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11тыс. га или 92,2% от площади земельного фонда страны [3,4].
В настоящее время в субъектах Российской Федерации продолжает уточняться правовой статус и принадлежность земель, формирующих землепользование хозяйствующего субъекта, в частности, земельной доли в составе сельскохозяйственного предприятия. В основном подобные уточнения наблюдаются на землях, переданных в самом начале земельной реформы предприятиям в коллективную (совместную или долевую) собственность, так как однозначно право собственности на земельную долю определяется только после регистрации этого права в соответствии с установленным законодательством порядком.
Таким образом, в России на протяжении уже почти 30 лет со дня начала земельной реформы, путём проб и ошибок фактически сформировались основы нового земельного строя, который характеризуют современная законодательно-нормативная база, многообразие форм собственности на землю, многоукладное и платное землепользование, обеспечение населения страны земельными участками,
современная система кадастра и регистрации прав на землю.
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4. Долматова Л. Г., Петрова И.А. Основные факторы государственного регулирования экономических отношений сельскохозяйственных предприятий // Вестник ЮРГТУ (НПИ). Социально-экономические науки. -2016. - №5.- С. 35-40
THE FIRST EXPERIENCE OF THE APPLICATION OF THE THERMOFORMS OF THE MERCURY IN THE INVESTIGATION OF THE ORE STRUCTURE IN SEDIMENTARY THICKNESS OF THE JUAN DE FUCA RIDGE
Luchsheva L.
Candidate of biological sciences, researcher of the Laboratory of volcanogenic-sedimentary and hydrothermal lithogenesisof the Geological Institute of the RAS, Moscow Konovalov Yu.
Candidate of geological and mineralogical sciences, researcher of the Laboratory of volcanogenic-sedimentary and hydrothermal Lithogenesis of the
Geological Institute of the RAS, Moscow
Kurnosov V.
Doctor of geological and mineralogical sciences, head of the Laboratory of volcanogenic-sedimentary and hydrothermal Lithogenesis of the
Geological Institute of the RAS, Moscow
Abstract
This article presents the results of studying the distribution of mercury concentrations and its thermoforms in sedimentary rocks of the active hydrothermal field "Dead Dog" in the Middle Valley (northern part of the Juan de Fuca Ridge). Sediment samples were taken from the core of the 858B hole drilled on the top of the sulfide hill in the zone of the ascending flow of hydrothermal fluid, a few meters from the source with a temperature of 276°C. The mercury content and its thermoforms were determined by atomic absorption spectrometry with thermal atom-ization. The highest concentrations of mercury in precipitation reach 10.3 ^g/g. Mercury in sediments is present in different thermoforms: free, chloride, physically and chemically sorbed, sulfide and isomorphous forms. In the sedimentary section of rocks three sulfided sedimentary layers were identified using mercury thermospectras, the composition of which depends on the degree of conservation of these layers from erosion.
Keywords: mercury; thermoforms of mercury; sulphide ores; methane; Middle Valley of the Juan de Fuca Ridge.
The amount of mercury on Earth is relatively small, but it is very disseminated.In the air and water environment, as well as in most rocks Always some amount of mercury is present. In geological systems, mercury is mostly in a dispersed state, it concentrates only in hydrotherms and can form even ore deposits [1]. Mercury is a good indicator of deep faults and hidden-
buried mercury and polymetallic ore deposits, as it refers to the most mobile "through" chemical elements
[2]. Mercury has the ability to form contrasting litho-chemical halos of dispersion around sulfide deposits
Hydrothermal processes are a powerful factor in the endogenous supply of mercury to the zone of hypergenesis. Therefore, recently, interest in the levels of mercury content and the forms of its presence in modern ore-forming hydrothermal systems has significantly increased. Recently, researchers have begun to use not only the concentrations of total mercury, but also its thermoforms to identify geochemical environments when solving geological and environmental problems
[4; 5; 6 et al.]. The study and identification of mercury thermoforms were first conducted by V.P. Fedorchuk [2]. Since the mid-1980s, thermoforms have become widely used to study rocks, ores, soils and bottom sediments [3; 7; 8; 9; 10]. The most detailed study of the thermoforms of mercury was conducted by V.L. Tau-son and colleagues in the rocks of the Aktash mercury deposit (Gorny Altai), when characterized by a high content of mercury [11].
130° 126° 122° W
Fig. 1. Schematic structural-tectonic position of the Middle Valley, Juan de Fuca Ridge, northeastern Pacific [12].
Materials and Methods
The task of our study with the use of thermoforms of mercury was to study the behavior of mercury in the region of the active hydrothermal field "Dead Dog" in the Middle Valley of the Juan de Fuca Ridge (Fig. 1). The Middle Valley is located within the East Pacific Rift System with the rate of spreading of 58 mm / year. As is well known, zones of active spreading within of the rifts of the mid-oceanic ridges are characterized by a widespread display of the process of mercury degassing of the Earth [13].
The analysis of mercury and its thermoforms was carried out by us at the Geological Institute of the Russian Academy of Sciences using atomic absorption spectrometry with thermal atomization on a RA-915 + mercury analyzer with a pyrolytic annexe RP-91S. A direct determination of mercury content without pre-
liminary mineralization and the use of additional reagents was carried out. To verify the correctness of the results obtained, a standard sample of GSO 2500-83 (SDPS-3) with a mercury concentration of 290 ng/g was used. The standard sample was analyzed at the beginning and at the end of each series of samples with an interval of no more than 2 hours, which is consistent with the recommendations of the analyzer manufacturer (SPC Lumex).
Thermoforms of mercury are determined using the original installation, which consists of a mercury analyzer RA-915+, a thermostat TPM-251, an recorder AC-4 (OWEN firm) and a thermometer TPHA (K) -K11.N.0.5x1 (NPK RELSIB). The selection of individual thermoforms of mercury was carried out under conditions of uniform gradual heating of rock samples to 600°C for 5 minutes with a gradient of 2 degrees/s.
To each form of mercury corresponds to an individual temperature threshold of exit maximum its concentration in the process of gradual heating of the samples. In connection with this feature of mercury, it was proposed to allocate corresponding its thermoforms. These thermoforms are not tied directly to specific minerals or chemicals, but its have specific temperature ranges of exit in the process of heating the samples. This is confirmed by experimental data for synthetic mercury compounds.
Thermoforms of mercury are conventionally called as elemental (SV), chloride (CL), physically
Table.
Temperatures of peaks of various forms of mercury in the synthesized mercury-containing minerals (according
to data on thermic atomic absorption spectrometry)
sorbed (FS), chemically sorbed (CS), sulfide (SF) and isomorphic (IZ) forms of mercury [11; 14]. Diagnostics of concentration peaks of individual thermoforms of mercury were carried out by comparing their temperature ranges of exit of maximum concentrations with those established for reference samples (Fig. 2). The reference form was FS mercury, which is usually quite reliably diagnosed, since it has very close temperature parameters for peak output for almost all studied rocks and minerals [11].
Thermoforms Temperature ( oC )
Tauson et al., 1994 Mashyanov et al., 2004
Elemental (Hg°) SV 150-160 80-150
Chloride (HgCl2) CL - 170-200
Physically sorbed FS 240-290 190-290
Chemically sorbed CS 250-320 -
Sulfide (HgS) SF 350-410 320-400
Isomorphic: 1 - in sulfides 2 - in quartz IZ 1 450-1000 400-600
IZ 2 >1000 400-1000
The curves of output of thermoforms of mercury have the form of parabolic peaks. These peaks were recorded in the form of thermograms in the coordinates of "absorption - T°C" into temperature range of 30-600°C. On thermograms, parabolic peaks of absorption corresponding to individual thermoforms were identified. The relative peak areas, proportional of the amounts of released individual thermoforms, were calculated graphically. The relative content and concentration of each individual thermoform of mercury in the thermospectras was calculated in accordance with its share in the total area of the analytical signal and in the concentration of mercury in the sample.
A detailed study of the distribution of mercury thermoforms was carried out in a hole (858B) drilled in the Middle Valley of the Juan de Fuca Ridge. This hole is located on top of one of the sulfide hills, directly in the zone of the upward flow of hydrothermal fluid. Near the hole was the mouth of a high-temperature hydrothermal source with a temperature of 276°C [12].
Directly from the core of the hole 858B, 14 samples of sediments were analyzed on the content of total mercury, as well as its thermoforms. In total, more than 250 samples of sedimentary and igneous rocks were taken from cores of several holes drilled in the area. In the samples was determined the content of mercury and calculated the its background content, which is 0.140 ^g / g, which is 3 times higher than clarke value. In 10% of the samples, abnormally high concentrations of mercury were detected (up to 10.30 ^g / g). In all samples of the sediments in which mercury was analyzed, the content of about 50 elements was also determined by X-ray structural analysis and ICP-MS.
Results and Discussion
In the section of the well, which was studied up to a depth of 38.37 m, we identified three sulfide layers in
the vertical profiles of the distribution of mercury and ore elements. These layers are abnormally enriched in mercury and in the following elements: Fe, S, Cu, Zn, Co, Pb, As, Se, Mo, Sb, Ag, Te, Au, as well as U and in other elements characteristic for hydrothermal sulfide deposits [15]. In the studied sedimentary layer, the mercury content varies from 0.05 to 10.3 ^g / g, which is almost 230 times higher its clarke. In the uppermost 1 st sulfide layer, located on the horizon of 11.0-12.3 m, the concentrations of mercury were abnormally high (from 1.03 ^g / g to 10.3 ^g/g). In the two lower sulfide layers, mercury concentrations were significantly lower: in the 2nd layer (hor. 31.6 m) - 0.24 ^g/g, in the 3rd layer (hor. 37.8 m) - 0.51 ^g/g.
The 1st sulfide layer has the richest sulfide mineralization, which is manifested mainly in two horizons (11.05 and 12.32 m). This layer is characterized by the highest concentrations of the main components of sulfide ores: iron (up to 42.8%) and sulfur (up to 35.5%), as well as high concentrations of a number of other ore elements: Zn, Cu, Pb, As, Se, Mo, Sb, Hg , Ag, Te, Au, U and etc. In this layer, the predominant forms of mercury are IZ (30-45%), SF (30-33%), and CS (1718%), the shares of the other thermoforms are much smaller.
The 2nd sulfide layer (hor. 31.55 m) is located in the brechirovanny part of the sedimentary thickness. Increased permeability of rocks could lead to intensive circulation of hydrothermal solutions and marine drainage waters. This led to the recrystallization of sulphide minerals and the gradual removal of soluble elements outside this layer. This layer, as well as the 1st sulfide layer, is characterized by abnormally high concentrations of Cu and Zn in the sediments. At the same time, the concentrations of other elements of sulfide mineral-
ization (As, Se, Mo, Sb, Pb, Ag, Hg, Te) were significantly lower here than in the 1st layer. In the sediments of the 2nd layer, the mercury concentration (0.24 ^g / g) is significantly lower than in the 1st layer, while the spectra of the thermoforms of mercury in these layers vary greatly among themselves. In the spectrum of the thermoforms of the 2nd layer, the IZ form of mercury completely disappeared, and the content of CS form (45.2%) and SF form (25.3%) was significantly increased.
The 3rd sulfide layer (hor. 37.8 m), as well as the first two sulfide layers, are characterized by abnormally high concentrations of Cu and Zn. In this layer, the concentrations of elements (Fe, S, As, Se, Mo, Sb, Pb, Ag, Hg, Te) is much lower than in the 1st layer, but noticeably higher than in the 2nd layer. In the sediments of
the 3rd layer, the mercury concentration (0.51 ^g / g) is significantly lower than in the 1st layer, but it are 2 times higher than in the 2nd layer. In the 3rd layer, there is a sharp predominance of sorption forms of mercury: FS (64%) and CS (27%), and the spectrum of the ther-moforms of mercury in this layer is almost similar to that in the 1st layer. In this layer IZ form (52%), CS form (28%) and SF (13%) forms of mercury are also prevailing.
It should be especially noted that we managed to distinguish the two lower layers of the sulfides (2nd and 3rd) into the sedimentary thickness studied by us based on the study of the distribution of concentrations of total mercury and its thermoforms.
Fig. 2. Thermospectras of mercury in precipitation samples from the sulfide layers of the sedimentary thickness
of hole 858B (Middle Valley, Juan de Fuca Range). A - 1st sulfide layer (sample 2950); B - 2nd sulfide layer (sample 2953); C - 3rd sulfide layer (sample 2954). Thermoforms of mercury: SV- elemental, CL - chloride, FS - physically sorbed, CS - chemically sorbed, SF -
sulfide, IZ - isomorphic.
During the initial study, these layers were not identified. These lower sulfide layers were formed, obviously, in earlier periods of ore genesis than the upper 1st sulfide layer. They apparently underwent significant high-temperature metamorphic changes that led to a significant decrease in the concentrations of mercury and a number of other ore elements.
Thus, on the basis of studying the thermjspectras of mercury in the studied sulfide layers, we made conclusions about the degree of their preservation from erosion. In our opinion, the 1st and 3rd sulfide layers have a fairly good preservation of ore deposits, since
the thermal spectra of mercury in them are almost identical. The second sulfide layer is, obviously, significantly permeable for drainage sea waters. This leads to the destruction and recrystallization of sulfide minerals, as evidenced by a significant change in the thermospec-tra of mercury in this layer.
The destruction of sulfide minerals is accompanied by their dissolution, the removal of a number of ore elements from them. We noted that outside the 2nd sulfide layer there is a significant concentration of some elements, in particular, uranium. Therefore, it can be considered that the levels of total mercury content and
thermospectras of its thermoforms are reliable geo-chemical indicators of sulphide ore formation processes.
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