Research subject. The research objects included a book section on the Vendian stratigraphy of the Yazvinsko-Kosva sub-zone of the Kvarkush-Kamenogorsk meganticlinorium, written for the Explanatory note to sheet O-40 – Perm of the State Geological Map 1000/3 of the Russian Federation, as well as the results obtained in the course of various thematic (stratigraphic, paleontological, litho- and isotope-geochemical, etc.) studies of the Vendian sedimentary sequences of the indicated territory.

Materials and methods. The materials were facts, ideas and arguments in favor of certain conclusions and ideas of various authors. were analyzed. The methods included the comparison and analysis of facts, conclusions and ideas of predecessors.

Results. It is suggested that the ideas about the architecture of the Vendian deposits of the western slope of the Middle Urals, dating back to the pioneering works of B.D. Ablizin and his colleagues, had almost reached perfection. At the same tim, the attribution of different formations to the regional stages of the Vendian of the East European Platform is still interpreted differently. Studies into the Vendian macrofauna on the western slope of the Middle Urals have also made significant progress in the first two decades of the 21st century, which, however, cannot be said about the studies of microfauna. The dating of detrital zircons from tillite-like conglomerates and sandstones of the Serebryanka and Sylvitsa groups should undoubtedly be continued. For the Vendian of the western slope of the Middle Urals, the dating of zircons from volcanic tuffs/ashes, as well as the search for correlations of already dated various igneous bodies with sedimentary sequences, is still relevant. This search is complicated by mountain taiga conditions. The prospects for studying the chemical composition of heavy fraction minerals, and reconstructing the composition and evolution of clastic sources for sedimentary sequences of the Serebryanka and Sylvitsa groups, seem almost boundless.

Conclusions. The conducted analysis of works published in the first years of the 21st century on various aspects of the geo logy of the Vendian sedimentary sequences of the Middle Urals made it possible to identify their strengths and weaknesses and to outline directions for further research.

Research subject. The anomalous magnetic field of the southern part of the Barents Sea Shelf.

Materials and methods. The research was based on a digital matrix (grid) of the anomalous magnetic field (AMP) compiled from the materials of magnetic surveys performed in 2002–2007 by a number of research organizations and research and production companies. A model describing the structure and formation of the magneto-active layer of the southern part of the Barentsevomorsk region was developed. An analysis of the radially averaged field spectrum made it possible to establish the confinement of the upper edges of the field sources to several structural horizons. Band filtering in the frequency domain in accordance with the allocated depth ranges allowed anomalies to be distinguished from other sources. To determine the nature of sources of magnetic anomalies at different levels of the earth’s crust, an integrated analysis of gravimagnetic fields, seismic profiling data and ground studies was conducted.

Results. At least two levels of magnetic anomaly sources were found: the distribution of effective magnetization for the low-frequency component of AMP, reflecting the depth structure of the region, and the high-frequency component of AMP, reflecting the distribution of local intrusions in the upper part of the foundation and in the sedimentary cover. The lower level is represented by massive blocks of deep laying and corresponds to the SDR (Seaward Dipping Reflectors) complex, which is an alternation of tectonic plates of continental material with ultrabasite basites that were introduced into the crust at the post-rift stage of the continent’s split. The zone of positive linear anomalies of the magnetic field reflects the divergent boundary of the ancient continental plate of the Baltic, which arose during the fragmentation of the supercontinent of Colombia (Paleopangea) in the middle reef and the formation of the Rifean oceanic basin, which was then veiled by subsequent tectonic processes. The upper structural level indicates the introduction of the main composition into the upper layers of the earth’s crust in the zones of rift-forming faults of magma in late Devonian times during the process of continental rifting on the Svalbard Plate. This is confirmed by the presence of manifestations of the main magmatism within the propagation zone of the South Barents riftogenic depression into the body of the Baltic Shield.

Conclusions. The conducted integrated analysis of the anomalous magnetic field and other geological and geophysical data allowed the authors to establish the nature of the sources of magnetic anomalies located at different structural levels of the earth’s crust in the southwestern part of the Barents Sea shelf. The magnetoactive layer of this region is characterized by a complex structure, the section of which includes at least two structural levels, each reflecting certain evolutionary stages of the earth’s crust.

Research subject. The article presents the results of studying traces of the global Late Aeronian biotic and isotopic (δ¹³C_carb) events preserved in a new reference section of the Lower Silurian in the Subpolar Urals.

Materials and methods. The samples of sedimentary rocks and microfauna, the results of isotope analysis, as well as the collections with remains of benthic fauna collected by the authors in different years during fieldwork were investigated. The studies were confirmed by sedimentological, biostratigraphic and chemostratigraphic data obtained by the authors.

Results. The The event-stratigraphic interval, established in the upper part of the Lolashor stage (Aeronian) of the Silurian, is characterized by increasing regressive tendencies, decreasing biodiversity, disappearance of Pranognathus tenuis conodonts and brachiopods of the genus Pentamerus, as well as by δ¹³C_carb anomalies in the upper strata of the Lolashor stage.

Conclusions. The obtained data indicate a eustatic drop in the sea level, a major ecosystem restructuring, and a sedimentation gap at the end of the Lolashor time. The boundary between the Lolashor and Philippel stages (Aeronian and Telychian) records a sharp negative isotopic shift of δ¹³C_carb, which was first observed in the Lower Silurian section in the European Northeast of Russia.

Research subject. The pegmatites of Murzinka-Adui region (Ethtern sector of the Middle Urals), represented by three types of veins miarolitic pegmatites with topaz and beryl (mines Mokrusha, Kazennitsa, Semenovskaia), miarolitic rubillite-lepidolite pegmatites (Lipovka veins field) and rare metal pegmatites with Ta-Nb-Be mineralization (deposits Kvartal’noe and Lipovyi Log).

Materials and methods. Isotope dating was carried out via the ⁴⁰Ar-³⁹Ar method by a mass spectrometer Micromass 5400 at the Institute of Geology and Mineralogy SB RAS for mica of different composition (muscovites, biotites and lepidolites).

Results. ⁴⁰Ar/³⁹Ar ages for mica from dated pegmatite veins of the topaz-beryl type coincide within the measurement accuracy: mine Kazennitsa – 252.3 Ma, Mokrusha – 253.7 and Semenovskaia – 250.3 Ma. The average age of the two series of mica from rubillite-lepidolite pegmatites was found to be 254.1 Ma. The average age of four samples of muscovites from rare metal Ta-Nb-Be pegmatites equals 252.6 Ma.

Conclusions. The closure of the isotope system of micas in pegmatites of all three studied types (topaz-beryllium, rubillite-lepidolite and rare-metal with Ta-Nb-Be mineralization) occurred almost simultaneously during the timeframe of 254 to 250 Ma years ago. The obtained age values, however, cannot be identified with the time of formation of pegmatites. The analysis of the available data suggests that the closure of the micas K-Ar isotope system of the studied pegmatites as well as previously dated schists and blastomylonites of the Bazhenovo suture zone and granites of the Murzinka-Adui block marks an important episode in the geological history of the eastern margin of the Urals and the basement of the adjacent part of the West Siberian plate: the change of the transpression regime prevailing during the collision stage of the region’s development to the regime of limited postcollision extension.

Research subject. Permian-Triassic flood basalts in the basement of the Arctic zone of the West Siberian Platform locate mainly in graben-rift structures. Flood basalts in this region remain to be understudied in comparison with other areas of its distribution, mainly due to the significant depth of their occurrence (4–6 km).

Materials and methods. 36 core samples from 11 superdeep and deep boreholes were studied. Isotopic ratios were measured on mass spectrometers NEPTUNE PLUS (Nd, Sm) and TRITON PLUS (Rb, Sr). Bitumen were studied using a Raman spectrometer LabRAM HR800 Evolution. The Raman spectra were deconvoluted (“Peak fitting” procedure), and the bitumen conversion temperature was estimated.

Results. About half of the samples of volcanic rocks underwent metamorphism of the prehnite-pumpellite and locally greenschist facies or intense low-temperature hydrothermal alteration. The studied basalts are close to typical flood basalts and are somewhat similar to island-arc volcanic rocks in terms of their geochemical characteristics. For the first time, thin inclusions of bitumen were found in the amygdalae of Permian-Triassic basalts in the superdeep borehole Tyumenskaya SG-6 at a depth of 7310.6 m. A high similarity of the studied volcanics by geochemical characteristics and the isotopic composition of Sr and Nd with the flood basalts of the Siberian platform is shown.

Conclusions. The presence of a negative Ta, Nb, Ti anomaly, as well as a negative Ce anomaly, in some of the analyzed samples indicates a possible contamination of the basalts by island arc volcanics and volcanogenic-sedimentary rocks. The temperature of transformation of bitumen in inclusions in basalts from the well Tyumenskaya SG-6 according to Raman spectroscopy is estimated at 150–300°C and generally corresponds to the temperature of metamorphism of the host basalts. The presence of bitumen in the amygdalae may indicate the migration of hydrocarbons through the basalts.

Research subject. Au-Pd mineralization of the Bleïda Far West deposit, represented by an unusual association of palladium gold, minerals of the Pd-Bi-Se system, as well as silvery gold and minerals of the Pd-Bi-Te system. The deposit is localized in the Neoproterozoic volcanic rocks of the central Anti-Atlas (Morocco).

Methods. A chemical analysis of minerals was carried out at the Center for Collective Use of Multielement and Isotopic Studies of the Siberian Branch of the Russian Academy of Sciences (Novosibirsk, Russia) using the electron probe microanalysis (EPMA) method. Fluid inclusions were studied using cryometry and homogenization using a THMSG-600 microthermochamber. The composition of the gas phase and the determination of the solid phases of the inclusions were carried out by Raman spectroscopy. The qualitative chemical composition of fluid inclusion salts was determined by the EPMA method.

Results and conclusions. It is suggested that palladium gold and minerals of the Pd-Bi-Se system were formed under the conditions close to those during the formation of Au-Pd infiltration deposits in Brazil, while silvery gold and minerals of the Pd-Bi-Te system could be formed under the conditions similar, but not identical, to the formation conditions of Au-Pd low-temperature mineralization in porphyry deposits. According to the study of fluid inclusions in quartz and calcite, Au-Pd mineralization was formed at temperatures from 384 to 75°C with the participation of homogeneous or heterophasic CaCl₂-NaCl highly saline hydrothermal solutions at a depth of 2.8–2.7 km. Minerals of the Pd-Bi-Se system, previously unknown in Bleïda Far West ores, were found in association with native gold: osterboshite (Pd, Cu)₇Se₅, paladsite (Pd₁₇Se₁₅), (Au,Ag)Se, padmaite PdBiSe, native Se, as well as a number of unidentified phases – Pd₂BiSe, Pd₃BiSe, Pd₄BiSe and Pd₅BiSe.

Research subject. Petrophysical zoning of the Blagodatnoye gold-sulfide deposit in the Yenisei Ridge. Aim. To determine indicative petrophysical characteristics of the products of the main occurrence stages and to develop an evolutionary petrophysical model of the investigated deposit.

Materials and methods. Physical fields were studied by the methods of magnetic and electrical exploration and gamma-spectrometry. The petromagnetic heterogeneity and mineralogical-geo chemical features of formation of polymetamorphic complexes, metasomatites and ores were studied by a neutron activation analysis of the content of rare earth and radioactive elements, petrochemical x-ray fluorescence analysis, as well as by an electron-probe microanalysis of pyrite.

Results. The syncollisional fold-overthrust fault (785 Ma) of the preparatory stage provided structural control over the ore-bearing mineral-forming system. The signs of zone dislocation metamorphism include geophysical anomalies: magnetic and natural electrical anomalies due to pyrrhotite and graphite mineralization of cleavage zones on fold limbs, and specific electrical resistance from silicification zones in fold hinges. The metasomatism of the pre-ore (753 Ma) and ore (698 Ma) stages took place under rifting conditions. Pre-ore quartz-muscovite and chlorite metasomatites with carbon mineralization and supra-background Au concentrations were formed under the action of reducing reaction solutions; they remained unaltered in the non-productive part of the deposit. These formations are characterized by elevated concentrations of radioactive elements and natural electrochemical polarizability. During the ore stage, Au was concentrated by fluids with hydro-carbonate-sulfide composition under the violation of the strike-slip kinematics, which caused significant petrophysical transformations of the productive part of the deposit. Early carbon metasomatites in the sub-ore and root sections of the ore bodies were depleted in terms of U, at the same time as retaining their electrochemical activity. Uranium accumulated in the upper horizons of the productive part, whose rocks lost their polarizability due to scattered carbonate mineralization. Magnetic pyrrhotite crystallized as part of sulfides with a regular increase in its proportion in the root sections of the ore bodies. At the final stage (368 Ma), the mineralized zone was broken into a series of blocks with unequal vertical displacements and levels of erosional truncation by upcasts. This led to the exposure of various-depth sections with contrast petrophysical characteristics.

Conclusions. The Blagodatnoye deposit was formed in four stages: preparatory, two ore-generating and final. The petrophysical features of the products of each stage formed the basis for the developed evolutionary petrophysical model, which will be tested on the materials of geophysical studies of the Yenisei Ridge territories.

Research subject. Paleosols discovered in the Kashira sequence of the Pennsylvanian in the southeastern part of the East European platform. Aim. To study the structure and composition of the paleosols.

Materials and methods. Core material from wells was studied by X-ray analysis, scanning electron microscopy and a detailed description of the core and thin sections.

Results. Four types of paleosols were identified, three of which are developed on a dolomite substrate. The dolomites are characterized by the following features: microcrystalline structure with a crystal size of 5–10 microns; predominantly euhedral form of crystals, high intercrystalline porosity (up to 38%), inclusions of in situ halite, gypsum and anhydrite, ubiquitous filaments of sepiolite. In paleosols based on a limestone substrate, beta-calcretes with Microcodium were found. The study of fossil roots (rhizoliths) revealed the correlation between their types and substrate composition. Thus, petrified rhizoliths and root casts filled with sedimentary rock and developed clay cutans were found on a dolomite substrate, while calcite tubules around root channels were developed on a limestone substrate. The latter show the presence of abundant Microcodium formations.

Conclusions. The revealed morphological and compositional features of the paleosols under study, such as the presence of in situ halite and sulfates (anhydrite and gypsum), sepiolite, and beta calcretes, point to the semiarid climate during the Kashira age on the area under study.