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Research subject. This article focuses on the geological structure of the northern part of the Pai-Khoi carbonate parautochthone.Materials and methods. The study was based on the data obtained on the key sections of the North-Western Pai-Khoi. Research methods included lithological and facies analysis, subsidence curves, reconstruction of the thermal maturity of deposits based on conodont alteration indexes, X-ray microtomography for determining porosity values.Results. The Upper Devonian–Carboniferous succession (ca. 900 m thick) is composed of the terrigenous and carbonate Pyrkov Fm. (Frasnian), carbonate Lymbadyakha Fm. (Famennian-Tournaisian), Bolvanskii Fm. (Visean-Bashkirian), and Hoiponganase Fm. and Reef Chaika (Moskovian-Kasimovian). The early Frasnian part of the succession was deposited in a shallow-water environment. In the Middle–Late Frasnian, the Korotaikha paleodepression and an isolated carbonate platform was formed on the shelf edge. Filling of the paleodepression was completed at the end of the Early Visean. In the Late Visean–Late Carboniferous, a carbonate platform (ramp) formed. A Middle Paleozoic paleogeothermal gradient reconstructed on the basis of conodont alteration indexes is much higher in the Pai-Khoi carbonate parautochthone than in the most of Pechora Plate regions. This is likely to have been caused by the tectonic activity of the plate border in the Late Carboniferous–Mesozoic. A downward decrease in open porosity (from 6% to 0.1%) is likely to have been associated with increased compaction and recrystallization of the carbonates.Conclusions. Famennian-Tournaisian carbonate formations of the Pai-Khoi carbonate parautochthone were deposited under the conditions of isolated platform environment; however, the Visean–Late Carboniferous deposits were formed in the outer ramp environment. The Late Devonian–Middle Carboniferous carbonate deposits of the Pai-Khoi parautochthone demonstrate an extremely low open porosity and a high thermal maturity. These properties, along with the pronounced faulting and folding of the rocks, significantly decrease petroleum-bearing prospects of these deposits.

Research subject. The Karabash ore district is a unique structural zone in the Ural folded system, formed at the joint of the Magnitogorsk and Tagil depressions. The uniqueness of this zone is associated with its specific formation conditions: a Paleozoic copper pyrite belt with a width of about 8 km was squeezed between two blocks of ancient metamorphic rocks. This zone features a classic copper-pyrite deposit represented by steeply dipping ore bodies, which were initially characterized by a gentle dip. Elucidation of the primary geological structure and tectonic evolution of the district presents a relevant research task.Materials and methods. A geological cross section of the Karabash district was studied. Particular attention was paid to interactions between Paleozoic volcanic and sedimentary rocks and ultramafic bodies, whose age was determined by the method of zircon U–Pb dating.Results. The age of ultramafic bodies in the Karabash district was found to be 430–440 million years. Serpentinite blend (mélange) zones having a width of 60m were discovered in the sites of contact between ultramafites and host rocks. Regularities in the location of these zones in the eastern and western parts of the district make them suitable horizon markers for constructing a geological cross section of the Karabash ore district.Conclusions. It is established that the Karabash district is represented by a monocline synclinal fold formed by contraction of primary horizontal layers in the direction from east to west. The formation of the Zolotaya Gora golden deposit located in the eastern limb of the synclinal fold was associated with tectonic contraction processes.

Research subject. The article sets out to investigate the change of the geodynamic regime from the island-arc type to the accretionary-collisional type in the Late Devonian–Early Carboniferous, which occurred as a result of 1) a collision between the Western part of the Magnitogorsk island arc and the Eastern margin of the East European continent and 2) its later coupling with the heterogeneous composite East Uralian terrain.Materials and methods. The content of petrogenic elements and microelements in the rocks of the Late Paleozoic island-arc complexes of the Magnitogorsk island arc were determined using XRF and ICP MS methods at the Laboratory of Physicochemical Research Methods of the Institute of Geology and Geochemistry, Ural Branch of the Russian Academy of Sciences. In addition, available publications on the composition and formation conditions of these complexes were reviewed.Results. It was found that, in the Late Devonian–Early Carboniferous period, the process of island-arc magmatism of the Magnitogorsk paleoarc was substituted with the formation of intraplate volcano-intrusive complexes. The island-arc magmageneration and its manifestations were controlled by a latitudinal linear zoning and different depths of formation of magmatic cameras, reflecting the self-consistency and spatial isolation of these events.Conclusion. Due to the intensifying collision, melts from different mantle sources were mixing, thus contaminating the island-arc rocks by intraplate (plume-dependent) magmas. According to the composition and concentrations of high-field strength and fluid-mobile chemical elements, suprasubductional fluids played an important role in the evolution of late-island arc magmatic series.

Research subject. This article is devoted to the formation features of the Ural-Timan-Paleo-Asian segment of Eurasia. Materials and methods. The research was based on the authors’ data and those obtained following a review of available publications on the geology of segmentation. The Timan region was investigated using the geological information obtained by V.G. Olovyanishnikov.Results. A geodynamic map of the Ural-Timan-Paleo-Asian segment with a scale of 1 : 2 500 000 was compiled, which allowed further research into the structure and formation of the north-western part of the Eurasian area. This part was found to be mostly composed of geodynamic associations of orogens, orogenic systems and orogenic belts of the Upper Proterozoic (Riphean) and Paleozoic time intervals, as well as by elements of the Mesozoic-Cenozoic neoplate. These processes were supplemented by the formation of tectonic systems of superimposed depressions and protoplate protrusions. The formation of orogens, orogenic systems and orogenic belts is associated with the development and subsequent transformation of paleooceanic basins under the conditions of accretion and collision. The terranes of the ancient continental crust also participated in the formation of the segment’s geodynamic elements, for which a typification scheme was proposed. The articles present new data on the formation conditions of the segment’s orogenic elements and the relationship of the orogeny with global reconstructions, including the problem of closing the surrounding oceanic space.

Study object. The role of strike-slip fault tectogenesis in magmatism of the large (North Eastern Primorye) fragment of the Eastern Sikhote-Alin volcano-plutonic belt (ESAVPB) is studied. Materials and methods. The materials of geological mapping and field geostructural thematic-line research are used. Study methods are based on the concept of the geostructural patterns being formed by lateral, namely, strike-slip movements of crustal blocks. Results. There is recognized the system of the NE-trending sinistral faults, whose activation taken place during two stages. The pre-Late-Cretaceous fold-and-strike-slip-fault (orogenic) stage is characterized by the widely developed fold system within the stratified formations covering active strike-slip faults of the pre-Mesozoic consolidated basement. By the Late Cretaceous, the strike-slip faults cut the fold system into narrow blocks, creating the preconditions for the strike-slip faults’ activation during the next destructionand-strike-slip-fault (riftogenic) stage (Late Cretaceous – Cenozoic). During the latter, the strike-slip faults were activated under transtension (strike slip with extension) with formation of volcano-tectonic extension structures (VTES) nearcrosswise the strike-slip faults. The VTES played, on the one hand, the role of magma-feeding channels. On the other hand, the extension caused preconditions for formation of the depression subsidences that accumulated large volumes of the volcanics covering and «crosslinking» the VTES, resulting in wide development of volcanic covers within the ESAVPB. Conclusion. The VTES’ opening is thereby the effect of lateral (strike-slip) displacements of continental geoblocks that is not consistent with a priori ideas of the development of the East Sikhote-Alin volcano-plutonic belt under the oceanic plates’ subduction. The resulting materials complement the formulations according to which the East Asian volcanic belt formed under the structural-and-dynamic conditions being caused by the evolution of the East Asian global strike-slip fault zone resulting from displacement of the Asian continent to the south-west under the Earth’s rotational geodynamics.

Subject. This paper presents the results of studies of the mechanism of primary oil migration in the boundary sediments of the late Jurassic (Bazhenov formation)–early Cretaceous (Achimov pack) on the example of the well 431Р of the Imilor field. Materias and methods. Based on the working hypothesis of fluid fracturing as the main mechanism of primary oil migration, using optical-petrographic analysis, supplemented by geochemical research methods, systems of interconnected microcracks in the Tithonian-lower Berriasian and early Valanginian deposits were studied. Results. It is established that the investigated cracks occurred in three stages: 1) formation of primary sedimentary-lithogenetic fissures as a result of dehydration of clays in the stage of diagenesis and hydraulic fractures in the implementation of the Achimov of terrigenous rocks; 2) partial healing of cracks with secondary minerals in the catagenesis; 3) restoration of patency of the cracks in the generation of large amounts of free hydrocarbons of protopetroleum. It is shown that the migration of hydrocarbons generated by the formation occurred both within the Bazhenov formation itself and through a system of interconnected cracks in the contact zone of the Bazhenov formation with the Achimov formation. Conclusion. A detailed study of the mechanism of oil migration allows us to expand our understanding of the reservoir properties of the oil column, which in the future will allow us to forecast the reservoir properties of the Bazhenov formation including in the zones of anomalous sections (for example, in the Kogalym region).

Subject of study. The article presents the results of study of trace elements (TEs) in sulfides of the main ore body (borehole 1T) and the northwestern ore body (borehole 200) of the Dergamysh cobalt-bearing massive sulfide deposit hosted in serpentinites (South Urals). Materials and methods. The chalcopyrite-pyrite-marcasite sandstones of the main ore body and pyrite-chalcopyrite-pyrrhotite “gravelites” of its northwestern satellite were studied with laser ablation with inductively coupled plasma. Results. The TE contents, distribution and mode of occurrence differ in sulfides of the main ore body and its northwestern satellite. In ores of the main ore body, most TEs (Ag, Sn, Mn, As, Co, Ni, Te, Pb, Au) accumulate in pyrite-1, pyrite-marcasite aggregates concentrate Tl and Bi, marcasite is a host to Mo and Sb, and chalcopyrite contains Zn, Se and Cd. Pyrite-2 is depleted in TEs relative to other sulfides. In sulfides of the northwestern satellite, most TEs are related to chalcopyrite (Bi, Te, Zn, Cd, Se, Pb, Au, Tl, Ni, Co). Tin accumulates in cubanite, As and Ni are hosted in pyrite-4, Ag, Mn and Mo are concentrated in pyrrhotite, Sb is typical of pyrite-3, and Co accumulates in pyrite-2. Conclusions. Based on the correlation analysis, it is shown that sulfides of the main ore body and its northwestern satellite are characterized by different mode of TE occurrences. The differences are explained by two main reasons: 1) “mafic” and “ultramafic” metal sources for sulfides of the main ore body and its northwestern satellite, respectively, and 2) different degree of diagenetic alteration of sulfides.

Subject of study. The features of the evolutionary changing of Gzhelian-Asselian conodonts are examined. Materials. The data on Ural and North American conodonts are used. Results. The cyclic type of change of the Pa-element morphology in the process of the evolutionary development of the representatives of the genus Streptognathodus is established. Morphological evolutionary trends of gradual development alternate with the periods of the rapid appearance of a group of the forms of original constitution. The species of this group are characterized by wide distribution and short lifetime. Such species are used as the markers of the boundaries of stratigraphic subdivisions. Lower boundary of Gzhelian is determined by the appearance of species of the group simulator; the species of group isolatus mark lower boundary of Asselian. Model of the ensemble evolution of the related species is used for explaining the directed change in the morphology of conodonts. The saltational appearance of the determined indication is explained by the phenomenon of evolutionary oscillations. Conclusion. We can make conclusion about the sexual multiplication of this group of the organisms according the established alternation of the periods of the slow and rapid morphological evolution of conodonts.

The object of research. At the top of the Upper Riphean-Vendian sedimentary sequence of the Bashkirian meganticlinorium (western and central parts of the named structure, corresponding to the stratotypical locality of Riphean) there is a series of fairly well-established hiatuses – the pre-Uk and pre-Bakeevo. One can also assume the existence of the pre-Uruk and pre-Basa hiatuses. During each of them, the thin-grained aluminosiliciclastic’s distribution systems could be subjected to one or another transformations. However, whether this is actually the case is still not entirely clear. To solve this problem, the lithogeochemical features of clayey rocks of the Inzer, Minyar, Uk, Bakeevo and Basa formations are analyzed. If we assume that the hiatuses are accompanied by restructuring of the provenances, then this can/should lead to the appearance of more fresh, previously not subject to weathering, rock complexes at the paleo-watersheds. This circumstance should cause a change in the lithochemical characteristics of the thin-grained aluminosiliciclastics entering to the sedimentation area. Methods. The analysis of the lithogeochemical features of clayey rocks is based on data on the content of the main rock-forming oxides (about 40 analyzes) and rare and trace elements (total of 70 analyzes). These data make it impossible to investigate the change in different lithogeochemical parameters of clayey rocks (for example, CIA, GM, K2O/Al2O3, or others) from the bottom upwards through the section of each of the formations listed above, therefore we operate with the averages for the formation values of such parameters taking into account the values their standard deviations. Results and conclusions. On the majority of the discriminant diagrams used by us, the figurative data points of the Basa Fm. mudstones occupy a position that to some extent differs from the position of the clayey rocks of other formations. The only lithostratigraphic subdivision in the part of the Upper Precambrian sedimentary sequence of the Bashkirian meganticlinorium under consideration, whose clayey rocks demonstrate a chemically noticeably less mature, compared to the underlying formations, is the Uk Fm. It may be thought that this is the result of the appearance of more fresh (less transformed by weathering) rock complexes at the provenances. The scales of the pre-Bakeevo and pre-Basa breaks, if they existed, were, most likely, noticeably less significant.

Object of study. The article was devoted to investigation of the depth structure of the Earth’s crust and upper mantle along the Mezen–Timan–Pechora seismic profile (MEZTIMPECH), crossing the southern parts of the Mezen syneclise, the Timan ridge and the Pechora syneclise. Total profile length was 525 km. Materials and methods. In the course of writing the article, the data obtained by performing seismic surveys using the earthquake exchange wave method were used. The processing involved seismic data using the methods of deep seismic sounding, reflected waves, a common depth point, a correlated method of refracted waves, and materials from well geophysical surveys. In interpreting the research results, generalizing models of the deep structure of the territory were employed. Research results. As a result of the interpretation of the records of the method of exchange waves of earthquakes and the subsequent mathematical modeling, a geological and geophysical section was constructed to a depth of about 100 km and a number of seismic boundaries were identified. The pivotal boundaries of the exchange were: Ф0 – the surface of the Riphean folded basement, Ф – the surface of the pre-Riphean crystalline basement, M – the surface of Mohorovich, identified with the roof of the upper mantle. Additionally, horizons K1–K4 – in the crust of the Earth, M1, M2 – in the upper mantle were traced. Four regional geoblocks were distinguished in the seismic section, differing in depth of the basement surface, the Moho sectionand the underlying structural features of the consolidated crust: the Kirov-Kazhim aulacogen, the Vychegda depression, the Timan ridge and the Pre-Ural downfold. Conclusions. The results of deep seismic studies reflected regional features of the structure of the Earth’s crust and were the basis for the construction of tectonic models of large geological objects.

Research subject. The object of the study is the Ulyuk-Bar gold deposit ore-bearing rocks, located in the Bashkir meganticlinorium (the Southern Urals). Methods. The article presents the first data on the distribution of rare earth elements (REE), platinum group elements (PGE) and Au, obtained by inductively coupled plasma mass spectrometry (ICP-MS) on “ELAN- 6100 DRC” and “Agilent 7700” with the use of the computer data processing program “TOTALQUANT”, which includes automatic accounting of isotopic and molecular overlays on the mass spectral analytical lines of the determined elements. The chemical composition of ore minerals (native gold, pyrite, pyrrhotite, gersdorfite, chalcopyrite, arsenopyrite, and galena) was determined using an REMMA-202M scanning electron microscope with an LZ-5 X-ray energy-dispersive spectrometer and detectors for secondary and reflected electrons. Results. As a result of the studies, the enrichment of heavy lanthanides from ore-bearing rocks of the Ulyuk-Bar deposit in comparison with the sandstones and shales of the Bolshoi Inzer Formation outside of the ore field was established. It is shown that the noble-metal geochemical specialization of ore-bearing sediments of the Bolshoi Inzer Formation of the Ulyuk-Bar deposit is similar in a number of parameters to rocks of the Mashak Formation of the Shatak complex, formed under the influence of Middle Riphean magmatism on sedimentary rocks of the upper layers of the earth’s crust. Based on the calculation of the age of the minerals thorium and uranium, according to the isotopic studies of Rb-Sr (996 ± 26 Ma) and K-Ar (676–706 Ma) methods and galena by the Pb-Pb method (950 Ma), it was established that mineralization was formed in two stages. The first of which is associated with tectono-thermal activation at the border of the Middle and Late Riphean, and the second was realized about 600 Ma ago. Conclusions. It is concluded that the REE-EPG-Au taxonomy of ore-bearing deposits of the Ulyuk-Bar deposit is due to the polychrony and polygenicity of ore formation processes associated with the Middle Riphean plume magmatism, manifested over a vast territory, and the Late Vendian dynamothermal collisional metamorphism.

Research objects. Paleozoic (Ordovician–Middle Devonian) volcanic-sedimentary complexes of the contiguous Sakmara and Mugodzharskaya structural zones of the Southern Urals, which have a paleo-oceanic and island-arc nature. Мaterials and methods.The work was carried out on the basis of many years of personal research of the author with the involvement of literature data on other folded zones of the Southern Urals. Main results. In the early Devonian, the first intense clustering of different facies complexes of rocks took place, which determined the tectonic face of the modern western part of the fold belt. The uniformity and set of Paleozoic formations in all structures of the Urals are maintained along its entire strike and are not repeated in neighboring zones.The drilling data showed the primary character of bedding of the rocks of the Upper Devonian Zilair Formation on the dislocated volcanogenic-sedimentary deposits of the Lower-Middle Paleozoic. Thrust contacts are observed only in the marginal parts of the zone. The almost textbook views on the cover bedding of the Kraka and Kempirsai hyperbasite massifs are in contradiction with the data on the presence of “roots” up to 4–8 km deep in them. By the beginning of the Devonian, the Kempirsai massif was located within the Sakmara zone and was “cross-linked” with the surrounding effusive rocks of the Middle Ordovician by gabbro-diabase dykes. According to the results of seismometric studies, features of similarity of the deep structure of the base of the Sakmara zone with the structure of the Magnitogorsk-Mugodzharskaya zone, which also revealed a melanocratic basement, have been established. Conclusions. The formed structural zones of the Southern Urals are distinguished by a set of rocks of the same age, their stratigraphic range, and the autonomy of feeding areas. These differences have survived to this day. All subsequent tectonic episodes, including the sharpening epochs, only complicated the appearance and structure of the Southern Urals, without changing the relative position of structures that arose in the Early Devonian. There was no transfer, swarming of rocks from one zone through another in any of the subsequent stages of compression. The Early Devonian stage was the first, but at the same time the most intense, which determined the tectonic face of the modern western part of the Urals.

Research subject . The Vorontsovskoe deposit belongs to gold deposits, in which gold is disseminated finely across carbonate-terrigenous rocks (Carlin-type). This study was aimed at identifying the sources of lead in various ore types (in skarn, jasperoid, tuff-sandstone and limestone breccia) and evaluating the role of magmatic rocks (apophises of Auerbakh intrusions and dykes of medium-basic composition) in the mineralization. M aterials and methods . Ore and rock samples for isotopic analysis were collected in the northern quarry of the deposit, as well as were retrieved from exploration holes. The lead isotopic composition was studied in the analytical centre Geoanalytic , Institute of Geology and Geochemistry of the Ural Branch of the Russian Academy of Sciences, using a mass spectrometer Neptune Plus on the basis of the TL N MC ICP MS method. Results. The lead isotopic composition of ores and igneous rocks indicates mixed mantle-crustal sources. The primary lead isotopic composition of igneous rocks corrected for the age of 400 Ma is characterized by a linear trend with wide variations in 207 Pb/ 204 Pb (15.6824–15.5182) and 206 Pb/ 204 Pb (18.1973–17.7707). The lamprophyre dykes feature the least radiogenic lead located between the evolutionary curves for the mantle and orogen in the Doe–Zartman model. The most radiogenic lead is typical of the granodiorite of the Auerbakh intrusion apophises. The analysis points of diorite porphyrite, gabbro-diorite and diorite dykes are located between the orogen and upper crust curves. The sulphide ores are characterized by lower variations in the primary lead isotopic composition compared to igneous rocks – 207 Pb/ 204 Pb (15.6009–15.5421) and 206 Pb/ 204 Pb (18.0434–17.8404). The most productive ores in tuff-sandstones and limestone breccias are characterized by a significant predominance of the crustal component over the mantle component. Their points in the diagram 207 Pb/ 204 Pb– 206 Pb/ 204 Pb are located between the curves for the orogen and the crustal source with µ 2 ( 238 U/ 204 Pb) = 9.74. Conclusion. Mantle lead in the dykes under study appears to reflect the nature of their parent magmas and may have been partially extracted by melts from the footwall mafic rocks containing pyrite ores. However, crustal lead is likely to have resulted from assimilating host rocks when magmatic melts reached the upper crust level. Crustal lead migrated with the metamorphic fluid formed by the heat action of the Auerbakh intrusion on sulphide-bearing volcano-sedimentary rocks. Mantle lead might have been transported by the fluid flow from a deepseated magmatic chamber.

Research subject. Limestones of the Mid-Carboniferous boundary interval of the Urals eastern slope (“Khudo-laz”, “Khudolaz-gully” and “Bolshoy Kizil” sections at the Southern Urals, as well as “Iset quarry” and “Lugovaya” sections in the Middle Urals) are considered. Methods. Carbon and oxygen isotopic composition in bulk samples was analyzed. Results. The carbon and oxygen isotopic composition in carbonate deposits of the Serpukhovian-Bashkirian boundary interval in the sections of the Southern and Middle Urals eastern slope was studied. It is shown that the value of δ 13 C in the most complete sections varies from 1.5 to 3.8‰, while δ 18 O – from 23.1 to 30.7‰. Conclusions. Variations in the carbon and oxygen isotopic composition are associated with both global and local events. In the East Uralian basins (northern periphery of Paleotethys), the shift in carbon isotopic composition of carbonate sediments appeared in the Late Serpukhovian. In some cases, this trend correlates with the positive excursion of δ 18 O, which is most likely associated with the global short-term cooling (glaciation).

Resarch subject. To investigate the epicentral area of the Katav-Ivanovsk earthquake (05.09.2018, M5.8), which has so far been the strongest seismic event in the Urals during the entire period of instrumental observations. The surface manifestation of the main earthquake shock, the development of the focal zone in time, as well as the deep structure and geodynamic characteristics of the area, were studied. Materials and methods . The methods of seismic catalog analysis and remote and archive geophysical data study were applied. The nature of centurial variations in the level of magnetic field and the manifestation of fault tectonics was studied using audio magnetic-telluric sounding (AMTS). The speed of mod ern vertical movements was assessed by monitoring the gravitational field. The temperature of water in the well at a depth of 100 m was monitored. The processing and re-interpretation of archival gravimetry and magnetometry data was aimed at identifying lineament systems and clarifying disruptive faults. Results. It is shown that the earthquake occurred in the area of reduced fragmentation of the geological environment and was accompanied by a natural decrease and disappearance of the local magnetic field anomaly of 300 nTl in 36 years. One year before the event, a prolonged increase in the number of weak earthquakes (R 500 km) was observed, followed by a slight levelling-off in the first half of 2018. Two months before the event, an increase in seismic activity was noted again followed by a slump one month before the even. In September, the main shock was registered, followed by a swarm of seismic events. Among the latter, there were 3 with a magnitude exceeding 4. At present, the seismic regime has stabilized at the long-term average level. An increase in the groundwater temperature at a rate of 0.02 °C per month is currently observed. C onclusions . An increase in the deepground temperature contributed to the demagnetization of magnetic inhomogeneity, as well as to an increase in (in addition to tectonic stresses) temperature stresses in the earth’s crust, which jointly caused the seismic event.

Research subject and methods . The work is based on a comparative study of the data obtained by the authors and those published in literature on U-Pb ID-TIMS and “in-situ” isotopic examination of zircons extracted from a number of Ural geological objects (volcanogenic rocks of the Mashak Formation of the Bashkir Meganticlinorium, granitoid massifs of the Northern part of the Uraltau Ridge, Kumba gabbro-norite massif Platinum-bearing belt), as well as Australian diorites and South African mafic xenoliths. Results. Since the methods of ID-TIMS (ID-MC-ICP/MS) and SIMS dating of zircon are fundamentally different, their advantages and disadvantages should be taken into account when solving the corresponding geochronological problems. Conclusions . U-Pb ID-TIMS (ID-MC-ICP/MS) methods allow the analysis of individual crystals, as well as their fragments, with an unprecedented level of uncertainty concerning age dating (up to 0.05%). The main drawback of the U-Pb SIMS method consists in a significant error when dating U-Pb (2–5%), which might disguise possible Pb losses (and / or U-contribution) and lead to appearance of artifacts when interpreting U-Pb zircon data. This, in turn, leads to the identification of non-existent stages of magmatism, metamorphism, false ideas about the length of evolutionary processes, etc. The use of U-Pb SIMS methods should be limited to solving geological problems that do not require a high accuracy of dating (i.e., allowing rough estimation) but involving the need to study a large number of samples and corresponding zircon grains. Such problems arise during examination of clastic material in the process of reconstructing sources and geological conditions of sedimentary basin formation. U-Pb SIMS methods can be used for studying the heterogeneity of zircon crystals having a complex structure under preliminary selection of materials for subsequent high-precision dating using U-Pb ID-TIMS and / or ID-MC-ICP/MS methods. The expansion of the number of laboratories using these high-precision methods seems to be the most important direction in the development of Russian isotope geochronology.

Research subject. The article presents the results of dating two dolerite dikes differing in geochemical features from a section along the Iset river in the area of Smolinskoe settlement (the Eastern zone of the Middle Urals). Materials and methods. The dating was performed by an U-Pb ID-TIMS technique for single zircon grains using an artificial 205Pb/235U tracer in the laboratory of geochronology and isotope geochemistry of the Geological Institute of the Kola Science Centre of the Russian Academy of Sciences. The lead isotopic composition and uranium and lead concentrations were measured using a Finnigan-MAT (RPQ) seven-channel mass spectrometer in dynamic mode using a secondary electron multiplier and RPQ quadrupole in ion counting mode. Results. The dikes were dated 330 ± 3 Ma and 240 ± 2 Ma. Conclusions. The research results indicate different ages of dolerite dikes developed within the Eastern zone of the Middle Urals. The oldest of the two established age levels corresponds to the Early Carboniferous era. This fact, along with the proximity of the dolerites to the petrochemical features of the basaltoids of the Early Carboniferous Beklenischevsky volcanic complex, allows these bodies to be considered as hypabyssal comagmates of these volcanics. The youngest obtained age level – Triassic – indicates that the introduction of some dolerite dikes was associated with the final phases of the trapp formation developed rarely within the eastern outskirts of the Urals and widely further east in the foundation (pre-Jurassic basement) of the West-Siberian Plate.

Research subject. The article presents the results of a study of sedimentation rate and physical properties of bottom sediments in the Angara reservoirs under controlled level regimes. Materials and methods. The work was based on the materials of fieldwork carried out by the author on the Angara reservoirs in 1972–2017 and open-access literature sources. The physical properties and particle size distribution of bottom sediments were determined by the standard methods of engineering geology. Results. It was found that the controlled level regime determines the time cycles of sedimentation in reservoirs, sources of sediment-forming material, sedimentation rate and ambiguity of the physical properties of bottom sediments. Conclusions. During transgressions, sands, coarse aleurites and fine-aleurite silts accumulate in reservoirs most intensively; however, during regressions, coarse aleurites and aleurite-clayey silts are accumulated. During transgressions, all types of sediments are characterised by the highest sediment density, sediment skeleton density and absorption capacity, while coarse aleurites and fine-aleurite silts exhibit high natural humidity levels. In addition, coarse aleurites are characterised by a high porosity, while fine-aleurite and aleurite-clayey silts are characterised by a high content of organic matter. During regressions, the porosity of sands, fine-aleurite and aleurite-clayey silts increases, the content of organic matter in sands and coarse aleurites increases, and all types of sediments become more saturated with carbonates.

Research subject. The isotopic composition (Pb-Pb, Sm-Nd, Rb-Sr, Os/Os, Hf/Hf, 3 He/4 He, etc.) of magmatic complexes and ore-magmatic systems (OMS) of two ore clusters (Kupolsky and Ilirneysky) located in the subpolar Western Chukotka was studied. These ore clusters differ from each other both in their structural position and the age of their magmatic complexes, within which the largest deposits of Au-Ag type are known. Materials and methods. The Pb-Pb, Rb-Sr, SmNd, Re-Os, Lu-Hf, 3 He/4 He, 40Ar/36Ar and sulphur isotopic systems were studied at the VSEGEI centre for isotopic studies (St. Petersburg), as well as at the Institute of Geology, Geochemistry and Ore Deposits (IGEM, Moscow) and the Laboratory of Stable Isotopes of the Far Eastern Geological Institute (FEGI, Vladivostok). Re and Os were measured using an ELEMENT-2 inductively coupled plasma single-collector mass spectrometer. Sulphur isotopic ratios were measured using a Finnigan MAT 253 isotope mass spectrometer. Results and conclusions. On the basis of the isotope-geochemical data obtained, an assumption was made that various deep sources participated in the magma generation, and the differentiated composition of late melts may reflect the melting processes of the crust upper horizons. When comparing the data on the magmatism of the Ilirneysky and Kupolsky ore clusters, a different degree of crustal rock influence on melt generation was revealed. The Kupolsky ore cluster is characterised by a large influence of mantle sources in intraplate magmatism associated with ore formation processes. This is likely to have determined a greater amount of mineralisation in the Kupolsky cluster compared to the Ilirneysky ore cluster.

Research subject . The paper describes large tectonic zones in the North Caucasus, which can be classified as deep faults according to a number of features. Among these formations are the Ancient axial fault zone earlier described by G.D. Azh-girei, which we attributed to Hercynian structures (with the presence of pre-Paleozoic); the Indosinian axial fault zone and the Main Caucasian fault (overthrust). Materials and methods . The Ancient axial fault zone is considered as a suture zone, which arose as a result of Varis с an (Hercynian) folding during the interaction of the Transcaucasian and East European tectonic plates (EETP). The Indosinian axial fault zone contains fragments of Variscan nappes and neoautochthonous deposits of the same age. Results. The surface manifestation of the Indosinian axial fault zone was a tectonic-formational zone of the Front Range, which is located at the junction, on one side, with the newly formed hard crystalline massif crust at the site of the Ancient zone (Main Range), and, on the other side, with EETP. This zone continued to be active later, during the Cimmerian and Alpine tectonic events. At the same time, the formation of new granite magmatic melts could occur. The driving mechanism is assumed to have been opposite undercrust convection flows. Although there are conflicting views on the Main Caucasian fault, it seems clear that this was a deep-seated and magma-producing zone at the pre-Callovian time. This fault is likely to have been formed as a consequence of the intraplate subduction, which is continuing at present. Conclusions. The presence of hyperbasite bodies in the fault zones under consideration is not a sign of their depth in the Caucasus. In the present structure, the mixtite zone lying under the flysch of the southern slope of the Greater Caucasus and overlapping the Transcaucasian massif can be considered as a large collision line currently under development. Some other faults present in the region, which are supposed to be deep, have also been considered.

Research subject . The article presents the results of investigating calcite lenses with a cone-in-cone structure from Middle Devonian clay terrigenous deposits in the Middle Timan. Methods. The investigation of petrographic thin-sections was carried out using a polarizing microscope Nikon eclipse LV100 ND equipped with a Nikon DS Fi2 camera. Polished sections etched with HCl were examined using a scanning electronic microscope JSM-6400 Jeol with a power dispersive spectrometer ISIS Link and a wave spectrometer Microspec. The decomposition of carbonates and the measurement of isotope carbon composition in the mode of continuous helium stream were carried out using a ThermoFisher Scientific analytical complex. Results. It is established that the investigated calcite bodies consists of mosaic block crystals having a drusy structure. Calcite is characterized by abnormally low values S 13 C carb - up to -23.5 %o. Clay films and soapstone inclusions were studied in detail. The formation mechanism of the saw-tooth profile of the upper bound of these inclusions was determined, which consists in the local substitution of alumosilicates with calcite under the maintenance of their relic layered texture. Conclusions. A new version of the crystallization model of carbonate body genesis with a cone-in-cone structure is proposed.

Research subject. In this research, volcanoplutonic formations (VPF) in the Baleisky ore node (BON) consisting of intrusions of the Amudzhikan-Shakhtama complex (J2-3) and comagmatic effusions of the Shadaron series (J2-3) were investigated.Methods. Investigations were carried out in the analytical center of the SB RAS Geological (Ulan-Ude). Silicate analysis was performed by the conventional method. Ore and rare elements were determined by the RFA method. Rare earth elements were detected using the ASP-AES method.Results. It was determined that VPF in the BON has a zonal structure. In the central parts of the BON, granite rods of the Amudzhikan-Shakhtama complex (J2-3) are located. Further, moving from the central BON parts towards its periphery, a belt of small intrusions of the Amudzhikan-Shakhtama complex (stocks of monzonite diorites, granodiorites, dikes of diorite porphyrites, lamprophyres) is located. The majority of gold deposits and ore occurrences are confined to this zone. The peripheral parts of the BON feature volcanogenic sedimentary deposits of the Shadaron series (J2-3). In composition, these deposits correspond to island-arc and post-col-lisional formations. It is shown that the intrusions of the Amudzhikan-Shakhtama complex correspond to high-potassium calc-alkaline series.Conclusions. It was found that the magmatic melts of the Mesozoic ore-bearing intrusions located in the Baleisky deposit area are more differentiated and located at lower depths compared to the rocks of similar composition in other BON parts.

Research subject. 14 samples of limestone and one sample of carbonate-siliciclastic rock from siliciclastic-carbonate deposits of the Upper Riphean Uk Formation (the Southern Urals) were studied.Methods. Mineral and chemical composition of the samples were determined; the main tool for detecting the concentrations of trace elements was the ICPMS method. X-ray diffraction analysis was carried out using a Shimadzu XRD-7000 diffractometer, the content of major (rock-forming) oxides in bulk samples was established by X-ray fluorescence spectrometry on the SRM-35 and Shimadzu XRF 1800 spectrometers. Microelement composition of bulk samples and acidic leachates obtained with using acetic (10%), nitric (36%) and hydrochloric (17%) acids was determined on a Perkin Elmer ELAN 9000 spectrometer.Results. The distribution of lithophile, rare-earth and a number of other elements (Sr, Ni, U) both in bulk samples and in acidic leachates was analyzed. The main carrier phases of these elements were revealed.Conclusions. 1. The use of any listed acids leads to the non-carbonate component entering the solution, including contamination of the “carbonate” leachates by lithophile elements. In particular, a transition Rb, Zr, Li, Th, Ti, Sc to leachates was noted. This process is most active in nitric and hydrochloric acids, less intensive in acetic acid. 2. Among the carriers of rare earth elements (REE) in the studied rocks are clays (1), accessory minerals (2), including phosphate-bearing grains, secondary carbonate phases represented by dolomite and, possibly (3), finely disseminated iron and manganese (oxy)hydroxides (4). It is assumed that the REE pattern in limestones is determined by the content of the epigenetic dolomite. The contribution of lanthanides bound in the sedimentary calcite crystal lattice in the total REE pattern is rather large only in relatively “pure” limestones. However, the use of acids with such concentrations did not allow to obtain a leachate, which the REE pattern with high probability corresponds to the distribution of REE in the Uk time seawater. But acetic acid is more effective for achieving this goal than the others. 3. In addition to Sr, sedimentary calcite also contains Ni and U.

Research subject. This study was devoted to magmatic complexes in Northwestern Chukotka associated with the largest gold and silver deposits across Kupol’skii (Kupol field) and Ilirnei (Dvoinoe and September fields) ore junctions. Materials and methods. The petrogenic elements of ore-containing igneous rocks were determined using a spectrometer ICAP 6500Duo (USA). An elemental analysis of igneous and ore samples was performed by inductively coupled plasma spectrometry (ICP-MS). The age was determined by zircons (SHRIMP-II, VSEGEI isotope research center, St. Petersburg) using a laser ablation system NWR-213 (USA). Results. New information concerning the dating of magmatic complexes and gold-bearing magmatic systems in the ore junctions under study was obtained. It was established that the manifestations of magmatism in the Kupol and Ilirnei ore junctions differ in terms of the main phase formation age. The age of the Ilirnei ore junction, which is represented by large-volume intrusions of granitoids, leucogranites and volcanites of medium-basic composition, was determined to be 124–114 Ma. The age of mineralization, which is associated with later magmatism phases – small intrusions and a dike complex of predominantly granodiorite composition –, was estimated to be (93– 92) ± 2.0 Ma. In the Kupol ore junction, the magmatism associated with mineralization was dated 91.0 ± 1.4 Ma, while the age of rhyolite dikes containing mineralization was estimated to be 88.9–89.0 Ma.Conclusion. The results of the RMS analysis of the Kupol and Ilirney ore junctions suggest that ore formation in this region was connected with a single stage of activation of deep processes and mantle-crust interaction with participation of deep (mantle) fluids.

Research subject. The Prikolyma terrain located in the Northeastern part ofRussia constitutes a long-lived Precambrian thrust-faulted structure hosting numerous Cu, Pb and Zn deposits of different types.Materials and methods. The mineralization of the terrain was examined during a course of research and exploration works over the 2007–2012. The rock geochemistry was studied using ICP-OES analysis at the Stuart Geochemistry and Essay laboratory (Moscow). The microprobe analysis of minerals was carried out at the facilities of the Far Eastern Branch of the Russian Academy of Sciences (Magadan) using a Camebax X-ray microanalyzer. The isotopic ratios of sulphur in sulphides were measured using a Finnigan MAT 253 isotope mass spectrometer.Results. The porphyry-copper deposit Nevidimka is represented by skarns and sulphide-quartz stockworks embedded in porphyry granites. The vein deposits Opyt and Glukhoye constitute sulphide-carbonate-quartz veins, the composition of which corresponds to copper-polymetallic ores of the peripheral parts of the copper-porphyry formation. These deposits feature a similar geochemistry and composition of sulphides and sulphur isotopes, which is characteristic of the Riphean complexes of the Prikolyma terrain. The stratiform Pb-Zn veins Nadezhda-3 and Khaya enclosed in Proterozoic dolomites represent parallel-bedding disseminated sulphides. The composition of these ores indicates their diagenetic origin. Tne stratiform copper deposit Oroyok is embedded in Proterozoic shales and can be referred to sediment-hosted copper deposits of a transgressive type.Conclusions. The diversity of Cu-Pb-Zn mineralization types in the Prikolyma terrain is established to have resulted from multiple cyclic changes of the geodynamic ore formation regime. During each such cycle, syngenetic mineralization was followed first by epigenetic and then by vein mineralization. The mobile, thrust-faulted structure caused repeated rejuvenation of ores, which inherited the geochemical features of hosting rocks.

Research subject. This article presents new data on the content of rhenium (Re), selenium (Se) and a number of other rare elements in the rocks of the Gorodishi section located in the Central part of the Volga basin shale (upper Jurassic) in the South-East of the Russian plate. In this section, rocks are rich in organic matter (15–37 % wt in oil shale) and contain layers of oil shale with a thickness of up to0.7 m.Materials and methods. The description and layer-by-layer testing of the Gorodishchi section was performed. Sulphides were isolated from two samples of carbonaceous shale for subsequent analysis. In the selected samples and isolated sulphides, the contents of Re, Se and a number of rare elements were determined at the VSEGEI central analytical laboratory. For the first time, the chemical composition of the samples was determined by ISP-MS using an Agilent 7700h device.Results. Oil shale samples demonstrated the highest concentration of Re and Se, with the concentration of Re and Se being on average 0.13 g/t (ranging from 0.09 to 0.19) and 10.39 g/t (from 6.54 to 12.4), respectively. A statistical analysis of the data obtained (using principal component factor analysis) revealed a close relationship of Re and Se both with the rock organic matter and with Cu, Cd, U, Ag.Conclusions. Anomalously high concentrations of Se and high concentrations of Re revealed in the oil shale of the section under study testifies to the need for specialized mineralogical and geochemical studies of the upper Jurassic carbon shale of the Central part of the Volga basin shale in terms of Re and Se content.

Research subject. The metamorphic ultramafites of the Kalninsky and Ergaksky massifs located in the northeastern part of Western Sayan (Russia) constitute the Kurtushibinsky ophiolite belt. These rocks are considered to be potentially interesting as bearing chromium and noble metals, which fact determines the relevance of this research.Materials and methods. Thin and polished sections of silicate and ore minerals from the ultramafic rocks under study were investigated using a polarizing microscope AxioScop, Carl Zeiss. The chemical composition of minerals was determined by the method of X-ray spectrum microanalysis using a scanning electron microscope Tescan Vega II LMU equipped with an energy-dispersive spectrometer INCA Energy 350 and a wave-dispersive spectrometer INCA Wave 700. The petrochemical composition of the rocks was studied by the methods of XRF analysis using an X-ray fluorescence energy-dispersive spectrometer Oxford ED-2000. A quantitative ICP-MS analysis was carried out using an Agilent 7500 spectrometer.Results. The massifs are found to be composed of dunites and harzburgites, which were formed during an uneven depletion of the mantle. As a result of depyroxenization, the ultramafites were enriched with chromospinelides. Subsequent intense plastic deformations contributed to their segregation into ore bodies. Regenerated olivinites predominate in the northern part of the Ergaksky massif. The microstructural features of ultramafites and the composition of minerals indicate them to have been subjected to inhomogeneous high-temperature plastic deformations, which occurred during their migration in the upper mantle and crust.Conclusions. The petrochemical studies have shown that the ultramafites of the Ergaksky massif are least depleted, frequently featuring clinopyroxene. The most depleted ultramafites of the Kalninsky massif are characterized by a more extensive distribution of dunites, the absence of clinopyroxene and lower contents of REE and rare elements in comparison with the ultramafites of the Ergaksky massif. The obtained geochemical data indicate a fluid-magmatic effect of boninite melts on depleted ultramafites, which apparently occurred under mantle conditions over the subduction zone and consequently led to their enrichment with incompatible LREE (La, Ce) and Sr, Zr and Hf, as well as to the formation of high-chromium chromitites.

Research subject. The idea of forecasting fluid-dynamical parameters is based on the views connecting the processes of sedimentation, tectonogenesis and fluid flows into an active fluid-dynamical model of the “sedimentary cover–basement” system. In such models, main fluid-dynamical parameters of oil and gas collectors, i.e. penetration and the vector of the fluid flow, are functionally connected with the components of the current state of the rock massif having a discrete (block) structure. These parameters can be calculated using DFM-interpretation technology developed by the authors in their previous works.Materials and methods. For the first time, DFM results are provided for the Yamal Novoportovsky oiland gas-condensing deposit. Here, the paleozoic basement stripped at a depth of 2700–3200 m is largely represented by metamorphic schists and marbled limestones. The basement has been covered by sediments and a platform cover since the early Jurassic age. The forecast of parameters describing modern geodynamical processes was performed on the basis of a comprehensive tectonophysical analysis of major geological and geophysical data.Results. The main axes of the neo-tectonic activity of the plate complex break the area under study into a quite regular block system that reflects a right-sided shift of fundamental blocks, that, in its turn predetermines the block shift in plate complex with the turn of the shift axis by 30 degrees. The most significant oil and gas holes in terms of influx demonstrate a connection with the described scheme of block activity. Thus, practically all high-debit boreholes were drilled in active axial zones.Conclusion. The proposed scheme of block activity satisfies the general principles of geodynamics. The developed model of abnormal pressure estimations by main productive intervals shows a good agreement with the distribution oiland gas boreholes in terms of productivity. Contact zones of active blocks present a particular interest from the standpoint of selecting the location of high-debit boreholes. These zones should be taken into account when developing new oil and gas deposits.

Research subject. This study was aimed at examining the strike-slip related tectogenesis of the Asia-Pacific transition zone (APTZ).Materials and methods. The research was based on the materials collected by the author during long-term fieldwork across the territories of Primorye, Khabarovsk Krai and, partly,Vietnam. Extensive materials on the topic of the APTZ tectogenesis published by researchers fromRussia,China andJapan were analysed. Investigations involved the study of structural and kinematic assemblages representing the forms, directions and time of crustal mass flows under the strike-slip related tectogenesis of the East Asian global strike-slip fault zone (EAGSSFZ).Results. The EAGSSFZ consists of three transit strike-slip fault systems (zones) playing the role of the APTZ basic deep fault structures. Its master system (MS) is NNE (25–30°) trending longitudinally to theAsia edge. The MS is bordered by diagonal NE 50–70° trending near-continental and meridional near-oceanic EAGSSFZ systems. The MS controls the East Asian volcano-plutonic belt (EAVPB), demarcating the APTZ into internal (near-continental) and external (near-oceanic) zones. Two stages of the strike-slip related tectogenesis were established: orogenic-constructive (Jurassic–to–Late-Cretaceous) and riftogenic-destructive (Late Cretaceous–to–Cenozoic). The riftogenic destruction broke the previously formed orogenic foldedthrust structures, thus causing the EAVPB magmatic succession from intracrustal intrusions (Early Cretaceous) to volcanics (Late-Cretaceous-to-Cenozoic). An increase in the crustal destruction during the end of Cretaceous to Cenozoic resulted in the formation of epicontinental sedimentary basins and deep-sea riftogenic depressions of marginal seas. The structure-forming flow of the APTZ crustal masses occurred in the SSW 180–250° direction being opposite and obliquely opposite towards the NNW subduction direction of oceanic plates.Conclusion. The kinematic disconformity as well as the coincidence of the continental crust flow (plate flows) with the direction of inertial-and-equator-oriented forces allowed the author to determine the structuring of the transition zone as a process independent of the geodynamics of oceanic plates and subordinate to the rotational geodynamics of the non-uniformly rotating Earth.

Research subject. In this research, we studied lenses, nodules and interlayers of granulated quartz, which are located in amphibolites and shales in the eastern part of the Ufalei gneso-amphibolite complex. Materials and methods . Petrographic features of the quartz bodies from garnet-mica, two-mica, garnet-mica and tourmaline-garnet-mica schists and amphibolites were studied using optical spectroscopy on an Axiolab, Olympus BX50 misrospope. The surface morphology of quartz chips was examined using a Tescan Vega 3 Sbu scanning electron microscope equipped with an Oxford Instruments X-act energy dispersive spectrometer. The elemental composition of the initial and deeply enriched quartz concentrates was determined using a Varian-720-ES optical emission spectrometer with inductively coupled plasma. IR spectra were recorded by a Nicolet-6700 Thermo Scientific infrared Fourier spectrometer. The spectra were simulated by superposition of Gaussian lines using the Peakfit program. The surfacing of quartz glasses from a deeply enriched concentrate was carried out using a modernized GRANAT-2M growth installation under argon atmosphere. Results. Quartz interlayers, lenses and nodules with a thickness of 0.5—1.0 to 1.5—3.0 m are formed by fine-medium or coarse-grained, transparent or translucent granulated quartz. In most cases, quartz bodies exhibit a heterogeneous structure, being intensely blocked and deformed in some places. The quartz under study is characterized by low concentrations of water-containing defects and impurity elements. When conducting deep enrichment of quartz grains, the results obtained are comparable to Unimin IOTA quartz. High quality characteristics of quartz are determined by the conditions of its formation and recrystallization processes, during which the transport of mineral impurities into the intergranular space occurred. Conclusions. Lenses, nodules and interlayers of granulated quartz in the eastern part of the Ufalei gnesovo-amphibolite complex are promising raw materials for the production of high-quality quartz concentrates.

Research subject . In this research, we carried out a series of mineralogical, petrological and geochemical studies to investigate ore zones present in the Kusa ilmenite-magnetite deposit located within the boundaries of a similarly-named laminated gabbro massif. Here, ore bodies occur at various intrusion horizons among laminated apogabbroid amphibolites of a different basicity. In the intrusion section, the composition of halogens (Cl, F) in co-existing fluid-bearing minerals (apatite, am-phibole, staurolite) was analyzed. Materials and methods . In order to investigate the composition of mineral samples, their polished sections were examined using an electronic-microprobe analyzer JXA-5. The content of petrogenic and microelement components (CRF and ICP-MS methods) in the rock and ore samples was determined using the facilities of the Laboratory of Physical and Chemical methods, UBRAS Institute of Geology and Geochemisty. Results. It is established that the content of Cl and F in the apatite, amphibole and staurolite under study, as well as the chemical composition of ilmenite, magnetite, and hombombite components, depend on the position of the ore bodies in the intrusion. Thus, the apatites from the near-ore rocks in the central part of the deposit showed the highest Cl concentrations of up to 4.1%, while those located in the near-contact parts of the intrusion demonstrated a much lower Cl content of 2%. The central ore-bearing zone having the maximal Cl content features the largest formation of ore bodies, which (including magnetite) contain higher amounts of Fe 2 O 3 , Cr and V The presence of fluid-bearing minerals (apatite, scapolite, etc.) with high chlorine concentrations of up to 2.44% is this deposit is established. Conclusions. The identified peculiarities of halogen distribution in the apatite of bipyroxene gabbro, as well as the inheritance of relations TiO 2 /FeO in bipyroxene gabbro, in massive magnetite-ilmenite ores and in near-ore rocks point to a single magmatic source of these formations.

Object of research. The mathematical apparatus of the theory of fractals and the algorithms developed within its framework are used to assess the statistical self-similarity of the fields of epicenter earthquakes in the Baikal region. Materials and methods . The solution is implemented on numerical models and at three hierarchical levels of the lithosphere of the region. A modified method for determining the fractal dimension is applied, when the scaling data are approximated uniformly for territories of various shapes and sizes, subject to the maximum coefficient of pair linear correlation of the function lnN = f(lnr). Numerical implementations of epicentral field models in the form of a “Koch snowflake” and “Sierpinski carpet” confirmed the advantage of the method in conditions of limited data arrays used. Results . Seismicity reflects the process of fault formation in the lithosphere, and the use of the modified method allows one to obtain more accurate parameters of the state of the fault structure of the lithosphere from the field of epicenters of earthquakes in the Baikal region. The main influence on the assessment of the indicator is provided by two interrelated factors: the growth of instrumental data over time and the geometry of the distribution of earthquake epicenters over the territory. Using the maximum correlation coefficient to estimate the self-similarity of the field of epicenters of earthquakes in the Baikal region allows us to significantly refine the magnitude of the self-similarity index - the difference between the self-similarity index (D 0 ≈ 1.70) and the cell dimension (D 0 ≈ 1.58) significantly exceeds three standard deviations. Findings. The applied method has a particular advantage with a small amount of initial data and can significantly improve the assessment of the self-similarity index in conditions of a limited duration of instrumental monitoring of earthquakes. In the absence of reliable data on the deep structure of the fault-block geomedium, the approach used and the results obtained contribute to the understanding of modern geodynamics and seismotectonics of the lithosphere of the Baikal region by analyzing the fault structure of the territories through the fractal dimension of the earthquake epicenter fields. In practical terms, information on monitoring the state of the fault structure of the lithosphere according to earthquake data can be used to characterize the seismic situation and the danger in industrial and civil construction areas.

Background . Any exploration work involves difficulties associated with a rapid assessment of the development prospects of the discovered ore occurrences, flanks and deep horizons of the exploited fields, new vein bodies within the known ore fields and nodes. Under these conditions, knowledge of the genetic models of formation of gold and crystal mineralization, genetically associated with quartz veins, gains a particular importance. Aim. There is a widespread opinion that the presence of industrially applicable crystal is characteristic only of barren quartz veins. As a result, it is such formations that attract the interest of researchers searching for deposits of rock crystal. However, a large number of ore minerals have been found in the crystal-bearing quartz-vein deposits in the Urals, both in the vein bodies and in the crystal cavities. Results. The analysis of a large amount of factual material carried out to reveal regularities of location of quartz-vein formations in the Ural deposits of crystal-like and gold mineralization testifies to the confinement of quartz-vein fields to suture zones, representing narrow extended tectonic ensembles of a complex geological structure, genetically and spatially associated with long-lived faults of deep laying. The formation of quartz veins refers only to certain stages of the deposit development, while the deposits themselves are always confined to certain structural elements. These structural elements determine the subsequent formation of ore fields, which frequently undergo significant transformations. Conclusions. The metamorphic and metasomatic zonality, various thermodynamic conditions of formation are manifested in the typomorphic features of vein quartz: its internal structure, chemical purity, light transmission, presence of microdefects. These features reflect the peculiarities of quartz genesis and can be used as criteria for forecasting and evaluation of geological objects, particularly during initial stages of the exploration work.

Research subject. The Kazakhstan (Kazakh-Kyrgyz) paleocontinent attracts much research attention. In this article, we present data on the tectonic structure of the Early Paleozoic Kokchetau-Issykkul sialic terrain. Materials and methods . The geodynamic position of the Kokchetau-Issykkul terrain was determined by analysing samples of Ordovician rocks collected across 11 sites using the paleomagnetism method. Thus, we studied the paleomagnetism of red sandstones, siltstones, tuffaceous siltstones and basalts, as well as that of andesite and tuffaceous rocks in marine sediments, which affiliation to different Ordovician formations was established on the basis of trilobite, brachiopod, conodont and graptolite fauna. Results. Early Paleozoic rocks are exposed in the northern part of the studied terrain (Kokchetau district) and in the Issyk-Kul region, which covers southern Kazakhstan, northern Kyrgyzstan and western Xinjiang. The sutures of Chistopol-Terskei and Iradir-Ili ocean basins serving as the boundaries of the Kokchetau-Issykkul terrain are located in the allochthonius position. A multi-storey system of napes composed of pre-Paleozoic and Early Paleozoic rocks of the oceanic crust, volcanic oceanic island arcs and continental slope were studied near the Terskei margin of the terrain. This system of napes is covered by sediments containing graptolites of the Floian-Darriwilian age. Subduction-related volcanism near this margin of the terrain is of the Darriwilian and Sandbian age, while I-type granites are of the Darriwilian age. The over-thrusting of the Iladyr-Ili oceanic crust on the Ili border of the terrain also occurred in the middle Ordovician. Subduction-related mag-matism occurred here in the Late Darriwilian and Sandbian periods. Conclusion. The conducted studies testify to the geodynamics of the region. In the Early and Middle Ordovician, the Kokchetau-Issykkul terrain was a sialic volcanic arc separated from other sialic terrains by ocean basins. In the Middle Ordovician, the counter subduction of the oceanic crust under the Kokchetau-Issykkul island arc occurred. This process led to the closure of the Chistopol-Terskei and Iradir-Ili ocean basins in Middle Ordovician and to the formation the Kazakhstan continent by the collision of the Early Paleozoic sialic terrains and oceanic island arcs. According to the study of the paleomagnetism of Ordovician rocks in the Kokchetau-Issykkul island, the position of the middle part of this arc is determined to be at the paleogeographic latitude of 9.1 ± 5.4°.

Research subject. The article presents results of mineralogical and geochemical investigation of albite-bearing granites with high concentrations of trace elements located in the Western Trans-Baikal region. Methods. The composition of rocks was determined by the methods of classical silicate analysis, X-ray fluorescence and ICP-MS analysis. Microstructural features, relationships and homogeneity of minerals were studied using an electron microscope LEO-1430 equipped with an energy dispersive spectrometer Inca Energy-300. Isotopic compositions of oxygen were carried out using a mass spectrometer Finigan MAT 253 in the mode of a constant helium flow. Results. Ore mineralization is specified by the presence of Nb-bearing and less REE-bearing minerals. The studied rocks were divided into two groups: albitized granites, and deep albitized granites and albitites. These groups differ in terms of the presence of accessory minerals. The deep albitized granites and albitites belong to alkaline riebeckite-albite granites containing Nb-, Zr-, Y- and REE-bearing minerals. These rocks contain Y-bearing minerals - thalenite and yttrialite, with an up to 4 wt % inclusion of Y 2 O 3 in titanite, chevkinite, thorite and monazite. In contrast, the albitized granites contain fewer amounts of Y and HREE along with LREE-bearing minerals (monazite, allanite, fluocerite, samarskit). Conclusion. The selected groups of rocks have been analyzed in terms of their mineral and geochemical characteristics. The main Nb-bearing mineral in albitized granites is columbite. Minerals from albitites are rich in Y and HREE. The isotopic investigation has shown involvement of a magmatic-derived fluid in the rock formation process.

Research subject. The Novo-Akhmirovskoe lithium-bearing deposit in the East Kazakhstan region, which is represented by an intrusive layer of topaz-zinnwaldite granites, is located within of the Kalba-Narym-Koktogai lithium-tantalum raremetal-granite belt. Being part of the Altai collision system, this belt is considered unique in terms of its length (more than 1000 km). Ores in the Novo-Akhmirovskoe deposit are represented by massive to low porphyry leucocratic granites composed of quartz (30–40%), albite (25–40%), microcline (15–35%), lithium mica varying in composition from zinnwal dite to lepidolite (up to 10%) and topaz (up to 5%). According preliminary estimates, the Novo-Akhmirov deposit is factually a poor lithium deposit with the Li2O content of 0.2–0.4 wt % and the estimated Li2O reserves of 110 thousand tones. Despite the favourable infrastructure and close proximity of this stock to Ust-Kamenogorsk mining and chemical-metallurgical enterprises, its ore-generating potential has not been sufficiently studied.Materials and Methods. In this research, we obtained new data on the geological structure, age, mineral composition and formation conditions of topaz-zinnwaldite granites in the Novo-Akhmirovskoe deposit. In addition, a comparative analysis of these ores with the topaz-biotite granites of the Black Sopka massif (0.6–0.7 wt % Li2O in protolitionite) and spodumene granite porphyries of the Alakha stock (Li2O = 0.9–1.1 wt %) was conducted. Results and Discussion. It is concluded that the development of this unique nonpegmatite lithium-bearing deposit requires deep exploratory drilling, mineralogical and technological research of core samples and reconsideration of economic efficiency parameters.

Research subject. This article presents data on the nature of rock deformations in the Bazhenov suture zone. The data was obtained by 40Ar/39Ar dating of mica samples from schists and blastomylonites, which were collected acrossan area extending approximately for 100 km along the Bazhenov suture. This suture separates the Eastern zone of the Middle Urals dipped under the cover of the West Siberian plate from exposed geologic structures of the Urals.Methods.The character of the deformations was studied by means of direct geological observation. The age of the deformations was determined by mica dating using the 40Ar/39Ar method.Results. The deformations were found to have occurred in several phases. The initial phase, which led to the formation of a band of blastomylonites and rocks showing a varying degree of schistosity with a width of over 10 km in particular areas, is likely to have had the character of left-lateral fault. The upper age limit of this deformation phase is determined by the intrusion of the subalkaline rocks of the Petukhovskii complex (280 Ma), which had not been affected by any deformation processes. The subsequent type of deformations had been left-lateral strike-slip faults of submeridianal strike and subvertical dip, which were represented by low-thickness (usually about 10 cm, rarely up to 0.5 m) zones of intensely deformed rocks cutting the schistosity of the previous phase at an acute angle. The final phase of the deformations is shown to be a sloping fault. The dislocation planes of this type were represented by slickensides and chlorite incrustations. Despite the apparent polychronicity of the deformation processes, which were established within the Bazhenov suture zone by our geological observations, 40Ar/39Ar age dating identified only one event. The average value of five conducted tests was about 251 Ma. Apparently, this age should be associated with the most recent geological processes having occurred at temperatures sufficient to fully overload the K-Ar isotopic system of the studied rocks, such as the deformations caused by strike-slip dislocations.Conclusions. The strike-slip fault dislocations dated in this work occurred approximately 25 Ma after the completion of the tectonic activity in the Serov-Mauk fault zone, which is located to the west of the Bazhenov zone. In addition, the time of these dislocations very nearly coincides with that of the formation of the grabens of meridional strike at the base of the West Siberian plate, which took place about 250 Ma ago. This supports apreviously made conclusionon the similar character of the geological development of the eastern border part of the Urals and the adjoining basement of the West Siberian plate.

Subject. A systematization of Late-Paleozoic magmatic formations of the Magnitogorsk zone of the Southern Urals in the process of an accretion of the Magnitogorsk paleoarc to the margin of the East European continent (EEC) with formation in Famenian and Carboniferous active continent margin of South-Uralian accretionary-collisional belt was given in the work.Materials and methods. A generalization of published and manuscript materials characterizing magmatism and ore-mineralization of Magnitogorsk zone for the Devonian-Carboniferous-Permian time carried out, additional investigations of chemical composition of rocks (XRF, ISP-MS) characterizing process of accretion, subduction and plume activity, microelement distribution in them was made, the composition of rock-forming and accessory minerals (EPMA) was studied.Results. It is found that the South-Uralian accretionary-collisional belt was beginning to form in the late phase of the development of the Magnitogorsk island arc in the process its collision with EEC margin with formation in the Frasnian and Carboniferous of active continental margin. The products of Late-island-arc volcanism are represented by the porphyrite formation and in the eastern frame of the arc - by subalkaline monzonite-shoshonite-latite volcanic-intrusive association with intermediate characteristics between the subductional and interplate formations. Synchronously with them, in the backarc setting, picrite and meymechite volcanics − derivatives of a mantle plume are formed. In process of substitution of tectonic-magmatic regime from island-arc to margin-continental intraplate-type mantle series were forming. During this period, hot asthenospheric diapirs (plumes) were rising to the bottom of new-formed (accreted) margin-continental lithosphere. Along with the magmatic associations of intraplate type and rock series of intermediate geochemical type, this geodynamic situation in the Southern Urals is characterized by a presence of great volumes of mantle-crust granitoids of gabbro-tonalite-granodiorite-granite type, that were formed with a manifold manifestation of anatexis in a time interval of 365-290 Ma.Conclusion.On the whole the originality of Magnitogorsk zone geological history in the Devonian and Carboniferous, peculiarities of magmatic complexes formed here due to various geodynamic settings, are making this zone an extraordinary interesting and important object to study of processes of plume-lithosheric and mantle-crust interaction.

Research subject. In this research, we set out to investigate polyhalite-containing rocks of the Southern Urals. The purpose of this study was to characterize the patterns of formation and transformation of polyhalite-containing rocks, as well as to identify conditions leading to their destruction. Materials and methods. We studied available literature and archive materials on the southern Urals, as well as core samples. Samples for thin sections were taken from the core of polyhalite-containing rocks. The sections were manufactured (where possible) in 2 mutually perpendicular cuts relative to the axis of the monolithic core sample. Considering a high solubility of salt minerals (halite) and the possibility of converting other minerals in aqueous media (e.g., polyhalite into gypsum due to the leaching of K and Mg cations herefrom), thin sections were manufactured in anhydrous liquids (kerosene, transformer oil). In order to determine the mineralogical composition, as well as the structural and textural features of the polyhalite-containing rocks under study, a petrographic analysis of the thin sections was carried out optically using a Polam-213 microscope. Geological sections were built using Corel Draw 13. To this end, geophysical data (gamma-ray logging) and lithological composition were studied.Results. It is found that pelitomorphic sulphate clusters transform into polyhalites followed by their further recrystallization into crystalline accretions. The diagenetic nature of this process is presumed. The location of polyhalite mineralization in the rocks under study confirms the effect of the basin bottom paleorelief on the intensity of polyhalite material accumulation. Conditions determining further destruction of these rocks were formed in local areas under the influence of various geological processes. Conclusion. The results of our research can be used for predicting zones rich in polyhalites in the southern Cis-Urals.

1. Classification is one of the main elements of man’s thinking. Its roots have been laid in the man’s thinking at biological, subconscious level. To overcome the intuitive component of the research of classification problematics reflection (ideas about ideas) is needed. A great amount of studies on different classification questions is widely published. To make this amount visible seems to be useful. 2. A great number of questions connected to classification is supposed to be called “classiology” science. The following parts are suggested to be identified in it. Introduction into the problem. Preliminary positions (prolegomena). Basic notions and preliminary problematics, which are to be adopted or stated before considering the classification problems are included. Classiology(s. s.) is subdivided into two part - general questions and systematic part. In general questions of classiology (s. s.) its basis notions are defined: 1) class system - classification, science about it - the science of classification; 2) procedure of class system construction - classifying, the science about it - systematization; 3) procedure of the referring of the object to one of the system's classes - diagnosis, the science about it - diagnostics; 4) notion, binding notions 1-3 - classiosystem, science about classiosystems - syncretic classiology (synclassiology). According to the variety of classiology activities - general, branch and concrete classiology are suggested to be identified. Systematization classiology (s.s.) consists of structures, defined by the titles of the notions. 3. Geological classiology and biological classiology (biological systematics) are parts of the suggested system of classiology. They are referred to the subdivision “Branch classiology”. These segments are fractally so vast as classiology in general. And they can also be made visible fractally transporting to them the structure of the system of classiology as a whole. GEOLOGICAL CLASSIOLOGY Introductory part Preliminary positions (geoprolegomena) Geological classiology (s.s.) General question of geological classiology Systematic geological classiology General geological classiology Branch geological classiology Concrete geological classiology BIOLOGICAL CLASSIOLOGY (BIOLOGICAL SYSTEMATICS) Introductory part Preliminary positions (bioprolegomena) Biological classiology (s.s.) (Biological systematics) General question of biological systematics Systematic biological classiology General biological classiology Branch biological classiology Concrete biological classiology.

Research subject. In this paper, we set out to investigate main paleostructures in Kazakhstan. In particular, we attempt to clarify or revise their existing geodynamic structures and to show key stages in their development on the basis of new data on the age of some stratigraphic units and rocks of the ophiolitic association. Materials and methods . The work was based on the materials of long-standing geological research performed by the authors, including government-funded geomapping, tectonic zoning and paleoreconstruction, as well as the revision of literature data. Results . It is shown that the main sedimentary, volcanogenic, volcanogenic-sedimentary and intrusive complexes were originated in the western part of the Central Asian fold belt (Paleozoic Kazakhstan) in place of various structures differing in their geodynamic environment and tectonic history throughout the Proterozoic and entire Paleozoic periods. The Epigrenville microcontinent disintegrated into individual massifs has been described, along with rift depressions, basins with oceanic crust, island arcs and island arc systems, the Epicaledonian continent, continental depressions, regional volcano-plutonic belts and marginal basins . The tectonic zonality of Kazakhstan has been presented in the form of diagrams. The mapping of the Precambrian Ulutau massif has been conducted. The distribution of the Devonian complexes and the Late Paleozoic complexes of Kazakhstan is schematically represented. Conclusions . We have refined and partially revised the existing concepts and tectonic consecution on the territory of Kazakhstan. On the basis of paleoreconstructions, key stages in the development of main paleostructures have been established; features of the geological evolution of Kazakhstan paleozoids and their relationship with tectonic processes in the Central Asian fold belt have been determined. It is shown that the modern structure of Kazakhstan paleozoids was evolving over a long period and in many stages for almost 900 million years.

Research subject . In this article, we present the results of comparative mineralogical and geochemical studies of organic remains and coprolites from the Lower Triassic and Paleogene continental deposits of the Northern Urals and East Kazakhstan. Methods . The studies were conducted using a wide range of analytical methods, including optical microscopy; chemical analysis; determination of C org content; thermal and powder X-ray diffraction analysis; spectroscopy; scanning electron microscopy; X-ray fluorescence analysis; isotopic analysis gas pyrochromatography; inductively coupled plasma mass spectrometry. Results . A significant concentration of fish bones, teeth and scales, as well as coprolites of labyrinthodonts were identified in the Lower Triassic and Paleogene continental-marine terrigenous and carbonate-terrigenous sedimentary rocks of the Northern Urals and East Kazakhstan. In terms of mineral composition, the fossils and coprolites are found to be almost completely composed of B-type carbonate apatite. The phase-heterogeneous impurities in the coprolites are represented by calcite, siderite, barite, polycomponent carbonates of the MnCO 3 –FeCO 3 –MgCO 3 –CaCO 3 system and pyrite. It should be noted that pyrite demonstrates octahedral habitus, which is rather rare for this mineral. The ratio of the essential and xenobiotic elemental concentrations differs for the Lower Triassic and Paleogene coprolites, reaching 0.17 and 0.35 on average, respectively. For the first time, information has been given on the content of lithogenic gases in coprolites and the isotopic composition of the impurity carbonaceous material. According to this data, Lower Triassic labyrinthodonts could feed on plants, as well as herbivorous and carnivorous fish. Conclusion . The findings of coprolites in the Northern Urals and East Kazakhstan in a wide Meso-Cenozoic chronological range and in highly different geological settings indicate the probability of a much wider development of coprogenic-phosphate sedimentary rocks in nature than it has been previously considered. Under a high concentration of coprolites, these rocks can serve as a new and extremely valuable type of phosphorite raw materials, the utilization of which would not require any preliminary treatment.

Research subject . This study was aimed at examining iron ore and ore-bearing strata in the Pervy Severny iron ore district in the Northern part of the Tagil depression. This area features several ore occurrences and three small industrial objects, which have been almost completely exhausted, namely the Pervoe Severnoe, Sukhodoyskoye and Peshchernoe deposits. Materials and methods . The research was based on the analysis of published materials and available production reports on the aforementioned objects, as well as the author’s own field observations and search for similar deposits in literature sources. Results . It has thus far been believed that magnetite ores were formed by contact-metasomatic interaction of Givetian limestone and the intrusions of dolerites and gabbrodiorites. However, the area under study is characterized by very few typical skarns. In addition, the ore bodies here are deposited in accordance with sedimentary and volcanic rocks. Iron ore deposits in the Lan-Dill Region in Germany seem to be the closest analogue, which suggests an alternative (volcanogenic-sedimentary) model of the formation of iron ore deposits in the Pervy Severny iron ore district. Conclusion . The use of the volcanogenic-sedimentary model allows search criteria to be specified, thus significantly increasing prospects of detection of new industrial iron ore deposits.

Research subject . High-magnesium rocks associated with the granitoid massifs of the Urals are represented by gabbro-diorites and their melanocratic varieties (hornblendites), as well as by diorites and quartz diorites. These rocks are composed of amphibole porphyrocrists frequently combined with clinopyroxene and phlogopite immersed in a basis of acid plagioclase with interstitial quartz and potassium feldspar. In addition to a high magnesium content of 0.5–0.8 units, these rocks are characterized by extremely high chromium contents of up to 1200 ppm. Methods . The study of the composition of high-magnesium rocks was performed using an ELAN 9000 inductively coupled plasma mass spectrometer, an SX-100 Cameca electron probe microanalyzer and an energy dispersive device INCAEnergy 450 X-Max 80. The detection limit for Cr 2 O 3 was equal to 0.05 wt. % and 0.2 wt. % for the microanalyzer and the energy dispersive device, respectively. Results . The two main mineral associations related to magmatic and post-magmatic processes are found to be different in terms of chromium behaviour. The average concentrations of chromium oxide in the minerals from the magmatic association varied within the range (wt. %) of 0.10–0.50, 0.29–0.68, 0.08-0.36 and 0.0–1.6 for different samples of clinopyroxene, amphibole, phlogopite and their variations, respectively. The post-magnetic association included minerals representing the products of postmagmatic (hydrothermal) transformation of pyroxenes and alumina amphibole into low-alumina magnesia hornblende, actinolite, titanite, epidote and muscovite. The transformation of chromospinelide at this stage had been accompanied by exchange processes with silicates, as a result of which the silicates were enriched with chromium. The average concentrations of chromium oxide in the minerals of this association were (wt. %) 0.24–0.80, 1.38–3.08, 1.03 and 3.5 in the samples of amphibole, epidote, titanite and muscovite, respectively. Conclusion . It is assumed that the crystallization of the early association of iron-magnesium silicates proceeded from aqueous high-magnesium melts. The subsequent post-magmatic change of such silicates led to the development of phases with a similar and occasionally higher chromium content. This fact can be explained by the interaction of silicates with chromite under the conditions of low fluid oxidation, which was insufficient for the formation of magnetite.

Subject.The article is aimed to evaluate of the conodont diversity dynamics at the species level in the Famennian – Serpukhovian interval.Materials and methods.The database compiled from the published and original data contains information on the stratigraphic ranges of 389 Famennian-Serpukhovian conodont species (https://1drv.ms/x/s!AvPFMTPLPc7T4nFU81CaO5UJ6nlw). Conodont zones compose the geochronological basis of the database. The conodont diversity, origination, extinction, and diversification were calculated. Dynamics of these parameters in the Late Devonian–Early Carboniferous was analyzed.Results.The Famennian-Serpukhovian conodonts demonstrate four cycles in the diversity: the early Famennian (triangularis-early postera zones), the late Famennian (late postera-praesulcata zones), the Tournaisian (sulcata-anchoralis zones), and the Visean-Serpukhovian (texanus-bollandensis zones). The cycles are separated by the low-diversity episodes. The highest diversity (80 species) is detected in the early and late marginifera zones (Famennian).Conclusions.The successive decreasing in diversity comprises interval from the late Famennian through Serpukhovian. The global events gave little influence on the conodont diversity except for the Frasnian/Famennian (about 70% conodont species became extinct) and Devonian/Carboniferous extinction events. Conodont diversity demonstrates weak dependence form the global sea level fluctuations. The transition from the green-house to ice-house climate at the beginning of the Carboniferous and successive changes in the marine ecosystems are considered as main probable cause of the decline in conodont diversity in the late Tournaisian-Serpukhovian.

Research subject. The deep structure of the Yugan-Koltogor zone located in West Siberia was investigated with the purpose of detecting prospective oil and gas bearing areas.Materials and methods. The methods of lineament extraction and the computer modelling of rock density were employed. Lineament extraction was conducted on the basis of geophysical data, including detailed (1 : 200 000) maps of anomalous magnetic and gravity fields. In order to detect faults, telemetering methods were used, along with the results of studies conducted to investigate core materials from wells in the region. The modelling of the deep structure of the pre-Jurassic basement was performed on the basis of its geological map by solving a direct problem while fitting geological body densities.Results. Six largest faults of the Yugan-Koltogor zone identified on the geological map by a special sign “deep faults and regional schistosity zones” are of particular interest as possible oil bearing areas.Conclusions. The modelling of the deep structure of the pre-Jurassic basement of the West Siberian Platform has shown the granite decompaction areas of the Yugan zone to be highly promising in terms of oil and gas deposits.

Subject. The article presents the results of study of Mechnikovskoe gold deposit associated with listvenites and beresites of the Miass region of the Southern Urals.Materials and methods. Materials were sampled during the field work of 2010– 2012. The chemical composition of rocks is analyzed by methods of classical chemistry (rock-forming oxides) and ICP MS (trace elements). The mineral composition is determined on an electron microscope with EDS.Results. The deposit is composed of tectonic sheets of serpentinites, carbonatized serpentinites and listvenites (sheet I), metadiabases and plagioclase metabasalts of the Irendyk Formation and beresites and volcanosedimentary rocks and metabasalts of the Karamalytash Formation (sheet II). In the central part of the deposit, the volcanic rocks are intruded by a dike of finegrained island-arc granites. Chromites of serpentinites are characterized (on average) by high Cr# (89) and low Mg# (29) values and low contents of Al2O3 (6.94 wt %) and MgO (5.5 wt %). Gold-bearing rocks include listvenites, beresites and carbonaceous shales. The major ore mineral is pyrite; accessory minerals are Au and Ag minerals, chalcopyrite, fahlores, galena, sphalerite, pyrrhotite, cubanite, vaesite, melonite, secondary copper sulfides, barite, rutile, monazite and xenotime. Gold of the deposit contains low Ag contents (3.52 wt %) and minor amount of Cu and Hg (Conclusions. The listvenites and beresites of the deposit were formed after ultramafic and mafic rocks, respectively. The discovery of gold in various rocks indicates that gold mineralization was deposited after the formation of the geological structure of the deposit. The source of gold was most likely related to a magmatic fluid.

Оbject.The article presents the results of studies of secondary mineral formation in the lower Cretaceous sediments of the Bolshekhetskaya depression, which contain highly promising oil and gas deposits, with established industrial performance at Pyakyakhinskoye, Khalmerpayutinskoye and South-Messoyakhskoye fields. The objects under consideration are located in the most submerged part of the Nadym-Taz syneclise in the zone, where the Taz and Urengoy facies regions meet.Materials and methods.Main types of postsedimentary changes of reservoir rocks selected on the basis of study of core material Pokurskaya, Angelovskaya, Sortymskaya and Megionskaya fms. Petrography and Mineralogy of the rocks under consideration were studied on the basis of stage analysis using optical and electron microscopy, and X-ray diffraction study at the Center of core and reservoir fluids research of “LUKOIL-Engineering’s KogalymNIPIneft branch In Tyumen” (Kogalym). Determination of the mineral type of zeolite was performed by X-ray phase analysis at the Institute of Geology and Geochemistry UrO RAS (Ekaterinburg).Resuts.It was found that for rocks Pokurskaya, Angelovskaya, Sortymskaya and Megionskaya fms characteristic a diverse range of secondary minerals and structures, evidence of the background stage catagenesis and the superimposed processes. The most important among them is the regeneration of quartz, the transformation of feldspar, violation of the crystal structure of biotite, the formation of various clay minerals, crystallization of zeolites and calcite.Conclusions.Studies show that the upper part of the section of the lower Cretaceous deposits of Bolshekhetskaya depression corresponds to the area of the middle catagenesis (gradation MK2), the bottom – changed to the stage of deep catagenesis (gradation MK3). In this case, the epigenetic process proceeded unevenly, pulsation, due to changing tectonic conditions. Particular attention is paid to the origin of zeolites, which is still debatable. It is assumed that their formation is associated with the transformation of “camouflage pyroclastic” in particular, feldspar clastics.

Research subject.The West Magnitogorsk zone of the Southern Urals in the vicinity of the Ishkildino village features a subaerially exposed basaltic sequence superposed by cherts and siliceous-clay shales. The basalts and the overlying shales are assumed to have formed during the Ordovician and Silurian (?)–Early Devonian (up to the conodont zone excavates inclusive) periods, respectively. The aim of this research was to reconstruct, using geochemical data, the conditions under which the rocks present in this geological location were formed.Materials and methods. Five samples of the basalts (XRD and ICP-MS methods), 27 samples of the siliceous-clay shales and 10 samples of the cherts (XRD and ICP-AES methods) were analyzed.Results.According to the ratio of SiO2, Na2O and K2O, the volcanic rocks from the lower part of the section are represented by basalts and trachybasalts. Their geochemical composition corresponds to the N-MORB and is established to be similar to that of the basalts in the Polyakovskaya formation (the Middle–Upper Ordovician). In terms of main elements, the shales under study consist of quartz and illite with a slight admixture of organic matter, goethite, quartzfeldspar fragments, etc. The degree of the sedimentary material weathering according to the CIA, CIW and ICV index values is shown to be moderate. The values of Strakhov’s and Boström’s moduli correspond to sediments without the admixture of underwater hydrothermal vent products. The values of Cr/Al, V/Al and Zr/Al correspond to those characteristic of deposits in deep-water zones remote from the coasts of passive and active continental margins, basalt islands and areas adjacent to mid-ocean ridges. For most samples, the values of Ni/Co, V/Cr, Mo/Mn are typical of deposits formed under oxidative conditions. However, several samples from the upper part of the section, which is comparable to the kitabicus and excavatus conodont zones, demonstrate the Ni/Co, V/Cr, and Mo/Mn values corresponding to deposits formed under reducing atmospheres. An assumption is made that the existence of these deposits can be associated with the Bazal Zlichov event.Conclusion.The investigated pre-Emsian shales have shown no signs of volcanic activity in the adjacent areas. The studied deposits are established to correspond to the central part of the Ural Paleoocean.

Object of study. The article presents of the petrographic study results of the garnet-containing rocks from the Ufaleiskii complex, located on the border of the Ufaleyskii metamorphic gneiss-amphibolite block with the Main Ural Fault (GUR). Methods. Petrographic studies were conducted using a polarizing microscope Axiolab ZS и Olimpus BX 51. Chemical composition of garnets is performed on the raster electron microscope of the РЭММА-202М with an energy dispersive spectrometer LZ-5. Results. Investigations made it possible to distinguish two types of garnet-containing rocks. One type, in which garnet was formed after amphibole (amphibolites and gornbendites), and the second one, in which garnet is the primary mineral (metamorphic schists). Zoisite and chlorite are formed in rocks of the first type together with granate. CaO, MgO, FeO and Al2O3 were extracted from amphibole, in the process of crystallization of garnet, some of these components went to form zoisite and chlorite, and the released silica formed quartz. Garnet grains in these rocks are 64–68% composed of almandine. In the rocks of the second type, represented by biotite-hornblende, biotite-chlorite-quartz and double-mica schists, garnet is the primary mineral formed from the original rocks in the process of progressive metamorphism. The composition of the garnet in these rocks correlates with the composition of the original rock. Conclusion. A complex of garnet-containing rocks with a high content of granulated quartz may be of interest as a raw material for obtaining pure quartz concentrates. The paper presents the results of a detailed petrographic study of all types of rocks of the complex and discusses possible options for their genesis.