As319Pbj 99 Tl ) S
0.97'24.02 48.03'
Tsygankoite is monoclinic, space group C2/m, Z = 1. The unit cell parameters are given in Table 3. The strongest reflections of its PXRD pattern are as follows [d, A (I, %) (hkl)\. 3.587(100)(112), 3.353(70) (-114), 3.204(88)(405), 2.841(72)(-513), 2.786(99) (-514). The crystal structure of tsygankoite contains 11 independent cation sites (four of which are mixed
sites that were refined with one set of coordinates each) and 12 different sulfur sites (Fig. 27). It consists of an alternation of two thick layer-like arrays based on PbS-and SnS-archetypes, respectively. Both are typical of sulfosalt structures. The array based on the PbS-arche-type (i.e., with a PbS-like topology) contains a Hg site with a typical bond scheme, a Tl site, an octahedrally coordinated Mn1 site, and two Sb sites labeled Sb1 and Sb2. The alternating array based on the SnS-archetype (an array with a more pronounced steric role of lone electron pairs) with a general bond scheme represented by that observed in SnS [10] contains four distinct Sb sites, all of which are statistically mixed either with heavier cations (refined as Pb or Tl component) or As. A Tl site (refined as «T13») is embedded in this array and a Mn2+ site is apical to the second array. Close spatial relationship of large Tl+ and small Mn2+ polyhedra in the former array and along of its contact with the latter array is of interest.
Twinnite PbnoTlniSb,,AsnoS was noted in the
U.o U.l l.j U.o 4
realgar-bearing ores as dissemination of anhedral grains and intergrowths with aktashite (Vikentyev et al., 2016). Three chemical analyses given in this work, however, have higher totals (up to 105 wt. %) and correspond by stoichiometry to guettardite. The reliable twinnite was identified by us in assemblages nos. 1 and 5 as anhedral grains upto0.3 mm in size. In some cases, twinnite forms intergrowths with boscardinite around pyrite grains (Fig. 26h). It is also associated with aktashite, minerals of the boscardinite-ecrinsite series, chabourneite, native gold, orpiment, realgar, and routhierite. Twinnite is black, opaque with a metallic luster. Perfect cleavage is observed along {100}. In reflected light, twinnite is white, locally, with greenish or bluish tints. Bireflectance is distinct in the air and strong in immersion. Twinnite is moderately anisotropic without color effects. The chemical composition and parameters of the monoclinic unit cell of twinnite from both assemblages are given in Tables 5 and 3, respectively. Our finding of twinnite is the first in the Russian Federation.
Veenite Pb16Sb9xAs7+xS40 (where x~0.0-0.5) was identified only in one sample from assemblage no. 7. The mineral forms rare 30-pm inclusions in gangue minerals of breccia (calcite, dolomite, clinochlore) and is associated with pyrite, arsenopyrite, sphalerite, native arsenic and tsygankoite. In reflected light, veenite looks white. It is distinctly anisotropic in dark gray tones. The mineral contains high Tl amount (Table 5), which is typical of all members of the sartorite group (Topa et al., 2017b; Topa, Kolitsch, 2018). Vikentyev
et al. (2016) reported on two chemical compositions of «veenite with Cu and Hg» and only trace amount of As (0.38 and 0.18 wt. %). The refinement of the veenite crystal structure, however, shows that As is a species-defining element of this sulfosalt (Topa, Mako-vicky, 2017). The recalculations of analyses given by Vikentyev et al. (2016) better correspond to rouxelite Cu2HgPb22Sb28S64(O,S)2, however, this identification requires additional optical and XRD studies. In Russia, «veenite» was previously noted as gray tabular crystals in «carbonatites» of the Krestovozdvizhensky mine in the Southern Urals (Popov, Kolisnichenko, 2008). The high As and low Sb contents of the Southern Urals mineral, however, contradict its identification as veenite. Our finding is the first in the Russian Federation.
Vikingite Ag5Pb8Bi13S30 was tentatively identified in a sample mainly consisting of quartz, pyrite, galena, sphalerite, and chalcopyrite collected at off-balance ore stockpile no. 2. Vikingite forms rare small (up to 15 pm in size) inclusions in pyrite (Fig. 26i). Compared to the ideal formula of vikingite, our sulfosalt is Ag-deficient (Table 5), which is similar to some previously published compositions (Moelo et al., 1987). The optical properties of the mineral match those of vikingite: in reflected light, it looks grayish white and is slightly darker than the host pyrite; it is weakly anisotropic in grayish tones.
Vorontsovite (Hg5Cu)S6TlAs4S12 and ferrovoron-tsovite (Fe5Cu)S6TlAs4S12 are new minerals discovered at the deposit (Kasatkin et al., 2018a). Vorontsovite is named after its type locality, Vorontsovskoe deposit, and also indirectly honors a mining engineer Vladimir Vasil'evich Vorontsov (1842-after 1908), who was a superintendent of the Bogoslovskiy mining district and organized extensive geological survey and prospecting work that resulted in the discovery of an iron deposit. The nearby mining settlement of Vorontsovka and the Vorontsovskoe iron deposit were also named after him. The adjacent Vorontsovskoe gold deposit, which was discovered in 1985, was named after the settlement of Vorontsovka. Ferrovorontsovite is named for its chemical composition, as a Fe analogue of vorontsovite.
Vorontsovite and ferrovorontsovite occur in assemblage no. 2 as numerous anhedral grains up to 0.5 (vorontsovite) and 0.2 (ferrovorontsovite) mm in size in gangue minerals of breccias (calcite, dolomite, clinochlore) and as inclusions in orpiment, realgar, and stibnite (Fig. 16h). Both minerals are often inter-grown with each other, as well as with cinnabar, para-pierrotite, routhierite, and minerals of the chabourne-ite group and form polymineral aggregates up to 0.2
mm in size (Fig. 26k). In contrast to ferrovorontsovite, vorontsovite was also found in assemblage no. 1 as rare small (<10 pm) grains in calcite and baryte. Both minerals are opaque, black, with a dark red streak and a metallic luster. They are brittle, with uneven fracture. No cleavage is observed. The Vickers hardness (VHN, 10g load) is 172 kg/mm2 for vorontsovite and 170 kg/mm2 for ferrovorontsovite corresponding to a Mohs hardness of ~ 3^. The calculated density is 5.140 and 4.744 g/cm3, respectively.
In reflected light, both sulfosalts are light gray with a bluish tint; they are isotropic with abundant internal reflections, which are distinct in the air and strong in immersion (Kasatkin, Pautov, 2020). The color of internal reflections varies from dark red to bright red in vorontsovite and from dark red to dark brown in ferrovorontsovite. Their reflectance spectra are shown in Fig. 12. The reflectance values for the wavelengths recommended by the Commission on Ore Mineralogy of the IMA are as follows (R, %; vorontsovite /ferrovorontsovite): 24.9/26.2 (470 nm), 23.7/24.5 (546 nm), 22.8/23.9 (589 nm), 21.3/23.2 (650 nm).
The chemical composition of the holotype samples of both minerals is given in Table 5. Their empirical formulas are recalculated on the basis of 23 atoms pfu:
[(H§3.02Fei.63Zn0.33)4.98(Cu0.91Ag0.10)1.0l](Tl0.96Cs0.04)1.00 (As3.62Sb0.33Te0.05)4.00S12.01 (v°r°nts°vite) and [(Fe274 H§1.94Zn0.27)4.95(Cu0.96Ag0.06)1.02](Tl0.98Cs0.05)1.03(As3.68
Sb027Te005)400S1200 (ferrovorontsovite). Both minerals are cubic, space group I-43m,Z= 2. The parameters of their unit cells are given in Table 3. The strongest reflections of the PXRD patterns are [d, A (I, %) (hkl); voront-sovite/ferrovorontsovite]: 4.198(79)/4.175(93)(211), 2.970(100)/2.952(100)(222), 2.749(66)/2.735(57) (321), 1.818(49)/1.810(40)(440), 1.550(31)/1.543(24) (622).
Vorontsovite and ferrovorontsovite are Tl and Tl-Fe analogs of galkhaite (Hg5Cu)S6CsAs4S12, respectively. All three minerals form the galkhaite group. Similarly to galkhaite, the crystal structure of voron-tsovite and ferrovorontsovite is characterized by three independent crystallographic sites (Fig. 28). The first site is occupied by metal atoms in tetrahedral coordination: Hg (dominant in vorontsovite and galkhaite), Fe (dominant in ferrovorontsovite), Zn, Cu, and Ag. The second site is a 12-fold coordinated site occupied by Tl atoms (Cs atoms in galkhaite) centering Laves polyhedra TlS12 (CsS12 in galkhaite). The third site is a trigonal pyramid with As coordinating three S. Our EMPA results show an isomorphic substitution in each of three crystallographic sites. The largest degree of
Mt
,HB I Hg
He
Hg
Ha-
ns
He
HS
_.
J / \ a 0.6 -
H, a.
/ vJJ.
/ r/\ i w <J 0.4 ■
Hi
¿-7 0.2 -
Fig. 28. Crystal structure of vorontsovite/ ferrovorontsovite along [001].
For simplicity, the site occupied by (Hg, Fe, Zn, Cu, Ag), (Tl, Cs), and (As, Sb) are indicated as Hg, Tl, and As, respectively.
Fig. 29. Hg : Fe : Zn ratios for tetrahedral sites in vorontsovite and ferrovorontsovite.
1 - vorontsovite; 2 - vorontsovite holotype; 3 -ferrovorontsovite; 4 - ferrovorontsovite holotype.
substitution is recorded in tetrahedral sites following a Hg ^ Fe scheme that leads to a continuous solid solution series extending from Fe-free vorontsovite to Hg-firee ferrovorontsovite. The compositions corresponding to vorontsovite and ferrovorontsovite were determined in 89 and 77 analyses, respectively (Fig. 29). The Zn content does not exceed 1.4 wt. % (0.34 apfu) in vorontsovite and 1.4 wt. % (0.33 apfu) in ferrovo-
Tl (apfu)
Fig. 30. Tl-Cs correlation in minerals of the galkhaite group.
1 - ferrovorontsovite; 2 - vorontsovite; 3 - galkhaite.
rontsovite. The substitution of As for Sb in the third site is limited that is similar to the 12-fold coordinated site with Tl-Cs substitution, where the maximum Cs content was only 0.7 wt. % (0.09 apfu) in vorontsovite and 0.8 wt. % (0.08 apfu) in ferrovorontsovite (Kasat-kin etal., 2018a).
At off-balance ore stockpile no. 2, we later collected carbonate breccias with numerous inclusions of vo-rontsovite and ferrovorontsovite, which are characterized by significantly higher Cs content (Fig. 30). One of Cs-rich vorontsovite contained zones with Cs > Tl, which formally correspond to galkhaite (Table 5; Fig. 30). This is the first mineral with species-defining Cs found at the Vorontsovskoe deposit and the second finding of galkhaite in the Russian Federation after the Gal-Khaya deposit in Yakutia (Gruzdev et al., 1972). The highest Cs content in ferrovorontsovite reaches 0.38 apfu.
Vrbaite HgTlAs SbSon was identified in as-
4 8 2 2U
semblages nos. 1 and 3 as anhedral intergrowths with realgar and baryte up to 0.2 mm in size, which are enclosed in carbonates, and small inclusions in rebulite (Figs. 26c, 261). The mineral is orange-red, transparent in thin sections and has a metallic luster. In reflected light, vrbaite is grayish white; bireflectance is weak in the air and noticeable in immersion. It is distinctly anisotropic with faded color effects. Abundant orange-red internal reflections are especially strong in immersion. The chemical composition of vrbaite is stoichiomet-ric (Table 5). The parameters of the orthorhombic unit cell are given in Table 3. Similarly to lorandite, vrbaite was mentioned in a list of minerals associated with
lermontovite from the Beshtau U deposit in Northern Caucasus without analytical data (Melkov et al., 1983). We consider our finding the first one in the Russian Federation.
Weissbergite TlSbS2 was found in assemblage no. 1, where it forms elongated grains up to 50 pm in size in carbonates, inclusions in arsenopyrite, thin rims around realgar aggregates and intimate intergrowths with pokhodyashinite (Fig. 21h). It is also associated with aktashite, bernardite, boscardinite, chabournéite, dalnegroite, native gold, parapierrotite, pyrite, and routhierite. In reflected light, weissbergite is grayish white and looks gray at the contact with arsenopyrite. Bireflectance is weak in the air and noticeable in immersion from white to light gray. The mineral is strongly anisotropic in bluish, brownish, and beige tones. Rare orange-red internal reflections are weak in the air and distinct in immersion. Chemically, most grains correspond to the end-member TlSbS2 (Table 5, an. 120); however, some grains contain As (Table 5, an. 121). The compositions, where As exceeds 1 apfu (calculated for S = 8), correspond to the field of isostructural drechslerite Tl4(Sb4-x Asx)S8, which was recently approved and occupies an intermediate position in the weissbergite-lorándite system (Topa et al., 2019). Optically, drechslerite and weissbergite are similar, but the former has more noticeable bireflectance in the air. The identification of weissbergite was supported by SXRD data (Table 3). Our findings of both sulfosalts are the first in the Russian Federation.
Zinkenite Pb9Sb22S42 was described as acicular crystals or anhedral aggregates up to 0.2-0.3 mm across in carbonate breccias (Sazonov et al., 1991a). It intergrows with stibnite, fills microfractures in arsenopyrite and contains realgar inclusions. The mineral was identified by its chemical composition and optical properties. Later, zinkenite was found as anhedral grains and acicular crystals less than 1 mm in size and fibrous aggregates up to 2 cm in size in marblized limestones (Vikentyev et al., 2016). Locally, it contains As up to 7.6 wt. %.
A sample with zinkenite from the Vorontsovskoe deposit in our collection corresponds to the above description and, most likely, originates from the same mineral assemblage (Fig. 16i). The chemical composition of zinkenite from this sample and its hexagonal unit-cell parameters are given in Tables 5 and 3, respectively. The As-bearing zinkenite was also found in assemblage no. 1, where it occurs as rounded grains up to 0.2 mm in size in carbonates, and assemblage no. 4 (Table 5), where it forms acicular crystals up to
1 mm size in quartz-carbonate rock, oval inclusions up to 0.1 mm in size in realgar and native arsenic and small intergrowths with coloradoite and pyrite. In assemblage no. 1, zinkenite is associated with aktashite, boscardinite, chabournéite, écrinsite, hutchinsonite, orpiment, parapierrotite, pyrite, routhierite, stibnite, magnetite, baryte, etc. In assemblage no. 4, zinkenite is observed with aktashite, andorite, cinnabar, routhierite, Hg-bearing sphalerite, and tennantite-(Zn). In reflected light, zinkenite is white and its bireflectance and anisotropy are distinct, especially, in immersion. Red internal reflections are observed.
Some analyses of sulfosalts cannot be recalculated to certain minerals, e.g., phases of compositions Mn-Ag-Pb-Tl-As-Sb-S and MnPbAg2Sb4As2S12.
Phase I of the Mn-Ag-Pb-Tl-As-Sb-S c omposi-tion (Table 5) was found in assemblages nos. 1 and 2. In assemblage no. 1, the mineral occurs as intergrowths with aktashite and grains at the contact of aktashite and Mn-Hg-bearing sphalerite. The maximum size of grains is 0.18 x 0.1 mm (Fig. 11a). In assemblage no. 2, this phase composes small inclusions (up to 10 pm) in realgar and carbonate aggregates. It is possible that phase Iisa Mn-Ag-bearing variety of écrinsite.
Phase II of the approximate composition MnPbAg2Sb4As2S12 (Table 5) was identified in assemblages nos. 1 and 5 in form of 100-pm inter-growths with boscardinite and isometric grains up to 20 pm in size in pyrite (Fig. 26m). It is opaque, has a black color and a metallic luster. In reflected light, this phase is white; the bireflectance is very weak; it is strongly anisotropic in light gray and pinkish-brownish tones. No internal reflections are observed. The reflectance values for the wavelengths recommended by the Commission on Ore Mineralogy of the IMA are as follows (R IR , %): 33.8/34.4 (470 nm), 32.8/33.6
v min max' ' v ' '
(546 nm), 32.0/32.9 (589 nm), 30.5/31.5 (650 nm). In terms of the chemical composition and stoichiometry, phase II is similar to oyonite, but contains almost half less ofPb.
Oxyhalides
Bismoclite BiOCl was detected in assemblage no. 4 as tiny (<10 pm) rare inclusions in calcite-preh-nite-diopside rock in assemblage with chabourné-
ite, native gold, parapierrotite, pyrite, and realgar. Its chemical composition is as follows (wt. %, average of 3 analyses): 88.72 Bi2O3, 12.99 CI, 2.94 -O = Cl2 (total 98.77). The empirical formula based on two anions is
Bi1.01O1.03Cl0.97'
Oxides and hydroxides
Akhtenskite MnO2 was identified in samples from the dumps of the southern open pit in form of black sparkling plates up to 0.5 mm in size, composing a zone of ~1 x 1 cm in massive brown limonite and dull black goethite with quartz (Fig. 31a). According to EMPA, the mineral contains only Mn and O. The strongest reflections of the PXRD pattern are as follows [d, A (I)]: 2.41(70), 2.10(30), 1.63(100), 1.43(40), 1.07(10). The calculated parameters of the hexagonal unit cell correspond to akhtenskite (Table 3).
Arsenolite As2O3 was mentioned in the oxidation products of massive dark gray nodules and veinlets of native arsenic up to 2-3 cm thick in an aggregate of layered silicate and as fine dissemination in breccias (Vikentyev et al., 2016). Arsenolite and its dimorph claudetite were also identified in samples from the dumps of the northern open pit (Kasatkin, 2019). Both minerals are intergrown with each other and form grayish white powdery aggregates replacing native arsenic from assemblage no. 6 with arsenopyrite, native gold, orpiment, calcite, quartz, muscovite-2M1 and Cl-bearing fluorapatite (Figs. 7b, 7d, 31b). According to EMPA, the minerals contain only As and O. The PXRD data of a sample with both oxides are given in Table 6. The calculated parameters of the unit cells of arsenolite and claudetite are given in Table 3. This is the first finding of claudetite in the Russian Federation.
Asbolane Mn4+(0,0H)2- (Co,Ni,Mg,Ca)x(OH)2x-nH2O was found in samples of the oxidation zone collected in the dumps of southern open pit. It occurs as black sooty grains up to 1 mm in size in calcite and quartz with nontronite (Fig. 31c). The mineral contains up to 2.5 wt. % Co and 12.6 wt. % Cu, as well as traces of Al, Si, V, Fe, and Zn. The strong reflections of the PXRD pattern are as follows: [d, A (I)]: 9.66(100), 4.80(100), 2.42(40), 2.39(20), 1.92(10), 1.53(50), 1.43(50). The calculated parameters of the hexagonal unit cell are given in Table 3.
Birnessite (Na,Ca,K)06(Mn4+,Mn3+)2O4 • 1.5H2O was identified in samples from the dumps of the southern open pit in dark brown soft crusts composed of kaolinite (-80 vol. %), quartz, and supergene Mn oxides (birnessite, vernadite). These crusts overgrow black goethite pseudomorphs after a large pyrite crystal (Fig. 31d). Birnessite was identified according to a strong predominance of Mn and subordinate amounts of Na > K > Ca in chemical analysis and PXRD pattern with the following reflections: [d, A]: 7.13(vs), 3.55(s),
2.53, 2.43, 2.14, 1.82, 1.46. The calculated parameters of the monoclinic unit cell are given in Table 3.
Bixbyite Mn3+2O3 was found in samples from the dumps of the southern open pit. It occurs in dark brown to black powdery aggregates composed of kaolinite and Mn oxides (bixbyite, vernadite) in assemblage with cryptomelane, calcite, and quartz. The Mn/Fe ratio of the mineral is close to 2 : 1; it also exhibits traces of Ti and Ca. The strongest reflections of the PXRD pattern ([2.69 (vs), 1.65 (s), 3.85, 2.34, 1.99, 1.80, 1.45, 1.40, 1.29 A]) and the calculated parameters of the cubic unit cell correspond to bixbyite (Table 3).
Cesarolite PbMn4+3O6(OH)2 forms dark earthy brown aggregates that overgrow hemimorphite crystals in samples collected at the dumps of the southern open pit (Fig. 31e). The chemical composition of the mineral is as follows (wt. %, average of five analyses; H20 calculated by stoichiometry): 45.55 PbO, 4.25 Fe2O3, 46.07 Mn02, 3.45 H20 (total 99.32). The empirical formula based on eight O atoms, two of which are assigned to hydroxyl groups, is Pb106(Mn4+276 Fe3+028)S304O6(OH)2. The strongest reflections of the PXRD pattern ([(d, A (I, %)): 3.41(40), 2.21(100), 2.11(50), 1.88(20), 1.77(40), 1.58(50), 1.49(10), 1.42(20)]) and the calculated parameters of the hexagonal unit cell correspond to cesarolite (Table 3).
Minerals of the chromite-magnesiochromite series are rare in metasomatites after carbonate breccias. Chromite and magnesiochromite were found in assemblage no.l, where they form anhedral grains up to 0.15 mm in size in armenite, augite, and prehnite. Their chemical composition varies and some grains are characterized by both compositions. The associated minerals with chromite and magnesiochromite include realgar, pyrite, aktashite, arsenic, arsenopyrite, colora-doite, native gold, and weissbergite. The chemical composition of chromite/magnesiochromite is as follows (wt. %, average of three analyses for each mineral; Fe2+/Fe3+ ratio is calculated from the charge balance): 9.45/10.89 MgO, 18.45/16.65 FeO, 5.35/6.29 Al2O3, 61.97/61.72 Cr2O3, 5.14/4.94 Fe2O3 (total 100.36/100.49). The empirical formulas on the basis of four O atoms and three metal cations are
(Fe2+0.52Mg0.48)S1.00(Cri.66A^^l0.21Fe3+0.13)S2.00O4 (Mg0.54
Fe2+0.46)S1.00(Cri.63Al0.25Fe3+0.12)S2.00O4'reSPeCtlVely-
Minerals of the coronadite group of the hol-landite supergroup locally occur in the oxidation
zone of the Vorontsovskoe deposit. Samples from the dumps of the southern open pit contain four members of this group: coronadite, cryptomelane, hollandite, and manjiroite. Coronadite Pb(Mn4+6Mn3+2)O16 forms
Fig. 31. Oxides and hydroxides of the Vorontsovskoe deposit, part I:
a - black shiny akhtenskite plates on black dull goethite and orange limonite; b - grayish white powdery aggregates composed of arsenolite and claudetite on native arsenic; c - black sooty grains of Co-Cu-bearing asbolane in calcite with yellow nontronite; d - dark brown crust composed of birnessite, vernadite, kaolinite, and quartz on goethite pseudomorph after pyrite; e - dark brown earthy cesàrolite crusts on colorless radial hemimorphite aggregates; f - black dendrites on calcite; g - black cryptomelane spherulites on quartz; h - dark red massive hematite with black crust (in the bottom) of hollandite and lithiophorite; i - black crusts of manjiroite (with microinclusions of rutile) on quartz.
Collections: A.V Kasatkin (a-f, h, i), Museum «Shtufnoi Kabinet», Severouralsk (g). Photo: A.D. Kasatkina (a-f, h, i), M.V. Tsyganko (g).
black dendrites up to 4 cm long on quartz with cal-cite and fine-grained pyrite (Fig. 31f). Cryptomelane K(Mn4+7Mn3+)O16 composes spectacular dark brown to black spherulites up to 1 cm in diameter on oxidized quartz (Fig. 31g). Hollandite Ba(Mn4+6Mn3+2)O16 in-tergrown with lithiophorite occurs as black opaque fine-grained crusts up to 3 * 1 cm on dark red hematite (Fig. 31h). Manjiroite Na(Mn4+7Mn3+)O16 forms dull black crusts on quartz (Fig. 31i) and contains rutile microinclusions. The chemical composition of minerals of the coronadite group is given in Table 7. The strongest reflections in the PXRD patterns are [d, Â
(I)] 6.90(40), 3.47(40), 3.12(100), 2.40(80), 2.20(40), 2.12(20), 1.86(10), 1.56(10) for coronadite; 6.93(90), 4.90(50), 3.11(70), 2.39(100), 2.16(40), 1.83(40), 1.54(40), 1.42(20) for cryptomelane; 3.13(s), 2.38(s), 6.96, 3.47, 2.16, 1.87, 1.81, 1.60, 1.55 for hollandite and 6.96(90), 4.91(70), 3.48(30), 3.12(100), 2.40(100), 2.15(40), 1.83(40), 1.55(40) for manjiroite. The parameters of the tetragonal unit cells of all four minerals are given in Table 3.
Ferberite Fe2+(W04) was found as rare short-prismatic crystals up to 20 x 15 pm in size in quartz with calcite and muscovite in assemblage no. 4. It
Table 6
Powder XRD data of sample 1810K with claudetite and arsenolite
d, Â (/, %) sample 1810K Claudetite Arsenolite Quartz Muscovite-2M1
[JCPDS-ICDD, [JCPDS-ICDD, [JCPDS-ICDD, [JCPDS-ICDD, 06-
15-0778] 36-1490] 46-1045] 0263]
10.01(30) 9.95(95)
6.37(50) 6.496(10) 6.3993(44)
4.98(15) 4.924(25) 4.97(30)
4.45(20) 4.47(20)
4.24(25) 4.277(4) 4.2549(16)
3.86(10) 3.88(14)
3.70(10) 3.717(2) 3.73(18)
3.47(15) 3.454(50) 3.48(20)
3.33(100) 3.356(20), 3.328(18) 3.3410(2) 3.3434(100) 3.34(25), 3.32(100)
3.24(25) 3.245(100)
3.18(50) 3.1993(100) 3.19(30)
2.98(15) 2.987(35)
2.85(10) 2.859(25)
2.76(15) 2.771(35) 2.7698(26) 2.789(20)
2.66(8) 2.640(16)
2.55(40) 2.5422(34) 2.566(55)
2.44(10) 2.4568(9) 2.450(8)
2.40(10) 2.398(10)
2.25(12) 2.264(25), 2.253(6) 2.2619(6) 2.2814(8), 2.2361(4) 2.254(10)
2.12(15) 2.104(6) 2.1327(12) 2.1277(6) 2.132(20)
1.98(15) 1.9798(4) 1.993(45)
1.95(25) 1.9587(22) 1.951(6)
1.87(5) 1.857(12) 1.8728(4) 1.871(4)
1.81(30) 1.8179(13)
1.66(25) 1.6477(4) 1.6701(14) 1.6717(4), 1.6591(2) 1.662(12)
1.60(8) 1.5988(2) 1.5990(5) 1.603(6)
1.54(20) 1.5515(14) 1.5415(9) 1.541(4)
1.50(12) 1.504(30)
1.44(8) 1.4422(7) 1.4528(2) 1.453(4)
Table 7
Chemical composition (wt. %) of minerals of the coronadite group from assemblage no. 9
An. no. Mineral K2O CaO BaO M«2°3 Fe2°3 Mn°2 Total Formula
1 Coronadite 0.20 0.76 - 12.30 4.79 60.38 99.36 Pb„,2Ca0,2K0,4(Mn4+6.10Mn3+L37Fe3+a53)8°16
2 Cryptomelane 5.02 0.64 1.49 10.90 - 81.20 100.10 ^0.79Ca0.08Ba0.07(Mn4+6.90Mn3+1.02V3+0.0s)8O16
3 Hollandite - 0.14 18.88 17.30 2.58 60.45 99.35 Ba1,4Ca0,2(Mn4+,88Mn3+L85Fe3+a27)8°16
4 Manjiroite 0.88 - - 8.89 1.58 86.64 101.59 Na082K013(Mn4+706Mn3+080Fe3+014)8O16
Note. The Mn4+/Mn3+ ratio is calculated from charge balance. The analyses contain (wt. %): 20.93 PbO (an. 1), 0.85 V2O3 (an. 2), 3.60 Na20 (an. 4). Samples: 1721K - an. 1; 1808K - an. 2; 1214G - an. 3; 1316M - an. 4.
occurs together with native arsenic, baryte, cinnabar, coloradoite, fluorapatite, orpiment, parapierrotite, pyrite, realgar, sphalerite, and stibnite. In reflected light, ferberite has a grayish white color in comparison with hosting quartz. Bireflectance is weak and anisotropy is distinct. Rare dark brown-red internal reflections are
observed in immersion. In chemical composition, ferberite contains a low amount of a hubnerite component (wt. %, average of three analyses): 2.31 MnO, 21.15 FeO, 75.98 W03 (total 99.44). The empirical formula on the basis of four O atoms is (Fe0 90Mn010)S100Wj 00O4.
Fergusonite-(Y) YNbO4 was tentatively identified in a sample collected from the main ore stockpile of the deposit. The mineral occurs as rare small (<7 pm) inclusions in dolomite-calcite rock and is associated with baryte, hingganite-(Y), hingganite-(Nd), Cr-bearing magnetite, pyrite, realgar, routhierite, and wakabayashilite. The chemical composition of the mineral is as follows (wt. %, average of three analyses): 0.40 CaO, 27.13 Y2O3, 0.57 Ce2O3, 1.61 Nd2O3, 1.56 Sm2O3, 4.03 Gd203, 0.57 Tb2O3, 4.70 Dy^, 3.44 Er2O3, 0.71 Tm2O3, 2.57 Yb2O3, 0.39 Lu^, 0.48 Ti02, 0.78 Th02, 4-7.63 Nb2O5, 0.56 Ta2O5, 2.32 W03 (total 99.45). The empirical formula on the basis of four O atoms is (y0 65 Dy007Gd006Er0 05Yb004Nd003Sm002
Ce0.01Tb0.01Tm0.01Lu0.01 Ca0.02Th0.01)S0.99(Nb0.97^^0.03Ti0.02
Ta001)sl03O4. In addition to fergusonite-(Y), we found in ore breccias of the deposit four minerals with species-defining REEs: gasparite-(La), chernovite-(Y), hingganite-(Y), and hingganite-(Nd). The ore breccias of the deposit are enriched in REEs and HREEs are dominant over LREEs (Murzin et al., 2010; Stepanov et al., 2017). The total REE content varies from 3.7 to 54.8 ppm increasing in more brecciated rocks.
Geikielite MgTiO3 and pyrophanite Mn2+TiO3 from the ilmenite group were found in assemblage no. 7. They form rare anhedral grains up to 30 pm in calcite-dolomite-clinochlore rock, which contain zones corresponding to both minerals in chemical composition (Mg-richest geikielite/Mn-richest pyrophanite, wt. %, average of three analyses for each mineral): 16.77/11.38 MgO, 23.08/30.71 MnO, 59.88/57.81 TiO2 (total 99.73/99.90). The empirical formulas on the basis of three O atoms are Mgn 5CMn„ Ti, JO, and
c?0.56 0.44 1.00 3
Mno.6oMgo.39Tii.oi°3'resPectively-
Goethite FeO(OH) was identified in several po-
lymineralic samples by strong reflections of the PXRD pattern (Sazonov et al., 1991a). In addition to its hydrated variety, goethite is a main component of the oxidation zone. In our samples from the dumps of the southern open pit, goethite occurs as fine-grained, botryoidal, and stalagmite-like aggregates of black to brown color (Figs. 32a, 32b) and pseudomorphs after pyrite. Black botryoidal goethite was studied by EMPA and XRD. It contains only Fe and O in chemical composition. According to the PXRD pattern, the mineral correspond to goethite. Its unit cell parameters are given in Table 3.
Hematite Fe2O3 occurs at the flanks of stringer-disseminated gold mineralization zones (Sazonov et al., 1991a). In altered skarns, it replaces magnetite and, rarely, forms lamellar aggregates in calcite. It was de-
termined by PXRD data. Abundant hematite was identified in assemblage no. 9. Its dark red aggregates are locally covered by black crusts composed of hollandite and lithiophorite (Fig. 31h). It contains only Fe and O in chemical composition. Its PXRD pattern belongs to hematite. The unit-cell parameters are given in Table 3.
Lithiophorite (Al,Li)(Mn4+,Mn3+)O2(OH)2 was found in samples from the dumps of the southern open pit. It composes black crusts together with hollandite on dark red massive hematite (Fig. 31h). The mineral was identified by its qualitative chemical composition (dominant Mn and O contents with subordinate Al amount) and PXRD pattern (strong reflections at 9.48 (vs), 4.75 (vs), 2.38 (s), 3.13, 2.47, 1.87, 1.55, 1.42 A; the calculated parameters of the hexagonal unit-cell are given in Table 3).
Magnetite Fe2+Fe3+2O4 in various quantities occurs in skarns. Magnetite and pyrite are exclusive ore minerals of unaltered skarns, where magnetite forms tiny (0.1-0.2 mm) isometric crystals or inclusions in pyrite. In metasomatites, the amount of magnetite does not exceed hundredth part of a percent (Sazonov et al., 1991a). In magnetite-sulfide ores of the calcite-garnet-epidote skarns at the southern flank of the deposit, magnetite composes euhedral iron black grains up to 0.5 cm in size and massive aggregates. They contain abundant dissemination of major arsenopyrite and pyrite, subordinate sphalerite, chalcopyrite, and galena and rare microinclusions of Bi-Te-bearing sulfides and sulfosalts (assemblage no. 8). Magnetite contains only Fe and O in chemical composition. According to the PXRD pattern, the mineral corresponds to magnetite; the refined parameter of its cubic unit cell is given in Table 3.
Manganite Mn3+0(0H) was identified in a sample collected from the dumps of the southern open pit. It occurs as fine-grained particles in crusts and spheru-lites of kutnohorite and is responsible for its dark gray color (Fig. 33b). Manganite contains only Mn and O in chemical composition. The strongest reflections of the PXRD pattern [3.40 (s), 2.63, 2.41, 1.80, 1.67 A] and the refined parameters of the monoclinic unit cell are consistent with manganite (Table 3).
Pyrolusite MnO2 was found in samples collected at the main ore stockpile and dumps of the northern open pit. It occurs as black columnar crystals up to 5 mm in size with a strong metallic luster, which are grouped into radial aggregates that fill veinlets up to 3-4 cm thick and 10 cm long. (Fig. 32c). Pyrolusite contains only Mn and O in chemical composition. The parameters of the tetragonal unit cell correspond to pyrolusite (Table 3).
Fig. 32. Oxides and hydroxides of the Vorontsovskoe deposit, part II:
a - stalagmite-like goethite; b - dark brown to black botryoidal goethite on massive limonite; c - black sparkling pyrolusite crystals in dark gray massive pyrolusite aggregate; d - pale grayish violet bunch-shaped chalcedony crusts in of massive quartz; e - crust of quartz crystals; f - black shiny ramsdellite crystals on brown-black massive goethite crust; g - black todorokite dendrites on quartz-calcite aggregate; h - black romanèchite crust on brown calcite and romanèchite aggregates; i - dark brown to black powdery crust composed of vernadite, kaolinite, and halloysite-7Â on quartz-carbonate matrix.
Collections: Museum «Shtufnoi Kabinet», Severouralsk (a, e), A.V. Kasatkin (b-d, f-i). Photo: M.V. Tsyganko (a, e), A.D. Kasatkina (b-d, f-i).
Quartz SiO2 is one of the major gangue minerals of the Vorontsovskoe deposit, however, its content varies. In metasomatites, milky white translucent quartz composes veins with poor sulfide (pyrite and chalco-pyrite) mineralization. Quartz occurs as small anhedral grains up to hundredth part of a millimeter in assemblage with chlorites, micas, carbonates, albite, and K-feldspar. Quartz is one of the major minerals (up to 90 vol. %) of the weathering mantle (Sazonov et al., 1991a). In the oxidation zone, abundant fine-grained quartz forms aggregates up to 3-5 mm in size with
a grain size of 0.01-0.05 mm. The quartz aggregates are enclosed in clay minerals and are often brown because of the presence of Fe oxides and hydroxides (Ka-banov, 2001). Quartz metasomatites (jasperoids) occur in limestones and at the contacts of dikes with limestones. Quartz forms fine-grained and chalcedony-like aggregates and rice-like crystals with hexagonal sections. In some areas, the granoblastic quartz aggregates replace limestone breccias up to 80 vol. % and form veins up to 7.5 m thick along the dike contacts (Vi-kentyev et al., 2016). In our samples, abundant quartz
was found in assemblage nos. 2, 4, and, especially, nos. 1 and 6, where it is one ofthe breccia-forming minerals together with calcite and dolomite. Quartz is abundant in assemblage no. 9 of the oxidation zone. Striking samples of pale grayish violet bunchy chalcedony were collected from the dumps of the southern open pit (Fig. 32d), as well as large (up to 30 cm) geodes and druses of dull white quartz crystals up to 1.5 cm in size (Fig. 32e).
Ramsdellite MnO2 was found in samples from the dumps of the southern open pit as black, highly lustrous lenticular crystals up to 0.5 mm in size, which are localized in areas up to 1 cm2 on a brownish black radial fibrous goethite crust (Fig. 32f). The mineral contains only Mn and О in chemical composition. The parameters of its orthorhombic unit cell correspond to ramsdellite (Table 3). Our finding is most probably the first in the Russian Federation.
Rancieite (Ca,Mn2+)02(Mn4+,Mn3+)O2 • 0.6H2O intergrown with todorokite (Na,Ca,K,Ba,Sr)1-x (Mn,Mg,Al)6O12 • 3-4H2O were identified in samples from the dumps of the southern open pit. Both minerals are present in subordinate amounts in a massive brown kaolinite-calcite aggregate. The minerals contain the dominant Mn, subordinate Ca, and minor Na. In the PXRD pattern of a mineral mixture, rancieite is characterized by reflections at d =7.51 (vs), 3.75 (s), 2.48, 2.07, and 1.42 A and todorokite exhibits reflections at 9.55 (vs), 4.81 (m), 2.44 (s), 2.35 (s), and 1.90 A. The calculated unit cell parameters of both oxides are given in Table 3. Samples with todorokite were also found at off-balance ore stockpile no. 2. The mineral composes black dendrites up to 3 cm long on quartz-calcite aggregates (Fig. 32g) and is associated with diopside, fluorapatite, pyrite, and talc. Its identification is based on a qualitative chemical analysis (strongly dominant Mn content with subordinate Ca, Mg, Na, and К contents) and a PXRD pattern (reflections at 9.66, 4.82, 3.06,2.48, and 1.90 A).
Romanechite (Ba,H2O)2(Mn4+,Mn3+)5O10 was found in samples collected in the dumps of the sou-them open pit. It forms dark gray to black opaque finegrained crusts up to 3 x l cm in size on calcite (Fig. 32h). The identification is supported by a qualitative chemical analysis (the presence of Ba, Mn, and O) and PXRD data (strong reflections at [d, A (I)]: 9.66(30), 6.96(50), 5.58(40), 3.48(60), 3.29(60), 2.89(50), 2.40 (100), 2.18(80); the calculated parameters of the mon-oclinic unit cell are given in Table 3).
Rutile TiO2 is rare and occurs in carbonate-talc matrix of breccias; it contains up to 0.75 wt. % W03
(Murzin, Varlamov, 2010). It is occasional among the gangue minerals of assemblages nos. 1, 4, and 6 and also occurs as microinclusions in manjiroite in assemblage no. 9. Rutile was identified by chemical composition (the presence of Ti and O) and reflections at 3.25, 2.49, and 1.69 A in the PXRD patterns of mineral mixtures.
Vernadite (Mn,Fe,Ca,Na)(0,0H)2 • nH2O is an abundant accessory mineral of karst areas, where its content reaches several percents (Sazonov et al., 1991a). In samples from the dumps of the southern open pit, vernadite was found as monomineral dark brown crusts and in brown-black polymineral powdery aggregates, which are composed of clay minerals (kaolinite, dickite, halloysite), carbonates (calcite, rhodochrosite), fine-grained quartz and other supergene Mn oxides (birnessite, bixbyite, cryptomelane, todorokite) (Figs. 31d, 32i). Vernadite was identified by qualitative chemical composition (the presence of strongly dominant Mn and subordinate amounts of Fe, K, and Ca) and XRD data (characteristic broad reflections with d = 2.41 and 1.41 A).
Carbonates
Azurite Cu3(CO3)2(OH)2 was found in several samples from the dumps of the southern open pit as dark blue grains up to 5 mm in size and thin coatings on oxidized quartz in assemblage with bayldonite, hemimorphite, malachite, galena, pyrite, sphalerite, and tennantite-(Zn) (Fig. 33i). Azurite was identified by qualitative chemical composition (the presence of Cu in cationic composition) and XRD data (Table 3).
Calcite CaCO3 is a major gangue carbonate of the Vorontsovskoe deposit. It is ubiquitous in limestones, marbles, carbonate-bearing tuffites, eruptive breccias (limestone fragments, volcanic matrix) and occurs in post-ore assemblages of skarns. Similarly to dolomite, calcite is abundant in wollastonite skarns, beresites, listvenites, and jasperoids. Spectacular druses of the colorless scalenohedral calcite crystals up to 3 cm in size were collected from the dumps of the southern open pit (Fig. 33a). Calcite is described in details in many publications (Sazonov et al., 1991a; Murzin, Varlamov, 2010; Vikentyev et al., 2016; Stepanov et al., 2017; Soroka et al., 2017, 2018). Jasperoids contain Mg-, Mn- and Fe-bearing calcite (Sazonov et al., 1991a), whereas Mn-bearing calcite (up to 6.9 wt. % MnO) was reported from breccia matrix (Murzin, Varlamov, 2010). Mn-bearing calcite with up to 9.35 wt. % MnO was identified by us in assemblage no. 5.
Fig. 33. Carbonates, sulfates, phosphates and arsenates of the Vorontsovskoe deposit:
a - crust of colorless calcite crystals; b - grayish black kutnohorite spherules with fine-grained manganite; c - green malachite crusts on oxidized quartz aggregate; d - yellow powdery beaverite-(Cu) on quartz with malachite; e - green fine-grained brochantite aggregates on quartz with calcite; f - pale blue thin chalcanthite crusts on quartz with calcite and oxidized sulfides; g - dirty white powdery crusts composed of pentahydrite, starkeyite, and gypsum; h - zoned grains composed of minerals of the apatite group in calcite and clinochlore with pyrite (white): 1 - fluorapatite; 2 - hydroxylapatite; 3 - chlorapatite; 4 - turneaurite (numbers correspond to the analyses in Table 9); i - green crusts of bayldonite on quartz in assemblage with pale blue and white hemimorphite and bright blue azurite.
Collections: Museum «Shtufnoi Kabinet», Severouralsk (a, c), A.V. Kasatkin (b, d-i). Photo: M.V Tsyganko (a, c), A.D. Kasatkina (b, d-g, i), BSE image (h).
Cerussite Pb(C03) was found in samples from the southern open pit dumps as colorless crusts with adamantine luster uptol*0.5 mm in size, which replace galena in a quartz-sulfide aggregate from assemblage no. 9. Cerussite is associated with anglesite, pyrite, and sphalerite. The mineral was determined by EMPA, XRD data (Table 3) and Raman spectrum.
Dolomite CaMg(CO3)2 is one of the major gangue minerals of the Vorontsovskoe deposit. It is abundant in carbonate and carbonatized rocks, wollastonite skarns, beresites, listvenites, and jasperoids. The mineral is studied in details (Sazonov et al., 1991a; Vikentyev et
al., 2016; Soroka et al., 2017, 2018). In our samples, dolomite is present in all mineral assemblages as a main gangue mineral of carbonate breccias. In jasperoids, Sazonov et al. (1991a) described a Fe- and Mn-rich dolomite coexisting with calcite. Assemblage no. 5 contains a Mn-rich dolomite with up to 11.1 wt. % MnO.
Kutnohorite CaMn2+(CO3)2 was identified in one sample collected from the dumps of the southern open pit. It forms crusts and small spherulites of grayish white, locally dark gray color due to the presence of fine-grained manganite (Fig. 33b). The chemical com-
position of the mineral is as follows (wt. %, C02 is calculated by stoichiometry; average of three analyses): 24.24 CaO, 31.53 MnO, 3.29 FeO, 40.54 C02, total 99.60. The empirical formula based on six O atoms is Ca094Mn096Fe010(CO3)2. The strongest reflections of the PXRD pattern [(d, A (/)): 3.72(50), 2.90(100), 2.41(40), 2.20(30), 2.02(30), 1.85(10), 1.80(40), 1.47(10)] and the refined parameters of the hexagonal unit cell correspond to kutnohorite (Table 3).
Malachite Cu2(CO3)(OH)2 is rare in the oxidation zone of the deposit. In samples collected at the dumps of the southern open pit, it forms green fibrous crystals and grains up to 0.5 cm in size, as well as thin films on quartz aggregates (Fig. 33c). It contains only Cu in cationic composition and the parameters of the mono-clinic unit cell correspond to malachite (Table 3).
Rhodochrosite Mn(CO3) was identified in samples from the dumps of the southern open pit. It composes dark gray thin crusts together with kaolinite, cryptomelane, todorokite, and golden yellow pyrite crystals. The mineral contains only Mn in chemical composition; the parameters of the hexagonal unit cell are given in Table 3.
Siderite Fe(CO3) of supergene origin was found in a weathering mantle, where it occurs as small mic-roglobular aggregates up to few tenths of a millimeter in size (Sazonov et al., 1991a). It contains numerous microinclusions of silicates and other minerals. In karst rocks, the fine-grained siderite is common and is associated with goethite, hematite, and, locally, vivianite. Siderite was identified by chemical composition and XRD data.
Sulfates
Anglesite Pb(S04) intergrows with cerussite and forms colorless to pale green (due to the presence of Cu-bearing minerals) thin crusts on quartz with galena, pyrite, and sphalerite in samples with assemblage no. 9 from the dumps of the southern open pit. It contains only Pb and S with a ratio of~l : 1. The parameters of the orthorhombic unit cell are given in Table 3.
Baryte Ba(SO4) is one of the latest minerals of breccias (Vikentyev et al., 2016). Its interstitial aggregates 1-2 mm in size occur between all rock-forming minerals and pyrite. Baryte contains up to 1.5 wt. % SrO. Baryte was found in all mineral assemblages of the carbonate breccias and is one of major gangue minerals in assemblages nos. 1, 3 and 5. Baryte was also found as white radial aggregates up to 1 cm in size
with a strong vitreous luster in fractures of volcanic rocks in samples of assemblage no. 9 from the southern open pit dumps and off-balance ore stockpile no.2. Its chemical composition is close to ideal.
Beaverite-(Cu) Pb(Fe3+2Cu)(SO4)2(OH)6 was found in the oxidation zone of the deposit. In samples with assemblage no. 9 from the dumps of the southern open pit, it forms yellow powdery crusts on oxidized quartz with covellite, djurleite, galena, and malachite (Fig. 33d). The mineral contains (wt. %, H2O calculated by stoichiometry; average of four analyses) 1.41 K20, 13.18 CuO, 27.97 PbO, 23.93 Fe2O3, 3.06 As2O5, 22.45 S03, 8.18 H20, total 100.18. The empirical formula based on 14 O atoms is (Pb083K0 20)1 03(Fe3+198
Cui.i0)3.08(Si.85As0.i8)2.03O8(OH)6- The strongest diffractions of the PXRD pattern and the parameters of the hexagonal unit cell correspond to the alunite structural type (Table 3).
Brochantite Cu4(SO4)(OH)6was found in samples with assemblage no. 9 from the dumps of the southern open pit as light green fine-grained aggregates up to 2 x 1 cm in size on quartz with bornite, calcite, chal-copyrite, galena, malachite, pyrite and tennantite-(Zn) (Fig. 33e). The mineral contains only Cu and S with a ratio of ~4 : 1. The strongest reflections of the PXRD pattern and the parameters of the monoclinic unit cell (Table 3) correspond to brochantite.
Chalcanthite Cu(SO4) • 5H2O is rare in samples with supergene assemblage no. 9 collected from the dumps of the southern open pit, where it forms thin pale blue crusts with a vitreous luster on an aggregate of quartz, calcite, and partly oxidized sulfides (pyrite, chalcopyrite, galena and sphalerite) (Fig. 33f). The mineral contains only Cu and S with a ratio of 1 : 1. The strongest diffractions of the PXRD pattern and the parameters of the triclinic unit cell (Table 3) correspond to the chalcanthite structural type.
Epsomite Mg(SO4) • 7H2O, gypsum Ca(SO4) • 2H2O, pentahydrite Mg(SO4) • 5H2O and starkeyite Mg(SO4) • 4H2O are typical products of post-mining mineral formation found in fragments of the supergene zone collected at the dumps of the southern open pit. Epsomite occurs as white monomineralic crusts on quartz-calcite aggregates. The aggregates of gypsum, pentahydrite, and starkeyite are found in dirty white crusts overgrowing aggregates of quartz, calcite, and fluorapatite with subordinate pyrite, sphalerite, galena, and tetrahedrite-(Zn) (Fig. 33g). Gypsum contains only Ca and S, whereas other sulfates exhibit only Mg and S in chemical composition with a metal/S close to 1:1. Strong reflections of the PXRD pattern of ep-
somite are [d, A (I)]: 5.95(30), 5.32(40), 4.46(20), 4.19(100), 3.42(20), 2.97(20), 2.87(30), 2.65(50). The PXRD data of a gypsum, pentahydrite, and starkeyite mixture are given in Table 8. The unit cell parameters of all sulfates calculated from their PXRD patterns are shown in Table 3.
Wolframates
Scheelite Ca(W04) is a subordinate mineral of
assemblage no. 1. It forms dipyramidal crystals up to 30 x 10 pm in size in calcite and contains small realgar inclusions. Its chemical composition is characterized by significant As content (wt. %, average of two analyses): 73.62 W03, 20.52 CaO, 5.08 As2O5, total 99.22. The empirical formula based on four O atoms is
Cai.02(^0.89AS0.12)S1.01 O4'
Phosphates, arsenates
Minerals of the apatite supergroup include chlorapatite, fluorapatite, hydroxylapatite, svabite, and turneaureite. Abundant fluorapatite Ca5(P04)3F occurs as isometric grains 10-12 pm in size in Mn-bearing calcite of the breccias matrix and contains 6.3-7.2 wt. % As2O5* and 2.4-2.6 wt. % F (Murzin, Varlamov, 2010). Fluorapatite crystals up to 20 pm in size were found among the gangue minerals of metasomatites together with native arsenic and arsenopyrite (Murzin et al., 2011). Fluorapatite contains up to 0.7 wt. % SrO, 0.6 wt. % MnO, 0.2 wt. % As2O5, and 1.6 wt. % CI. Some grains contain significant REE contents: up to 6.4 wt. % Ce2O3,3.2 wt. %La2O3, and 2.0 wt. %Nd2O3.
In our samples, fluorapatite was found in all mineral assemblages except for assemblages no. 2 and 8. In assemblages nos. 1, 4 and 5, it is rare in contrast to other ones. The most interesting zoned fluorapatite from assemblage no. 7 exhibits a broad P-As and F-Cl-OH isomorphic substitutions up to the zones corresponding to hydroxylapatite Ca5(P04)30H, chlorapatite Ca5(P04)3Cl, and turneaureite Ca5(AsO4)3Cl in composition. These members of the apatite group occur in zoned oval grains up to 40 pm in size, which are enclosed in calcite and clinochlore and contain pyrite microinclusions (Fig. 33h). The CI and As content increases from the center of the grain to the edges, thus
* The original values in As2O3 given by authors (Murzin and
Varlamov, 2010; Murzin et al., 2011) were recalculated by us to As2O5
the central part always corresponds to fluorapatite and most edges locally match the composition of turneaureite. Assemblage no. 1 hosts svabite Ca5(AsO4)3F as inclusions upto30 pm in size in baryte with calcite. It contains low amounts of Si and S. The chemical composition of minerals of the apatite supergroup is given in Table 9.
Bayldonite Cu3Pb0(As030H)2(0H)2 is a rare supergene mineral found in samples with assemblage no. 9 from the dumps of the southern open pit. It forms minute green crusts on quartz with azurite, hemimor-phite, and tennantite-(Zn) relics (Fig. 33i). The mineral contains (wt. %, H20 calculated by stoichiometry; average of three analyses): 30.82 CuO, 2.09 ZnO, 31.63 PbO, 30.58 As2O5, 0.37 S03, 4.94 H20, total 100.43. The empirical formula based on eleven O atoms is Pbj 03 (Cu2.83Zno. (As,94S0. 03)i 97°7(OH)4. The strongest reflections of the PXRD pattern [(d, A (I)): 4.90(40), 4.52(40), 3.18(100), 2.93(50), 2.68(50), 2.50(40), 2.27(30)] and the calculated parameters of the mono-clinic unit cell correspond to bayldonite (Table 3).
Chernovite-(Y) Y(AsO4) was found in one sample from assemblage no. 5 as rare dipyramidal crystals up to 30 pm in size in Mn-bearing dolomite. The mineral contains a significant xenotime (0.30 apfu) and low wakefieldite (0.04 apfu) components. Its chemical composition is (wt. %, average of three analyses): 1.23 CaO, 41.06 Y2O3, 0.44 La2O3, 0.74 Ce2O3, 2.25 Nd2O3, 1.01 Sm2O3, 2.36 Gd2O3, 4.09 Dy2O3, 2.09 Er^, 1.93 Yb2O3, 9.36 P2O5, 1.45 V2O5, 32.72 As2O5, total 100.73. The empirical formula based on four O atoms
is (Y0.82Dy0.05Nd0.03Gd0.03El"0.02Yb0.02La0.01Ce0.01Sm0.01 Ca0.05)1.05(As0.64F0.30 V0.04)0.98O4'
Gasparite-(La) La(AsO4) was determined as a
single grain 20 * 10 pm in size in assemblage no. 7 at the contact with alabandite in calcite-dolomite rock. It is associated with tsygankoite and arsenopyrite. Gas-parite-(La) contains (wt. %, average of three analyses): 2.23 CaO, 36.73 La2O3, 14.70 Ce2O3, 1.37 Pr2O3, 2.39 Nd2O3, 41.98 As2O5, total 99.40. Its empirical formula based on four O atoms is (Lan „Cen ,,5Ndn n.Prn m
v 0.62 0.25 0.04 0.02
Ca0.11)1.04Asi.00O4'
Tilasite CaMg(AsO4)F was found in assemblage no. 7, where it forms anhedral grains up to 0.2 mm in size intergrown with duranusite, tsygankoite, orpiment, and realgar in dolomite and calcite (Figs. 8d, 26g). The mineral contains (wt. %, average of five analyses) 50.85 As2O5, 24.97 Ca0,18.02 MgO, 9.21 F, —3.88 O = F, total 99.17. Its empirical formula based on O + F = 5 anions is Ca099Mg100(As099O392)491F108. The strongest reflections of the PXRD pattern and the
Table 8
Powder XRD data of sample 1091P with pentahydrite, starkeyite and gypsum
d, Â (I, %) sample 1091P Pentahydrite [JCPDS-ICDD, 250532] Starkeyite [JCPDS-ICDD, 24-0720] Gypsum [JCPDS-ICDD, 330311]
10.358(5) 10.31(5)
7.682(10) 7.63(100)
6.896(25) 6.83(45)
5.853(15) 5.84(20)
5.648(10) 5.62(10)
5.470(60) 5.43(75)
5.160(15) 5.15(30) 5.15(8)
4.966(30) 4.93(100)
4.828(5) 4.83(5)
4.735(30) 4.70(35)
4.491(100) 4.46(100)
4.351(10) 4.34(5)
4.283(5) 4.283(100)
3.974(60) 3.951(65)
3.817(10) 3.794(8) 3.799(17)
3.667(20) 3.65(30)
3.616(10) 3.598(12)
3.475(10) 3.46(15)
3.415(50) 3.398(45)
3.272(15) 3.26(40) 3.263(6)
3.231(40) 3.216(40)
3.165(5) 3.15(10)
3.078(5) 3.065(75)
3.043(15) 3.03(20)
3.019(5) 3.007(5) 3.00(20)
2.989(20) 2.99(5) 2.978(20)
2.958(70) 2.95(30) 2.946(55)
2.907(5) 2.90(5) 2.892(8) 2.873(45)
2.800(10) 2.79(25)
2.779(25) 2.769(25) 2.789(10)
2.765(20) 2.755(14)
2.707(10) 2.69(15) 2.702(6)
2.685(20) 2.68(25) 2.685(35)
2.564(25) 2.546(10) 2.537(20) 2.555(20)
2.485(10) 2.489(5) 2.478(8) 2.495(11)
2.465(20) 2.466(5) 2.458(14)
2.430(25) 2.422(20)
2.406(5) 2.407(15)
2.361(15) 2.360(5) 2.351(14)
2.285(15) 2.280(5) 2.279(10)
2.273(20) 2.266(25)
2.228(5) 2.219(15)
2.186(5) 2.182(5)
1.998(5) 1.995(35) 1.965(8)
1.882(10) 1.880(5) 1.877(8)
1.799(10) 1.795(10)
1.721(5) 1.729(10) 1.718(6)
Note. Only reflections with/el > 5% are included.
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parameters of the monoclinic unit cell correspond to tilasite (Table 3).
Vivianite Fe2+3(P04)2 * 8H2O was found in Fe-rich ocher montmorillonite areas of karst rocks (Sazonov et al., 1991a). It forms gray blue to indigo blue fractured lenses up to 3 mm long and up to 1 mm thick. The identification of vivianite is supported by chemical composition and PXRD data.
Silicates
Amphiboles were found in propylitized rocks of the deposit (Sazonov et al., 1991a). They include hornblende and an amphibole of the actinolite-trem-olite series. According to the current nomenclature, the composition of this «hornblende» (Sazonov et al., 1991a) corresponds to magnesio-ferri-hornblende □ Ca2(Mg4Fe3+)(AlSi7O22)(OH)2. Colorless acicular tremolite crystals □Ca2(Mg50 45Fe2+00 05)Si8O22(OH)2 were found in skarns and wollastonite skarns. The mineral was determined by optical properties. Tremolite was also described as a rare mineral in the matrix of the carbonate breccias (Murzin, Varlamov, 2010).
In our samples, tremolite occurs as creamy white radial aggregates of fine-fibrous crystals up to 0.5 cm long in assemblage with brownish massive talc enclosed in white marble (Fig. 34a). The chemical composition of the mineral is given in Table 10. The calculated parameters of the monoclinic unit cell are given in Table 3.
Pargasite NaCa2(Mg4Al)(Si6Al2)O22(OH)2 was found in samples from the dumps of the northern open pit. The mineral forms black prismatic crystals with a vitreous luster uptolx0.5cmin size in lamprophyre (Fig. 34b). Its chemical composition and calculated parameters of the monoclinic unit cell are given in Tables 10 and 3, respectively.
Armenite BaCa2(Al6Si9)O30 • 2H2O was identified in samples with assemblage no. 1 from the main ore stockpile specimens (Kasatkin, 2019). It forms white aggregates up to 1 mm in size with a vitreous luster and intergrows with calcite, clinochlore, dolomite, muscovite, and pyrite in metasomatite (Fig. 34c). Other associated ore minerals include boscardinite, chabourné-ite, christite, cinnabar, coloradoite, dalnegroite, native gold, metacinnabar, parapierrotite, and routhierite. The reflectance values of armenite are much higher than of the associated gangue minerals. In reflected light, it looks light gray at the contact with dark gray clino-chlore, muscovite, and calcite. In immersion, the reflectance values of armenite strongly decrease: it looks dark gray in comparison with almost black associated
Fig. 34. Silicates of the Vorontsovskoe deposit:
a - veinlet of creamy white radial aggregates of fibrous tremolite in white marble; b - black prismatic pargasite crystals in lamprophyre; c - abundant aggregates of armenite (moderate gray) intergrown with muscovite and clinochlore (dark gray zones) and pyrite (numerous light gray rounded grains); d - greenish yellow powdery aggregates of chapmanite on calcite with quartz and stibnite; e - crust of andradite crystals on calcite; f - radial aggregates of colorless prismatic hemimorphite crystals on quartz in assemblage with dark brown earthy crusts of cesarolite; g - dark brown massive chrysotile-2Orc1 on calcite; h - yellow aggregates of chrysotile-2Orc1 on dolomite with pyrite and magnetite; i - light green massive pigeonite intergrown with chrysotile-20^ in dark matrix; j - violet aggregates of Ba,Mg,Mn-bearing muscovite in dolomite-calcite marble with pyrite and orange realgar; k - greenish blue crust of celadonite-ferroceladonite on carbonate matrix; 1 - thorite aggregate with cinnabar inclusions in microcline.
Collections: A.V Kasatkin (a-c, f-h,j-l), Museum «Shtufnoi Kabinet», Severouralsk (d, e, i). Photo: A.D. Kasatkina (a, b, f-h,j, k), M.V. Tsyganko (d, e, i); BSE images (c, 1).
gangue minerals. Bireflectance and anisotropy are distinct in gray tones and are much more intense in immersion. The chemical composition of armenite and the parameters of its orthorhombic unit cell are given in Tables 10 and 3, respectively. This is the first finding of the mineral in the Russian Federation.
Chapmanite Fe3+2Sb3+(SiO4)2(OH) was established in samples from the main ore stockpile of the deposit (Kasatkin, 2019). The mineral forms thin greenish yellow crusts and powdery coatings on brec-ciated rock, which is composed of calcite, quartz, and stibnite (Fig. 34d). Chapmanite contains (wt. %, H2O calculated by stoichiometry; average of five analyses): 32.90 Fe2O3; 35.06 Sb2O3; 27.45 Si02, 2.04 A12O3; 2.06 H20, total 99.51. Its empirical formula based on nine O atoms is (Fe3+179Al017)196Sb3+105Si199O8(OH). The strongest reflections of the PXRD pattern are [d,
A (/)]: 7.614(100), 4.168(20), 3.874(40), 3.573(60), 3.182(40), 2.908(20), 2.587(30). The calculated parameters of the monoclinic unit cell are consistent with those of chapmanite (Table 3). This is the first finding of this mineral in the Russian Federation.
Chlorites are the most abundant minerals in altered rocks of the deposit. They are widely distributed in skarns, propylites, beresites, and listvenites. Chlorites include a common clinochlore Mg5Al(AlSi3O10) (OH)8 and a rarer chamosite (Fe2+,Mg,Al,Fe3+)6(Si,A1)4 O10(OH,O)8. They compose colorless (in limestones) to grayish green and green (in metasomatites) flakes few tens of micrometers and smaller. Chlorites were determined by chemical composition, PXRD patterns and optical parameters (Sazonov et al., 1991a). The rock-forming clinochlore was found in assemblages nos. 1, 2 and 7. The colorless clinochlore from assemblage no.
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Chemical composition (wt. %) of silicates
Table 10
An. no. Mineral Na20 K2o CaO BaO MgO MnO FeO ai2o, Fe20, Ti02 Si02 H20* Total Fonnula
1 Andradite - - 35.2 - - - - 8.11 18.94 1.49 37.94 101.68 Ca2.99Fe^13AWTi0.(Ä.0<A2
2 Annenite - - 9.85 13.09 - - - 26.72 - - 47.08 3.14 99.88 Ba„98Ca2 02Al601Si899O3„-2H2O
3 Augite - - 15.14 - 19.41 1.80 0.96 7.67 - - 55.07 100.05 (Mgl.01Ca0,7A10.32Mn0.05Fe2+0.03)l.98Si1.93O6
4 Celadonite - 11.01 - - 5.34 - 8.12 4.98 10.78 - 56.79 4.26 101.28 K„,9Mg0,6Fe-048Fe-057Al041Si400O10(OH)2
5 Chabazite-Ca - 1.75 7.56 2.57 - - - 18.56 - - 47.16 22.32 99.92 (Ca,,2K039Ba018)199A1,82Si824024 • 13H20
6 Chamosite - - - - 9.14 - 34.43 16.16 - - 27.86 10.86 98.45 Fe2+3,8Mg151Al210Si3 08O10(OH)8
7 Clirysotile-20r j - - - - 40.65 - 3.81 - - - 43.24 12.88 100.58 (Mg2,2Fe-0 15)297Si401O5(OH)4
8 Clinochlore - - - - 39.15 - - 13.47 - - 33.86 12.84 99.32 Mg5 45Al148Si316O10(OH)8
9 Diopside - - 25.99 - 17.19 - 1.64 - - - 54.44 99.22 Cai.02Mg0.94Fe2+0.05Si2.00O6
10 Ferroceladonite - 10.45 - - 4.08 - 9.46 5.16 11.17 - 56.69 4.24 101.25 K„,4Fe-,56Mg043Fe-59Al043Si400O10(OH)2
11 Grossular - - 36.56 - - - - 14.40 11.17 0.83 39.45 102.41 Ca2 99 Alj 29Fe^+0 64Ti0 05Si3 01O12
12 Hannotome - 1.28 0.36 21.82 - - - 15.62 - - 45.68 14.48 99.24 (Ba213K041Ca0 10)264(Al458Siu 36)032 • 12H20
13 Johannsenite - - 23.38 - 1.79 25.25 0.88 0.55 - - 47.58 99.43 Cai.03Mn0.88Mg0.11Fe2+0.03A10.03Si1.96°6
14 Laumontite - 0.87 11.78 - - - - 22.02 - - 51.44 15.50 101.61 (Ca0,8K0,9)L07Al201Si3 98O12-4H2O
15 Muscovite-2Mj 9.39 1.74 0.95 5.99 0.92 28.96 1.79 45.73 4.45 99.92 (K0.8iCa013Ba0 03)097(Al230Mg060Ti009Mn0 05)3 04
Si3 08Oio(OH)2
16 Pargasite 2.43 0.90 12.71 - 14.20 - 8.32 15.64 - 0.66 42.55 2.07 99.48 (Nao.66Ko.i7)(Nao.o2Ca1.98)2.„„(Mg3.07Fe2+101 Al0 86 Ti007)5 01(Si618A118A,)(OH)2
17 Pigeonite - - 5.50 - 34.08 - 1.71 3.15 - - 55.17 99.61 (Mg1.75Ca020Fe-005)200(Si190Al0 13)2 03O6
18 Prehnite - - 27.02 - - - - 24.17 - - 44.55 4.38 100.12 Ca198A1i95Si3„5O10(OH)2
19 Pumpellyite-Mg - - 23.49 - 4.47 0.38 0.08 23.70 - - 37.81 6.81 100.00 Ca2.00(A12.22Mg0.53V3+0.21Mn0.02Fe2+0.0l)2.99Si3.00°il.40 (OH)160H2O
20 Talc - - - - 28.02 1.10 4.21 - - - 62.23 4.65 100.21 (Mg2,9Mno,3Fe„,6)2,8Si4,1010(OH)2
21 Tremolite 0.16 0.25 13.23 21.69 0.27 3.35 1.29 57.10 2.17 99.51 K0,4(Na0.04Cai.96)2.00(Mg4.47Fe2+0.39A10.11Mn0,3)5,0
(s^oMnoCym
22 Vesuvianite - - 36.37 - 0.25 3.04 1.51 19.76 - - 36.52 2.55 100.00 Cai9(Al11.36Mn1.26Fe0.62Mg0.18)13.42Si69.56O74(OH)8.29
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Note. The H20 content is calculated by stoichiometry in all analyses except analyses nos. 19 and 22, where it is calculated by total deficiency. The Fe2+/Fe3+ ratio in analyses nos. 4 and 10 is calculated from the charge balance. The analysis no. 19 contains 3.26 wt. % V203.
Samples: 1044A- an. 1; 928A - an. 2; Vor-8bis-l - an. 3; 1002C - an. 4, 10; 312Sh- an. 5; Vor-08/18-15 - an. 6; 547Ch- an. 7; Vor-10/2017-1 - an. 8; Vor-CC-lb - an. 9; Vor-05/18-9 - an. 11; Vor-2013new-l - an. 12; Vor-08/20-9 - an. 13; 535L - an. 14; 1374M - an. 15; 920P - an. 16; 1073P - an. 17; Vor-01/19-22 - an. 18; Vor-2013-8-1 - an. 19; 661T - an. 20; 795T - an. 21; Vor-08/18-13 - an. 14.
The mineral formulas are recalculated to four Si and 12 O atoms (celadonite, ferroceladonite), six (augite, diopside, johannsenite, pigeonite), nine (chrysotile-2Orcl), 12 (andradite, grossular, muscovite-2A/1, prehnite, talc), 18 (chamosite, clinochlore) and 24 (pargasite, tremolite), 12 O atoms and 4 H20 molecules (laumontite), 13 O and one H20 molecule (pumpellyite-Mg), 24 O atoms and 13 H20 molecules (chabazite-Ca), 30 O atoms and 2 H20 molecules (annenite), 32 O atoms and 12 H20 molecules (hannotome) and 19 Ca atoms (vesuvianite).
4 contains no Fe in its composition (Table 10). Cha-mosite was identified only in sample Vor-08/18-15 (Table 10). The parameters of the triclinic unit cells of chlorites calculated from their PXRD patterns are given in Table 3.
Epidote Ca2(Al2Fe3+)[Si2O7][SiO4]0(0H) is abundant in various metasomatites of the deposit. Sazonov et al. (1991a) describe three morphological varieties of the mineral: isometric grains up to 2 mm thick, veinlets up to 3 mm thick, and powder aggregates. The mineral was identified by its chemical composition. In cal-cite-garnet-epidote skarns with late magnetite-sulfide mineralization (the dumps of the southern open pit), epidote was found in assemblage no. 8 with rare Bi and Te minerals.
Feldspars include albite, microcline, and ortho-clase. Albite Na(AlSi3O8) (including oligoclase) is rare in metasomatites and forms aggregates of pm-sized grains with microinclusions of other minerals. Microcline K(AlSi3O8) occurs in zones of K-feldspar alteration of rocks of the intrusive diorite-granodi-orite complex and associated andesites. Orthoclase K(AlSi3O8) was found in metasomatites with gold mineralization in form of fine (few tens of micrometers) grains with microinclusions of chlorites and other minerals. All feldspars were identified by chemical composition and PXRD patterns (Sazonov et al., 1991a). Kabanov (2001) mentioned feldspars in the oxidation zone. Later, microcline and orthoclase from igneous rocks of diorite-granodiorite composition and volca-nosedimentary rocks (tuffites, tuffaceous siltstones and tuffaceous sandstones) were studied by XRD and thermal analyses (Rovnushkin et al., 2010). Feldspars are extremely rare in carbonate breccias. Only rare grains of albite and Ba-bearing orthoclase (hyalophane, up to 9.6 wt. % BaO) were found in gangue minerals of breccias (assemblage no. 1).
Garnets of the Vorontsovskoe deposit include andradite and grossular. Andradite Ca3Fe3+2(SiO4)3 was found in samples from the dumps of the southern open pit. It is present in calcite-garnet-epidote skarns with late magnetite-sulfide mineralization. Striking druses of dark red opaque andradite tetragontrioctahe-dra up to 1 cm in size were etched from calcite (Fig. 34e). The associated minerals include chalcopyrite, epidote, magnetite, pyrite, and sphalerite. Andradite contains a significant grossular component in chemical composition (Table 10). Grossular Ca3Al2(SiO4)3 was described in fine-grained mica-calcite-chlorite and medium-grained pyrite-calcite-grossular metasomatites (Sazonov et al., 1991a). It occurs as finest dis-
semination and, less often, veinlets up to several millimeters thick. The color of grossular is light yellow, locally, white, olive-green or green. It was determined by chemical composition and PXRD data. In calcite-garnet-epidote skarns with andradite, grossular forms significantly rare smaller (<0.5 mm) transparent greenish yellow crystals. The chemical composition is given in Table 10.
Hemimorphite Zn4(Si2O7)(OH)2 • H2O is a rare mineral of the oxidation zone identified in samples from the dumps of the southern open pit. It forms radial aggregates of the colorless prismatic crystals up to 0.7 cm long on quartz in assemblage with cesarolite, galena, chalcopyrite, and malachite (Figs. 31e, 34f). Hemimorphite also occurs as small white and pale blue (probably, due to a low Cu content) spherules on quartz with bayldonite, malachite, pyrite, and tennantite-(Zn) (Fig. 33i). The mineral contains only Zn and Si at a 2:1 ratio. The parameters of the orthorhombic unit cell are given in Table 3.
Hingganite-(Y) Y2DBe2Si2O8(OH)2 and hingganite-(Nd) Nd2DBe2Si2O8(OH)2 were identified in a sample collected from the main ore stockpile of the deposit. Both minerals compose the grains up to 10 pm in size in dolomite-calcite rock and are associated with baryte, fergusonite-(Y), Cr-bearing magnetite, pyrite, realgar, routhierite, and wakabayashilite. These grains are chemically heterogeneous with areas dominated by Y or Nd among REEs. Hingganite-(Y)/hingganite-(Nd) contain (wt.%, BeO and H2O calculated by stoichi-ometry): 10.10/10.43 BeO, 1.21/1.78 CaO, 4.19/2.60 FeO, 12.71/11.03 Y2O3, 1.05/0.99 La2O3, 8.45/7.36 Ce2O3, 2.34/2.15 Pr203, 14.17/17.89 Nd2O3, 5.84/5.86 Sm2O3, 1.05/1.14 Eu2O3, 5.92/6.12 Gd2O3, 0.52/0.48 Tb2O3, 2.98/2.87 Dy2O3, 0.44/0.34 Ho^, 1.19/1.09 Er2O3, 0.75/0.88 Tm2O3, 0.58/0.52 Yb2O3, 24.46/24.66 SiO2, 3.24/3.25 H20, total 101.19/101.4^3. The empirical formulas on the basis of two Si atoms and O + OH = 10 apfu are: (Y055Nd041Ce025Sm016Gd016Dy0 08Pr007 La,003Eu003Er003Tm002Tb001Ho001Yb001Ca011)193(D071
Fe2+0.29)1.00Be2.00Si2.00O8.24(OH)l.76 and (Nd0.52Y0.48Ce0.22 Sm0.16Gd0.16Dy0.08 Pr0.06La0.03Eu0.03Er0.03Tm0.02Tb0.01
Hn Yb Ca ) (n Fe2+ ) Be Si O
"0.01 u0.0^a0.1V1.9^^0.8^ 0.18-M.00 2.00 2.00 8.24
(OH)j 76, respectively. In spite of the absence of XRD data because of the small grain size of minerals, the above compositions, in our opinion, belong to the minerals of the hingganite series. The deficit in totals is correlated with the calculated BeO and H20 contents. The Fe content of both minerals is typical of hinggan-ite; other silicates with an atomic REE/Si ratio close to 1 : 1 contain no Fe. Similar chemical zonation with
dominant Y or Nd in various zones was described in hingganite-(Nd) from its type locality, Mt. Zagi in Pakistan (Kasatkin et al., 2020d). The finding of hinggan-ite-(Nd) is the first in the Russian Federation.
The kaolinite-serpentine group at the deposit includes four minerals.Three polymorphs of the kao-linite subgroup (dickite, halloysite, kaolinite Al2(Si2O5) (OH)4) and a member of the serpentine subgroup (chrysotile-2Orc1) were identified in samples with assemblage no. 9 collected at the dumps of the southern open pit.
Dickite is a subordinate mineral in yellow-white powdery aggregates with major kaolinite. It was determined by chemical composition (Al/Si ratio of ~1 : 1) and IR spectrum (the main bands at 430,470, 537, 695, 797, 912, 1007, 1031, 1625, 3650 cm1). Dickite differs from kaolinite by a characteristic band at 3650 cm-1 in a region of O-H stretching vibrations.
Halloysite was mentioned in the oxidation zone of the deposit (Kabanov, 2001). In our samples, this mineral was found in brown and black powdery polymineral crust with kaolinite, calcite, quartz, and rhodochrosite (Fig. 32i). The mineral was identified by qualitative chemical composition (Al/Si ratio of ~1 : 1), PXRD pattern (the strongest reflections at [d, A (/)]: 7.27(100), 4.44(80), 3.65(50), 2.57(20), 1.70(10), 1.48(10)), and IR spectrum. The parameters of the monoclinic unit cell correspond to halloysite-7A (Table 3).
Kaolinite is abundant in the deposit and is a subordinate mineral in the supergene zone. It was determined by XRD in polymineral samples of various rocks of the deposit (Sazonov et al., 1991a). In our samples from the oxidation zone from dumps of the southern open pit, kaolinite is one of the major rock-forming minerals. In some samples, it composes up to 80 vol. % hosting the fine-grained quartz. Due to the presence of Fe and Mn oxides, kaolinite is often characterized by abrown color (Figs. 31d, 32i). It contains only Al and Si at an approximate ratio of 1 : 1. The strong reflections of the PXRD pattern [(d, A (/)): 7.12(100), 4.39(40), 4.17(30), 3.54(50), 2.55(30), 1.97(10), 1.66(10), 1.49(20)], the parameters of the triclinic unit cell (Table 3), and the main bands in IR spectrum (at 432, 469, 536, 691, 796, 912, 1008, 1031, 1627, 3620, 3697 cm-1) correspond to kaolinite. A characteristic feature of the mineral is a doublet in the IR spectrum in a region of OH-groups that consists of two narrow bands at 3620 and 3697 cm-1, which is absent in the IR spectrum of dickite and halloysite.
Chrysotile-20rcl Mg3Si2O5(OH)4 forms dark brown and yellow aggregates on calcite and dolomite with pyrite and magnetite (Figs. 34g, 34h) and light green massive aggregates with pigeonite in a dark gray rock mainly consisting of clinochlore, Fe-bearing gros-sular, fluorapatite, titanite, baryte, pyrite, and chalco-pyrite (Fig. 34i). Chrysotile contains a low Fe content (Table 10). The parameters of the orthorhombic unit cell correspond to the 2Orc1 polytype (Table 3). The characteristic bands in the iR spectrum are at 384, 404, 438, 564, 613, 960, 1025, 1074, 3687 cm-1.
The minerals of the mica group at the deposit, first of all, include muscovite KAl2(Si3Al)O10(OH)2, which is abundant in quartz-sericite metasomatites and, to a lesser extent, in beresites and listvenites. In addition, muscovite occurs in propylites after intermediate-mafic volcanic rocks and rocks of the intrusive diorite-granodiorite complex. Muscovite composes flakes up to 1 mm in size that are dispersed among the grains of other minerals. It is identified by chemical composition and PXRD pattern (Sazonov etal., 1991a).
In our samples, muscovite was found in four mineral assemblages. In assemblage no. 1, it is a rock-forming mineral, which is associated with clino-chlore and armenite. An atypical purple aggregates of Ba,Ca,Mg,Mn,Ti-bearing muscovite were found in a dolomite-calcite marble with pyrite and realgar (Fig. 34j; Table 10). The parameters of its monoclinic unit cell correspond to the 2M1 polytype (Table 3).
Celadonite KMgFe3+Si4O10(OH)2 and ferroce-ladonite KFe2+Fe3+Si4O10(OH)2 were found in samples collected at the dumps of the northern open pit. Together with calcite, the micas form pale greenish blue crusts that are overgrown by late colorless cal-cite crystals (Fig. 34k). Celadonite and ferroceladonite are macroscopically indistinguishable and even grains of few tens of micrometer in size could be composed of both minerals. The chemical compositions of the minerals are given in Table 10. The parameters of the monoclinic unit cell correspond to a Si-rich dioctahe-dral mica (Table 3).
Prehnite Ca2Al(Si3Al)O10(OH)2 occurs in propy-litizes rocks (Sazonov et al., 1991a). In assemblage no. 1, prehnite is a rock-forming mineral of propylites superimposed on carbonate breccias. It was also found in gangue minerals ofbreccias in assemblages nos. 4 and 5. Its chemical composition is close to ideal (Table 10).
Pumpellyite was described in propylites (Sazonov et al., 1991a; Vikentyev et al., 2016). We identified pumpellyite-(Mg) Ca2MgAl2(Si2O7)(SiO4)(OH)2 • H2O that forms 50-70 pm aggregates in assemblage
no. 1 of metasomatic rocks superimposed on carbonate breccias. The mineral is associated with armenite, baryte, calcite, fluorapatite, muscovite, chabourneite, christite, cinnabar, native gold, pyrite, routhierite, and sphalerite. Pumpellyite-(Mg) contains small amount of V, which is an atypical chemical element for the Vo-rontsovskoe deposit(Table 10).
Pyroxenes are the subordinate to rare minerals of the deposit. Augite (Ca,Mg,Fe)2Si2O6 rarely occurs in meta-somatites, which are superimposed on carbonate breccias with minerals of assemblage no. 1. Diopside CaMgSi2O6 is abundant amid gangue minerals of assemblage no. 5 and is rarer in assemblages nos. 1, 4 and 6. In a sample from off-balance ore stockpile no. 2, we detected a diopside rich in Mn up to the compositions corresponding to jo-hannsenite CaMnSi2O6. Pigeonite (Mg,Fe,Ca)2Si2O6 was found in samples from the dumps of the southern open pit, where it intergrows with chrysotile-2Orc1 in large (up to 5 x 3 cm) massive yellow-green grains in light calcite-do-lomite marble (Fig. 34i). The chemical composition and the parameters of the monoclinic unit cell of pigeonite are given in Tables 10 and 3, respectively. The chemical composition of other pyroxenes is also shown in Table 10.
Subordinate smectites are typical of the oxidation zone of the deposit. Beidellite (Na,Ca)03A l2(Si,Al)4O10(OH)2 • nH2O, montmorillonite (Na, Ca)a3(Al,Mg)2Si4O10(OH)2 • nH2O, and nontronite Na03Fe3+2(Si,Al)4O10(OH)2 • nH20 were identified by chemical composition and PXRD patterns in several samples (Sazonov et al., 1991a). Nontronite-15A was identified in a sample from the dumps of the northern open pit as a yellow powdery films on fine-grained calcite. Its identification is confirmed by qualitative chemical analysis (major Fe, Si and O and minor Na and Ca) and PXRD pattern (strong reflections at [d, A (I)]: 15.20(100), 4.50(20), 3.04(50), 2.58(10), 2.28(20), 1.71(5), 1.52(20) h 1.34(5) A)) and IR spectrum (main bands at 428, 490, 682, 818, 1017, 1100 (a shoulder), 1636, 3419, 3560 cm1).
Talc Mg3Si4O10(OH)2 composes leaf aggregates in carbonates of the breccia matrix (Murzin, Varlamov, 2010). Talc in samples from the main ore stockpile forms bluish green massive aggregates in dolomite in assemblage with arsenopyrite crystals. In some samples, talc forms white and brownish films on calcite and intergrows with clinochlore and muscovite. Talc is identified as a rare mineral of metasomatites in assemblage no. 3. The mineral contains up to 1.1 wt. % MnO (Table 10). The parameters of the triclinic unit cell correspond to talc (Table 3).
Thorite Th(SiO4) (or, possibly, its dimorph hut-
tonite) was found in assemblage no. 1 as a grain 0.1 x 0.03 mm in size in Ba-containing orthoclase with diopside. Thorite hosts a small cinnabar inclusions (Fig. 341). It contains only Th and Si at a ratio close to 1:1. The mineral is X-ray amorphous as a result of metamictic decay.
Titanite CaTi(SiO4)O forms rare crystals up to 20 pm in size in siliceous breccia fragments. It contains up to 1.3 wt. % A12O3 and 0.9 wt. % V2O5 (Murzin, Varlamov, 2010). Titanite was also found as a rare accessory of assemblages nos. 1 and 6. It is more common for the gangue minerals of breccias (assemblage no. 7).
Vesuvianite (Ca,Na)19(Al,Mg,Fe)13(SiO4)10(Si2 O7)4(0H,F,0)10 is a rare mineral of metasomatites and was found in assemblage no. 6 in aggregates with diopside and fluorapatite. It contains numerous inclusions of arsenopyrite, benavidesite, galena, native arsenic, orpiment, pyrite, ramdohrite, realgar, tetrahedrite-(Fe), and tetrahedrite-(Zn). The chemical composition of vesuvianite is given in Table 10.
Wollastonite CaSiO3 occurs in skarns and wol-lastonite skarns confined to faults (Sazonov et al., 1991a). In skarns, it composes almost monomineralic rims between the zones of garnet skarns and marblized limestones. The wollastonite crystals form colorless sheaf-like aggregates. The mineral was identified by its chemical composition, XRD, and optical data.
The minerals of the zeolite group include chabazite-Ca, harmotome, and laumontite. Chabazite was described as an abundant mineral that forms veins in pro-pylitized andesites, basaltic andesites, mafic dikes, rocks of the intrusive diorite-granodiorite complex, skarns, and epidosites (Sazonov et al., 1991a). Chabazite-Ca Ca2[Al4Si8O24] • 13H2O was found in a sample from the dumps of the southern open pit (Table 10). It forms pinkish fine-grained crusts on marblized limestone and is associated with small (up to 0.3 mm) pyrite crystals. The parameters of the triclinic unit cell correspond to the mineral of the chabazite series (Table 3).
Harmotome Ba2(Si12Al4)O32 • 12H2O was identified in assemblage no. 1 as anhedral grains up to 0.2 * 0.1 mm in size in calcite with pyrite, realgar, orpiment, Ag-bearing native gold, chabourneite, parapierrotite, routhierite, and weissbergite. The identification of the mineral was confirmed by EMPA (Table 10).
Laumontite CaAl2Si4O12 • 4H2O was first found in a stringer-disseminated zone with gold mineralization in assemblage with grossular, K-feldspar, and quartz (Sazonov et al., 1991a). In samples from the dumps
of the northern open pit, laumontite forms creamy pockets up to 5 x 5 mm in size in white calcite with pyrite crystals. In contrast to laumontite described by (Sazonov et al., 1991a), the mineral from the northern open pit contains only low amount of K (Table 10). The parameters of the monoclinic unit cell correspond to laumontite (Table 3).
Zircon Zr(Si04) is a rare accessory mineral of assemblage no. 1 from metasomatites superimposed on carbonate breccias. Its chemical composition is close to ideal.
Specific features of mineralogy of the Vorontsovskoe gold deposit
Most researchers agree that the Vorontsovskoe deposit has several stages of mineral formation. The early ore types (skarns and disseminated ores) of the deposit are hosts to the arsenopyrite-pyrite-chalcopyrite-sphalerite-galena assemblage and the tuffaceous rocks are characterized by pyrite-arsenopyrite-fahlore assemblage with native arsenic and realgar, the presence of which indicates an increasing S fugacity (Sazonov et al., 1991a, Stepanov et al., 2017, 2021; Murzin et al., 2017, Vikentyev et al., 2019). The carbonate breccias with carbonate-tuffaceous matrix contain goldpyrite-realgar ores with remarkably diverse sulfosalts. Evaluation of the formation conditions of the sulfosalt assemblages is complicated by fine grain size of ore minerals and their close assemblage with other minerals formed at different hydrothermal stages.
On the one hand, a number of sulfosalts including new minerals are characterized by unique chemical composition and structure. On the other hand, many of them belong to an homologous series that are typical of geochemical conditions similar to that observed at the Vorontsovskoe deposit. Eleven Pb-Tl-Sb-As sulfosalts (boscardinite, chabourneite, dufrenoysite, ecrinsite, enneasartorite, guettardite, heptasartorite, parapierrotite, philrothite, twinnite, veenite) belong to the sartorite homologous series. Minerals of this series consist in principle of diagonal slabs formed by As(Sb)-S double-ribbons, which are separated by zigzag walls of large coordination polyhedra of Pb and Tl, and joined into a herringbone-like structure (Berlepsch et al., 2001; Makovicky, Topa, 2015).
Five Pb-Tl-Sb-As sulfosalts (lillianite, andorite-VI, ramdohrite, roshchinite, vikingite) are the members of the lillianite homologous series. Lillianite occurs in magnetite-garnet-epidote skarns, whereas other members of its group are hosted in carbonate breccias.
Most of them are combinations of Pb-Ag-Sb(As)-S in the andorite subseries, whereas the members of the Pb-Ag-Bi-S, lillianite-gustavite subseries are rare at the Vorontsovskoe deposit. In this series, the diagonal slabs with galena-like arrangement are mirror-twinned to form the structure, which, thanks to its properties, shows preference for Sb and/or Bi over As (Makovicky, Topa, 2014).
The pavonite homologous series includes rare pa-vonite and luborzakite, a new Bi-free As-Sb-Mn mineral. These two minerals are also observed in different assemblages: pavonite (as well as the most Bi minerals of the deposit) occurs in magnetite-garnet-epidote skarns, whereas luborzakite is confined to carbonate breccias. In the luborzakite structure, the right mixture of lone-electron pair active and inactive elements allows the pavonite-like motif to form (Kasatkin et al., 2020a).
The plagionite homologous series includes three Pb-Sb members: heteromorphite, plagionite, and sem-seyite. The jordanite homologous series is characterized by the presence of jordanite and geocronite, another important Pb-Sb structure present is meneghi-nite, and the Tl-As homologous pair bernardite-hutch-insonite. To the latter, we can add the modified quasi-member, imhofite, too. The polybasite series consists of polybasite, cupropolybasite, and benleonardite. The tetrahedrite-vorontsovite «over-group», which combines minerals with perfect-to-defect tetrahedrite-like structures, includes, on the one hand, argentotetrahe-drite-(Fe), argentotetrahedrite-(Zn), tennantite-(Fe), tennantite-(Zn), tetrahedrite-(Fe), and tetrahedrite-(Zn), and, on the other hand, minerals with Tl in the structure cages (galkhaite, vorontsovite, ferrovoront-sovite, routhierite, arsiccioite, stalderite). Aktashite, nowackiite, sinnerite, and laffittite are related to these minerals in chemical composition and structures.
The presence of sulfosalts of various homologous series and structural types means that these minerals are successfully adjusted to the variable chemical and physical conditions of mineral formation via, e.g., cation substitution (Sb,Bi) + Ag ^ 2 Pb and/or As(Sb)+Tl ^ 2 Pb with preservation of their structure schemes (Moelo et al., 2008). The examples of broad cation substitution include andorite, philrothite, ecrinsite, boscardinite, ramdohrite, etc.
The Vorontsovskoe deposit is As-rich, whereas the high Sb contents are locally detected and Bi contents are low. The deposit is also Mn-rich in contrast to similar Lengenbach (Switzerland) and Allchar (North Macedonia) deposits. Rock-forming Mn-bearing dolomite and calcite are most likely the source of Mn for
numerous ore minerals: sulfides (alabandite) and sul-fosalts (auerbakhite, benavidesite, clerite, luborzákite, tsygankoite, etc.). Manganese is also present as a species-defining element in oxides, hydroxides, carbonates and silicates.
Twenty three Ag minerals have been identified at the Vorontsovskoe deposit, but most Ag minerals occur as single grains, e.g., acanthite, arsiccioite, jal-paite, laffittite, manganoquadratite, oyonite, pavonite, ramdohrite, sicherite, and tsnigriite. Only two sulfo-salts (boscardinite, écrinsite) are relatively abundant, however, they contain minor Ag amount. Bismuth is mainly present in assemblage no. 8, which is confined to skarns. Eight Bi minerals are identified at the deposit and only vikingite and bismoclite were found in breccias. Tellurium is a trace element of the deposit, which is hosted in five minerals. Coloradoite is relatively common in comparison with other Te minerals that are confined only to skarns. No Se minerals have been found at the deposit. Selenium is detected in a minor amounts only in cinnabar.
Telescoping of various geological processes and the formation of metasomatites after various rocks were responsible for the crystallization of specific ore and gangue minerals in ores of the Vorontsovskoe deposit. The formation of various assemblages of oxygen-bearing minerals is a result of a successive evolution of the ore-forming system from the high-temperature skarns to low-temperature argillisites. Skarns are the earliest metasomatic rocks. Their major rock-forming minerals are garnets of the grossular-andradite series, diopside, clinochlore, vesuvianite, and wollastonite. A decrease in temperature resulted in the replacement of skarns by medium-temperature quartz-sericite meta-somatites and then low-temperature argillisites. Their major rock-forming minerals are quartz and muscovite. The quartz-sericite metasomatites also contain subordinate carbonates with dominant Fe-bearing dolomite and accessory scheelite. Argillisites contain Ba-bearing orthoclase and baryte. The low-temperature ores host accessory prehnite, pumpellyite-(Mg), and talc. A diversity of gangue minerals in breccias is caused by both telescoping of ore-forming processes and mechanical contamination of breccias by rock-forming minerals of host rocks. It was found that some varieties of these rocks exhibit two or, less often, three successive assemblages of metasomatic minerals (Stepanov et al., 2017). Some minerals, such as Cr-spinels, geikielite, pyropha-nite, augite, monoclinic amphiboles, albite, orthoclase, etc. were mechanically emplaced into the breccia matrix during hydrothermal-explosive processes.
Conclusions
Although the open pit mining at the Vorontsovskoe deposit has been finished, the mineralogical potential of the deposit is far from being exhausted. Exploration drilling in 2017-2019 revealed a significant gold mineralization under the northern open pit. In 2020, the Polymetal Company conducted technical studies in order to determine the feasibility of the underground mining, as well as the open pit mining of oxidized ores in the western flank of the open pit. In 2022, the company planned to continue the geological exploration of neighboring promising areas. All this gives hope for the appearance of new mineralogical material, the study of which can yield interesting mineralogical findings at the deposit.
Acknowledgments
We are sincerely grateful to Igor Pekov, Vlad Gurzhiy, Elena Belogub, and Irina Melekestseva for valuable comments and editing that substantially improved the manuscript. We also acknowledge Nikita Chukanov for the IR spectroscopic study and assistance in the interpretation of Raman spectra of sulfo-salts, Leonid Pautov for the help in optical studies and measurement of reflectance spectra of vorontsovite and ferrovorontsovite, and Anastasia Kasatkina, Victor Levitskiy, Maria Milshina, and Tim Pashko for the photographing of minerals. We appreciate the help of the management of the Uralian Branch of the Polymetal Company: Director Andrey Novikov in assistance of field works and Chief geologist Andrey Gottman for providing samples with native arsenic.
The field works were partly supported by state contracts of the IGG UB RAS no. AAAA-A18-118052590032-6 and SU FRC MG UB RAS no. 07500880-22 nP.
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