Research subject. Hypabyssal intrusive bodies of a gabbro-dolerite-monzonite-granodiorite composition, common among the Devonian island-arc sequences of the East Tagil structural-formational zone in the Northern Urals. These bodies are dated as the Late Devonian-Early Carboniferous and attributed to the post-accretionary continuously differentiated Ivdel complex. Material and methods. The composition of rock-forming and accessory minerals of these intrusive bodies was studied using an SX-100 microanalyzer. This made it possible to obtain new data on the conditions of their formation, features of the fluid regime, and potential ore content. In addition, the geodynamic setting of this period was clarified, along with the composition, possible position of the primary mantle source, and the features of its fluid regime. Results. It was established that the mafic rocks (dolerites) in the Ivdel complex correspond to derivatives of the depleted mantle, with a primary source close to N-MORB basalts. The connection between the source and the separation of the slab and the “mantle window” located under the frontal zone of the former East Tagil island arc was substantiated. Such a position of the melting chamber determines the primary weak water saturation of dolerite magmas and their redox regime. According to mineralogical data, this feature is further manifested in the formation of the entire series of rocks of the Ivdel complex (with an increase in the iron index of clinopyroxenes and amphiboles, an increase in titanium contents in titanomagnetite, and other data). Further evolution of magmas (from dolerites to monzonites, quartz diorites, and granodiorites) occurred as they moved upward to the Earth’s surface and reflected the increasing contamination of differentiated melts by suprasubduction island-arc matter. Another important petrological feature of this complex is its formation with the participation of a chlorine-rich magmatogenic fluid. Depending on the composition of intruding melts, their contents of water, chlorine and oxygen activity, a number of autonomous degassing fluid-magmatic systems are formed. These systems are characterized by noticeable features in the processes of post-magmatic autometasomatosis, with the participation of an iron-chloride fluid. According to the regime of volatiles (halogens, water, and oxygen), the common affiliation of such autonomous fluid-magmatic systems to titanomagnetite ferrofacies (according to G.B. Fershtater), determines both their general metallogenic specialization and potential ore content. The removal of volatiles from such fluid-magmatic systems could be accompanied by extraction and transfer of chlorophyll ore elements from crystallizing melts to exocontacts of intrusive bodies. This, in the presence of migration zones favorable for fluids (faults, crushing zones, etc.) and geochemical barriers (especially in the presence of favorable enclosing sulfide-bearing island-arc strata), could have contributed to the formation of hydrothermal-metasomatic ore mineralization (Cu, Zn, Au, Mo and etc.). Such ore-bearing zones during erosion could be the primary source of gold for the known placers of this region. Large bodies of gabbrodolerites of the Ivdel complex may be promising for high-Ti magnetite-ilmenite mineralization.

Research subject. Clay rocks of the Lower, Middle, and Upper Riphean (respectively, the Burzyan, Yurmatau, and Karatau groups) of the Western slope of the Southern Urals. Changes in their characteristic values of a number of ratios of oxides and some trace elements that are indicators of rock composition in provenances are considered, taking into account the breaks of different duration present in the Riphean stratotype. Methods. Calculation of t he average values of TiO2/Al2O3, Th/Sc, La/Co and (La/Yb)N, typical for shales, fine-grained clay siltstones, and mudstones of the main lithostratigraphic units of the Riphean stratotype (formation and, in some cases, subformation) and analysis of their changes taking into account the hiatuses known in the Riphean stratotype (Pre-Mashak/Pre-Zigalga, Pre- Zilmerdak, Pre-Minyar, Pred-Uk). Results. It was established that throughout the entire Riphean, regardless of breaks in sedimentation, presumably associated with certain transformations in the areas of erosion and sedimentation, a number of lithogeochemical characteristics of fine-grained clastic rocks of the Burzyan, Yurmatau, and Karatau groups (such as TiO2/Al2O3, Th/Sc, La/Co, and, to a significant extent, (La/Yb)N) practically did not experience significant changes. Conclusions. The data obtained give reason to think that there were no fundamental changes in the composition of the sources of fine-grained aluminosiliciclastics for the Riphean sedimentary sequences for more than 1 Ga, and contradict the rather active scenario of tectonic processes at the end of the Early Precambrian and the entire Late Precambrian. Conversely, the data on the values of tNd(DM) and eNd(t) in 37 samples of clay rocks of the Riphean stratotype nevertheless reflect a change in the composition of the rocks of the feeding provinces and, one way or another, fit into the outline of subglobal events established by conventional geological methods in the stratotype area of the Riphean. In accordance with them, in the Ai and Mashak times, an increase in the proportion of juvenile material took place in the areas of erosion. Apparently, the Pre-Zilmerdak hiatus also led to the appearance of a significant proportion of basic igneous rocks among the rocks of the provenances.

Research subject. Upper Batian deposits (formation U2) of the Eastern part of the Kogalym region, within the North Nizhnevartovsk monocline. Aim. Reconstruction of the sedimentation environment of the U2 formation in the Kogalym region. Materials and methods. The reconstruction of sedimentation environments was conducted based on a macroscopic description of core samples with identification of structural and textural features of rocks from 35 wells. The clarification of sedimentation settings was carried out based on the description of 41 thin sections and a granulometric analysis of the clastic part of the studied rocks. Results. According to the macroscopic study, the U2 layer is composed of an uneven alternation of silty-argillaceous and silty-sandy rocks with coal interlayers. The rocks are of a polyfacial nature, represented by deposits of continental, transitional, and marine genesis. The thickness of the deposits varies markedly depending on the paleorelief of the area. The optical petrographic study revealed the polymictic composition of the studied rocks, which, according to the classification by V.D. Shutova, correspond to the arkose (graywacke arkose), less often graywacke (feldspar-quartz, quartz-feldspar greywackes) group. Cement most often exhibits a carbonate-clay composition. Rocks of marine genesis are characterized by a decrease in the proportion of rock fragments and an increase in the proportion of mechanically stable accessory minerals (zircon, garnet, tourmaline). The rocks of continental genesis are characterized by the maximum content of micas and plant detritus. An increase in the content of pyrite is noted in the sediments transitional from the continent to the sea. The grain-size analysis data of reservoir rocks of the U2 formation showed that both coastal-marine and channel deposits were formed in environments with active hydrodynamics of the medium, when the dynamic processing of clastic material exceeded the intensity of its supply. Conclusions. The performed lithofacies studies made it possible to reconstruct the sedimentation environment, as well as to reveal specific features in the distribution of the silty-sandy rock components of the U2 formation.

Research subject. Yanovstan f ormation ( J3-K1jnv) of Kimmeridgian-Early Beriasian age. Aim. To identify structural features of the Yanovstan formation, to carry out a detailed correlation of its deposits, including the development of criteria for determining the boundaries of the suite. Materials and methods. The studies were carried out on the basis of borehole data, including core material from 5 boreholes and borehole logging data from 209 boreholes. The borehole logging complex comprised the following methods: gamma ray logging, neutron gamma ray logging, acoustic logging, caliper logging, as well as apparent resistivity and self-polarization logging. The borehole sections were correlated by tracing individual sections of the geological section, which are characterized by relatively stable geophysical parameters. Additionally, a sequence stratigraphic approach was used. Results. The boundaries between the Sigov and Yanovstan formations were identified based on the description of core material and its comparison with the borehole logging data. The Yanovstan formation was subdivided into three units proposed by the authors: lower (ЯНв), middle (ЯНб), and upper (ЯНa). A borehole correlation of the units of the formation was carried out, on the basis of which maps of the total thickness and net-to-gross ratio and the structural plan of each of the identified stratigraphic units were constructed. It was determined that the total thickness of the lower unit reaches 80 m and is characterized by maxima within the eastern part of the study area. The thickness of the upper unit reaches 240 m and is identified within the northeastern part of the area. This part is represented by a predominantly clay composition. The total thickness of the formation as a whole varies from 40 m in the west to 320 m in the northeast. The thicknesses of the middle unit are relatively consistent throughout the study area. The sandiness of the lower unit varies from 0 to 0.27 units; the upper ranges within 0–0.45 units. The middle unit is not characterized by the presence of sandstones. Conclusions. The theory about the supply of sedimentary material during the sedimentation of the suite from paleomounts within the eastern edge of the West Siberian Jurassic paleobasin was confirmed. An assumption was made that the increased thickness of the predominantly clayey suite within the northeastern part of the study area is associated with the redistribution and transfer of terrigenous material carried from the Siberian land by currents moving unidirectionally along the coast (counterclockwise). These currents thus seized the lightest (clayey) material and transported it to the northern part of the basin.

Research subject. The paper presents the results of a study into the carbonate-terrigenous section of 197.8 m-thick Wenlockian section in the Shchugor River basin, which is proposed as the stratotype of the regional horizon. Materials and methods. The study was based on numerous samples from Lower Silurian deposits collected by the authors in different years during fieldwork on the Western slope of the Circumpolar Urals and the Chernov and Chernyshev uplifts, as well as the biostratigraphic, paleontological, lithological, and C-isotopic data obtained during these works. Results. The obtained data allowed revising some of the established ideas about the structure of the Lower Silurian section and the position of the boundary level between the Llandoverian and Wenlockian in the Subpolar Urals and to identify a new regional subdivision with the name “Voyvyv”. The traced formation conditions of shallow carbonate sediments of the Voyvyv horizon and the consistent change of zonal taxa of marine fauna in the stratotype section indicate similarity with coeval strata on the Chernov and Chernyshev uplifts and Dolgy Island. Conclusions. The results of the study of Wenlockian Voyvyv deposits in the Timan-North Urals region showed that the section in the Shchugor River basin in outcrop 10c can be considered the most informative in the Northern Urals region in terms of exposure degree, established stratigraphic completeness, and preservation of macro- and microfauna.

Research subject. Section of boundary deposits, exposed in the right side of the Zakola stream (the right tributary of the Ilych River, Northern Urals) with a total thickness of 98 m, presented with rock samples (more than 100 pieces), thin sections (100 pieces), slabs (10 pieces), and chemical analyses (15 pieces). Aim. Detailed description of the most complete section of the Upper Ordovician–Lower Silurian boundary sediments of the Shantym facies complex with a stratigraphic reference of layers, lithological typification of sediments, and restoration of sedimentation conditions. Methods. Conventional lithological and paleontological methods were used to dissect the section. Sampling was carried out after 1 m; however, samples were additionally taken when detailed observations were possible to identify lithological and facial differences. The thin sections were studied by the classic method of optical microscopy. The study of the fauna complex was carried out both by collecting samples of the author’s rocks and by the materials of A.I. Antoshkina. In addition, stock materials were attracted. Results. In the section, 14 packs of rocks were identified, which are represented by 6 lithological types of secondary dolomites. Their distribution along the section, along with the presence of characteristic faunal remains, made it possible to establish three members in the section, which can be correlated with the Katian, Hirnantian, and Ruddanian stages of the General Stratigraphic Scale. Conclusion. The Katian deposits are represented by the Yaptikshor Formation (Strata 1), which was formed under the conditions of the lower sublittoral of a ramp-type carbonate platform with a transgressive carbonate tract and a diverse fauna. The beginning of the Hirnantian (Strata 2) is characterized by shallow water conditions of the upper sublittoral up to the littoral, which reflects a sharp shallowing at the Katian–Hirnantian boundary and corresponds to the beginning of the global early Hirnantian regression. The rocks exposed higher up the section indicate sedimentation with a certain rise in the sea level; however, the correlation of this part of the section with the upper part of the Verkh Ruchey Formation is complicated by the fragmentary nature of the outcrops. The overlying Ruddanian deposits (Strata 3) were accumulated on the outskirts of a ramp-type carbonate platform under the conditions of the lower sublittoral, which corresponds to the beginning of the Early Silurian global transgression.

Research subject. The gold-bearing potential of modern (oceanic) and ancient industrial types of phosphorite ores, including aphanitic, microgranular, granular, nodular, shell and karst. Aim. To assess the ability of phosphorites to accumulate gold to industrial concentrations. This issue has been actively discussed in the geological community in recent years due to the advent of high-precision methods for studying matter. Methods. Russian and foreign publications, unpublished geological data, as well as the authors’ data collected over a 30-year period of studying phosphorites. Results and discussion. In the section, 14 packs of rocks were identified, which are represented by 6 lithological types of secondary dolomites. Their distribution along the section, along with the presence of characteristic faunal remains, made it possible to establish three members in the section, which can be correlated with the Katian, Hirnantian, and Ruddanian stages of the General Stratigraphic Scale. Conclusion. Conditions for the possible joint accumulation of phosphates and gold are manifested in black shale basins, as well as in shelf shallow waters with glauconite-sand sediments. However, due to significant differences in the natural features of gold and phosphates, their industrial clusters are formed separately from each other. This is evidenced by the insignificant accumulation of phosphorus in the ores of gold deposits of black shale formations,as well as its low-quality concentrations in industrial phosphorite beds of phosphorite-bearing basins. For gold, phosphorites are only temporary collectors, the productivity of which depends on the combination of many, frequently random and slightly related factors.

Research subject. The composition, properties, and connection of the lattice defects in the disordered s tructure of quartz with the conditions of its formation. Materials and methods. The quartz of the gold deposits of the Darasun ore field – Darasun, Teremkinskoye, and Talatuy – were studied. For the purpose of comparative analysis, gold-ore quartz from the deposits of Northern Kazakhstan was used. Registration of centers in quartz samples was carried out by the EPR method. When interpreting the obtained results, genetic information consisting in the distribution of substitutional Ge and Ti impurities in quartz was used. Results. Two groups of paramagnetic centers were identified in the quartz under study. One of them is associated with substitutional Al, Ti, and Ge impurities in quartz zones with an ordered crystal structure, while the other is associated with the lattice defects localized in the disordered crystal structure of quartz. The latter group includes several types of E'-centers formed in quartz glass and Al-X-centers caused by Al3+ ions associated with oxygen vacancies. In the case of stable thermodynamic conditions of mineral formation, a linear relationship was established between the concentrations of Al-X-centers (CAl-X) and E'-centers (CEs). Under a change in thermodynamic conditions, a deviation of the points from the CEs(CAl-X) dependence was observed. Conclusions. The type of CEs(CAl-X) dependence is determined by the thermodynamic conditions of mineral formation and can be used to identify cases of non-equilibrium solidification of quartz.

Research subject. Platinum–metal objects of the Kola region (contact type mineralization), including the Yuzhnosopchinskoye ore occurrence within the same-name massif belonging to the Early Proterozoic Monchetundra intrusion and the Fedorova Tundra deposit located in the western part of the Early Proterozoic Fedorovo-Pansky layered complex. Aim. To establish the formation conditions of platinum-metal ores in the Yuzhnosopchinskoye ore occurrence and the Fedorova Tundra deposit. Methods. Comparison of the geological structure and petro-geochemical features of rocks and ores from the two objects using statistical analysis. Results. Both the Yuzhnosopchinskoye ore occurrence and the Fedorova Tundra deposit belong to the contact type of platinum group element deposits. The main characteristic feature is confinement of the ore zone to the contact of two magmatic phases. In the contact zone, igneous breccia, pegmatoid, and vein bodies are widespread, with the latter being especially common in the Yuzhnosopchinskoye ore occurrence. In Yuzhnosopchinskoye ore occurrence, breccia fragments are represented by orthopyroxenites and melanocratic norites of the early magmatic phase (layered series of rocks). They were cemented by barren gabbroids of the later magmatic phase. In the Fedorova Tundra deposit, breccia zone fragments are also composed of orthopyroxenites and melanocratic norites of the early magmatic phase (layered series of rocks). They were cemented by taxitic ore-bearing gabbronorites of the late magmatic phase. Rocks of the two objects with a similar nomenclature demonstrate slight systematic differences in the composition of petrogenic components, as well as in REE and rare elements. Taxitic gabbronorites (rocks of the marginal series) from the Fedorova Tundra deposit have no rock analogues in Yuzhnosopchinskoye ore occurrence. A comparison of similar amounts of two data sets (more than 2000 samples each) of Pt, Pd, Au, Ni, and Cu sampling showed that the content of all precious metals in the Fedorova Tundra deposit was consistently higher than that in the Yuzhnosopchinskoye ore occurrence. The Fedorova Tundra deposit is homogeneous, with an average Pd/Pt ratio of 4.5. The Yuzhnosopchinskoye ore occurrence is heterogeneous and, on average, slightly more ‘platinum’ and less ‘palladium’ than the Fedorova Tundra deposit. Conclusions. The two ore objects of the contact type are similar in many respects, mainly differing in the conditions of mineralization formation. The Yuzhnosopchinskoye ore occurrence entered the contact zone from the rocks of the layered series due to the activation of the ore matter during intrusion of the late gabbroid intrusive phase. The Fedorova Tundra deposit entered the contact zone together with the late ore-bearing gabbronorite magmatic phase.

Research subject. Bottom sediments of Lake Bannoe (Southern Urals). Aim. Identification of lithologic features of Lake Bannoe sediments, which could reflect sedimentation conditions in the Holocene. Materials and methods. The detailed complex analysis included radiocarbon dating, grain-size analysis, X-ray diffraction analysis, electron microscopy, X-ray fluorescence and isotope analysis, coercive spectrometry and pollen analysis. Results. Radiocarbon dating showed that sedimentation in Lake Bannoe began no later than ~13 thousand years ago. Combination of data from various laboratory studies unraveled four lithological zones and the corresponding stages in the sedimentation history. The grain size, allothigenic particles, carbonate minerals, organic matter and isotopic composition of carbon and oxygen are the most informative indicators. Grain size variations and the ratio between allothigenic and carbonate components reflect changes in the Lake’s depth and clastic material supply, which, in turn, is associated with humidity. Organic matter parameters (TOC, δ13Corg, C/N ratio) can be considered as indicators of climate-sensitive changes in bioproductivity of the sedimentation basin. They also reflect the ratio of exogenous and endogenous organic matter in the sedimentary environment. The isotopic composition of carbon and oxygen (δ13Ccarb, δ18Ocarb) in sedimentary carbonates is an informative indicator of lithological zones and climatic events of the Holocene due to its sensitivity to changes in biomass, temperature fluctuations, and fresh water inflow. The paramagnetic component k_para was used as an indicator of the allothigenic material input into the lake basin for the first time in this region. Conclusions. The granulometric, mineral, and chemical composition, as well as the magnetic properties of Lake Bannoe sediments reflect the history of Lake sedimentation in the Southern Urals, which agrees mainly with the climate stages of the Holocene.