pdf № 259, July

We have studied fluid inclusions in the quartz of recrystallized gold sulfide layers and in a pyrrhotine-quartz vein of the Golets Vysochayshy field confined to carboniferous shales of Riphean khomolkhinskaya suite. Methods of  homogenization, cryometry and Raman spectroscopy were used for the investigations. The study allowed estimating conditions of the metamorphogenic-hydrothermal stage of ore formation. The mineral formation proceeded in aqueous solutions with the salinity 7—13 wt. % NaCl eq., containing nitrogen, methane and carbon dioxide with a small amount of propane and ethane. The homogenization temperature of the fluid inclusions in the quartz of laminated sulfide segregations was 232—473 °C, usually within 310—370 °C; a higher homogenization temperature (up to 507 °C) was observed in the inclusions in a pyrrhotine-quartz vein. It was assumed that the recovered (CO₂/CH₄<0.3) methane-nitrogen fluids, generated in black shales, interacted with the abyssal oxidized carbon dioxide aqueous fluids in the mineralization zone.

Keywords: fluid inclusions, gold, carboniferous shales.

DOI: 10.19110/2221-1381-2016-7-3-9

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The results of mineralogical and geochemical studies of iron meteorite Big Dolguchan are discussed. The meteorite is characterized by taxitic structure, 85—90 % nickel-iron composition contains more than 50 microelements, abnormally enriched Pt, Rh, Ru, Ir, Tl, W, Pb, Mo, B, Re. Also the admixture of free isotopically light carbon is revealed. The mineral composition is determined by the iron-nickel intermetallic compounds and alloys, troilite unprecedented chemical and nominal composition of chromespinelides. For the first time in meteorites we discovered a silicon phase, which is probably composed of silicon hydrides or (and) lithium silicide. From the combination of microstructural and mineralogical and geochemical properties of the Big Dolguchan is to be attributed to a group of single Anomalies UNGR. 

Keywords: iron meteorite, microstructure, intermetallic compounds and alloys, nickel-iron, troilite, chromite, silicon phase.

DOI: 10.19110/2221-1381-2016-7-10-18

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The article presents the results of petrogeochemical studies of rocks of the Lower Proterozoic gneiss-migmatite Nyartin complex in the Subpolar Urals, the material composition of which is still relatively poorly investigated. The considered complex is composed of polymetamorphic formations; this makes the using of traditional petrographic and lithologic methods for identification of their primary nature very difficult or impossible. In this case, the decisive importance for establishing the primary substrate of metamorphites is their chemistry.

Reconstruction of the original composition of metamorphites was carried out, and the paleogeographic conditions of protolith formation were performed for the first time on the basis of interpretation of previously published papers on the chemical and mineralogical composition of rocks, and new petro- and geochemical data. It was found that the igneous rocks of andesite-basaltic set of tholeiite and calc-alkaline series were initial formations for orthometamorfites. Polymicticaleurolites, greywacke and quartz-feldspathic sandstones were substrate for metaterrigenous rocks. In turn, the igneous rocks of basic and acid composition as well as recycled sediments with different degrees of petrochemical maturity were original material for aleurolites and sandstones. The formation of volcanic-sedimentary substrate of the Nyartin metamorphites took place in the dry cold climate at quite strongly rugged topography.

Keywords: the Subpolar Urals, the Nyartin complex, lithogeochemistry, substrate of metamorphites.

DOI: 10.19110/2221-1381-2016-7-19-32

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The results of studying the composition of Lower Paleozoic metasandstones in the northwest of the Polar Urals have been summarized in the article. Geochemical features of these rocks were revealed, and sources of terrigenous material and conditions of sedimentation were suggested. With the help of geochemical diagrams three lithological varieties of metasandstones were distinguished and characterized. The association of volcanomictic metasandstones and underlying Upper Riphean mafic volcanic rocks was confirmed. We discovered that the micaceous metasandstones resembled those from Alkesvog Formation in the Polar Urals.

Keywords: metasandstones, chemical composition, detrital material, source area, sedimentation conditions.

DOI: 10.19110/2221-1381-2016-7-33-42

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The 3D geological model of the Crimean training ground is presented. The model represented a three-dimensional structural and tectonic wireframe mesh with thickness 700 m and area 90 sq. km and interpreted spatial relationship of MZ-KZ rocks and faults.

Keywords: 3D geological model, computer modeling, Crimean training geological ground.

DOI: 10.19110/2221-1381-2016-7-43-45

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The Upper Devonian — Lower Carboniferous stratigraphic interval of the North of Urals and Urals Foredeep is promising for search of hydrocarbons and other mineral deposits. So urgent is the establishment of a detailed stratigraphic framework and the identification of levels with the high correlation potential. Conodont biostratigraphic boundaries (expansa, praesulcata, sulcata, duplicata, sandbergi, quadruplicata, and isosticha zones) and global events (Dasberg, Hangenberg, and Lower Alum Shale) in the Upper Famennian — Tournaisian of the North Urals and Chernyshev Swell (Kozhim River section, Syvyu River section, Izyael River section and Malaya Usa River section) are characterized. As a result the levels having the highest correlation potential (base of the sulcata Zone, base of the quadruplicata Zone, transgressive phases of the Hangenberg Event and Lower Alum Shale Event) are identified. Detailed studies of the distribution of conodonts in the Devonian-Carboniferous boundary interval revealed that taxa Polygnathus purus Voges and Pseudopolygnathus primus Branson et Mehl begin its spread on the level of the first appearance of Siphonodella sulcata (Huddle). Consequently, they are on a par with Siphonodella sulcata (Huddle) can determine the position of the boundary between the systems in the sections of the North Urals and Chernyshev Swell.

Keywords: conodonts, Famennian, Tournaisian, correlation levels, biostratirgraphy, events.

DOI: 10.19110/2221-1381-2016-7-46-53

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