Research subject. Deep structure of the earth's consolidated crust of the paleorift system of the White Sea and the Mezen syneclise.

Materials and methods. Two-dimensional seismic density models of the earth's crust structure were constructed on the basis of the 3-AP (Kem–White Sea–peninsula Kanin), Agat-2, Agat-3, and Quartz 2 reference seismic profiles. The state of the deep layers of the earth's crust was interpreted using the distribution of the effective density of the substrate and a model of distribution of magnetic anomalies sources. The latter model was constructed using the technique of two-dimensional inversion of an anomalous magnetic field. The magnetic field was analyzed based on a schematic map of magnetic field anomalies (AMP), synthesized by the authors based on the materials of magnetic surveys carried out in the waters of the Barents and White Seas at different time points and provided for their further interpretation. The main objective of constructing geological and geophysical models of the deep structure of the earth's consolidated crust of the White Sea paleorift system and the Mezen syneclise was to establish genetic relationships between near-surface geological structures and deep elements of the earth's crust structure.

Results. The conducted analysis of the abovementioned materials, taking into account the data on the near-surface structure of the earth's crust, allowed geological and geophysical models of the earth's crust to be constructed to the crust-mantle level along four reference seismic profiles – 3-AP, Agat-2, Agat-3, and Quartz-2 – crossing the structure of the Mezen syneclise in different directions. In addition, in the eastern part of the Mezen syneclise, a series of magnetic profiles is presented, demonstrating the confinement of the AMF sources to two hypsometric levels in the territory where the Late Paleozoic Mezen trap-dyke field, located in the sedimentary cover, was previously described.

Conclusions. Joint interpretation of seismic density models and those of distribution of magnetic anomaly sources made it possible to establish connections between physical parameters of models and geological structures or bodies and to create generalized geological and geophysical models of the studied areas of the earth's crust. According to the constructed 2D models of the deep structure of the earth's crust of the Mezen syneclise, the earth's crust has a complex and heterogeneous structure. The complex mosaic picture presented in the obtained models reflects the layered-block structure of the lithosphere. The block structure of the Mezen syneclise basement is mainly formed by riftogenic faults that limit grabens and horsts of the paleorift system of the White Sea and separate blocks with different density properties. The main structure-forming faults are listric in nature and flatten out toward the base of the upper or middle crust, acquiring detachment properties at depth. A certain correlation of the Moho surface relief with the structures of the surface layer of the earth's crust is noted. The distribution of deep sources of the anomalous magnetic field in 2D format for the low-frequency component of the magnetic field also reflects the structure of the earth's crust in the western part of the Mezen syneclise. Intense long-period magnetic anomalies here most likely reflect the saturation of the products of basic-ultramafic magmatism in the upper granite-metamorphic layer of the earth's crust.

Research subject and methods. A comparative analysis of the author’s and literature data on the zoning of lithogenesis and cryogenesis processes in soils of the central area of the East European Plain was carried out. The study sites are located in the periglacial zone of the Valdai glaciation, concentrated around three soil zones of six subjects of the Russian Federation. A set of methods, including cartographic, morphological, stratigraphic, comparative geographical, and the 14C-method for dating soil samples, was used.

Aim. To identify the features of manifestation of the Late Pleistocene processes of pedogenesis, lithogenesis, and cryogenesis in the central area of the East European Plain.

Results. For the first time, the use of an integrated methodological approach made it possible to obtain results in a wide geographical aspect and generalize data demonstrating the varying degrees of the Late Pleistocene processes of cryogenesis, lithogenesis, and pedogenesis in the soils of the central area of the East European Plain. Here, paleocryogenic microrelief, paleocryogenic phenomena, and paleosoils of the Middle Altai period were identified and systematized. These soils possess different morphogenetic features, lie at different depths, and are buried by sediments of different thickness, reflecting the zonal specificity, time, and speed of lithogenesis and pedogenesis. From the Middle Valdai stage up to the present, the impact of the Valdai glacier has ensured the gradual change and intensity of natural processes in the periglacial region from the peripheral part to the glacial part. Since the onset of the formation, flourishing, and degradation of the ice sheet, the processes of pedogenesis, lithogenesis, and cryogenesis, and again lithogenesis and pedogenesis, have changed at different times and with a varying intensity of manifestation in different central areas of the East European Plain. In the chernozem zone, the processes of pedogenesis, lithogenesis, and cryogenesis occurred somewhat earlier than in the humid regions, with the latter process being insignificant and short-lived. The territory of the gray soil zone was dominated by the maximum development and impact of the glacial cover, which was reflected in the processes of intensive lithogenesis and the most extreme conditions of cryogenesis processes. In the zone of sod-podzolic soils, cryolithopedogenesis processes in different epochs were short-term, which was likely due to the dynamics of the existence and degradation of the glacial cover, manifested in a shortage of transported mineral material, as well as to the weakening and shortening of cryogenic processes.

Research subject. Research articles and notes published during the period from 2010 to October 2024 and available at the Scientific Electronic Library on the eLibrary.ru platform, presenting the results of studying zircon from igneous complexes and detrital zircon, tectonics and geodynamics, magmatism and metamorphism of the Bashkir meganticlinorium. This is one of the largest structures on the western slope of the Southern Urals, which is a stratotype locality of the Riphean.

Materials and methods. New findings, concepts, and ideas on the age and features of the evolution of igneous complexes based on precision dating of magmatogenic zircon obtained by a large group of authors over long-term work were reviewed. New ideas on the age, composition, and evolution of detrital material sources, presented for the first time in a multifaceted manner using sandstones of a typical locality for the Riphean, are considered. The article discusses modern achievements in the study of the geodynamics of magmatic and sedimentary associations of the Riphean in the Bashkir meganticlinorium, presenting modern publications on magmatism, metamorphism, and ore genesis processes.

Results. The conducted review of the current knowledge in the field of the Riphean geology of the Bashkir meganticlinorium showed that, in recent years, many works have appeared, some of which address specific issues and facts, while some can be considered as those opening new pages of research. These works will determine the direction of research in this field in the coming years.

Conclusions. The critical analysis of the publications considered in this review made it possible to obtain a visual representation of the modern data on “zirconology”, geodynamics and tectonics, magmatism and metamorphic processes in the Riphean stratotype area on the western slope of the Southern Urals. In many respects, these studies are at the current level of similar works in the world. Among them, there are areas that require support and care, and there are those where breakthrough achievements can be expected.

The search for and substantiation of geochronological standards, as well as their interlaboratory testing, are current tasks in the field of analytical geochemistry. Zircon Bai-1-2023 from the sands of the bays of Lake Baikal (“Peschanaya Bay”), a product of the destruction of rapakivi granites of the Primorsky Complex of the Western Cis-Baikal region, has been proposed by the Institute of the Earth’s Crust SB RAS as a U–Pb geochronological standard. Results. This paper presents the results of an interlaboratory, “blind” U–Pb and Lu–Hf isotope study of more than 100 Bai-1-2023 zircon grains. Grain composition, texture, and homogeneity were analyzed by the methods of microprobe and LA–ICP–MS analysis, local Raman and cathodoluminescence spectroscopy. The results were compared with those obtained for international reference materials of zircon Mud Tank, 91500, Temora-2, GJ–1, and Plesovice. For 25 grains (37 LA–ICP– MS determination rounds), two statistically isolated, concordant age populations of 1871 ± 8.1 and 1781 ± 5.7 Ma were identified; for most points, the discordance parameter for ²⁰⁷Pb/²⁰⁶Pb and ²⁰⁶Pb/²³⁸U ages was less than 5–6%; for single ones – 10–17%. One population showed an age close to IR-TIMS dating (1859 ± 16 and 1853.6 ± 6.5 Ma). The presence of two populations  is not accompanied by clearly distinguishable changes in the composition of zircon grains and their texture, cores, shells, and cracks. LA–ICP–MS data were obtained for ¹⁷⁶Hf/¹⁷⁷Hf and ¹⁷⁶Lu/¹⁷⁷Hf isotope ratios. The parameter εHf_(t) and the model age of the source T_DM were calculated as follows εHf_(t)= –13.7 ÷ –6.5 and T_DM = 2.5– 2.7 Ga. For zircon grains, significant variations in the position of the vibrational mode ν₃(SiO₄) (1003.4– 1006.6 cm^-1) and its width FWHM  (4.8–9.8 cm^-1), as well as the values of accumulated autoradiation and equivalent doses – (0.64–2.47) and (0.20– 0.52)·10¹⁸ α-decay/g, respectively, were established. Bai-1-2023 zircon was shown to correspond to II–III stages of the mineral disorder. Cathodoluminescence brightness of zircon grains varied by more than an order of magnitude. In the spectra, a number of broad bands A_i, B_i, C_i in the near UV, blue–green, and yellow regions were distinguished. The position of points for Bai-1-2023 zircon on the triple A_i–B_i–C_i discrimination diagram was analyzed. Spectroscopic properties of Bai-1-2023 zircon and the degree of its radiation damage were shown to overlap the properties of the reference materials  91500 → Temora-2→ GJ–1 → Plesovice. Conclusions. Zircon Bai-1-2023 can be recommended as a secondary age reference material for verifying the accuracy of LA–ICP–MS analysis.

Research subject. Paleozoic carbonate complexes in the offshore area of the Timan–Pechora oil and gas basin. 
Aim. To evaluate the possibility of using data on the isotopic composition of carbon and oxygen in carbonate rocks for the interpretation of depositional environments and stratigraphic correlation of geological sections.

Materials and methods. Within the framework of the RN-Shelf-Arctic LLC (RNSHA) regional projects focused on a geological study of offshore areas, the isotopic composition of carbon and oxygen of Paleozoic carbonate deposits from the core of five wells were analyzed.

Results. The value of δ¹³C_carb increases up the section from -5.9‰ in S₂ to 6.0‰ in P₁a-s. The most significant weighting of δ¹³C_carb from -1 to 6‰ occurred in the Upper Carboniferous interval. The variations of δ¹⁸O_carb from 23 to 33‰ are characterized by the absence of a general trend along the section combined with more frequent and abrupt excursions, which are most pronounced in the Carboniferous.

Discussion and conclusion. Four local factors of isotopic variations were considered, including mineral, facial, post-sedimentary, and stratigraphic. Two of them – depositional environments and secondary (postdepositional) changes – are regarded as the major factors, being controlled in varying degrees on different stages by either local or global factors. The final result of their influence was integral and expressed by the “stratigraphic” curve of isotopic composition variability.

Research subject. To present new results obtained when studying clayey-carbonate deposits of the Sizim Regional Stage of the Upper Ludlow in the Silurian reference section on the western slope of the Subpolar Urals.

Materials and methods. Representative collections of sedimentary rock samples with fossil fauna collected by the authors from Upper Silurian deposits in different years during fieldwork on the western slope of the Subpolar Urals, the Chernov and Chernyshev Uplifts, as well as new C-isotope data, were used.

Results. For the first time, a biostratigraphically dated interval with positive δ¹³C values marking the Middle Ludford Lau isotope event in the Upper Ludlow section of the Subpolar Urals has been distinguished. The isotope curve has a stepped structure and records a distinct positive trend. The previously determined positive isotope excursion of the Early Pridolian Klev Event at the base of the Belush’ya Regional Stage of the Pridoli marks the boundary of the Ludlow and Pridoli in the same section of the Subpolar Urals.

Conclusions. The conducted integral study of successive changes in facies, biota composition, and behavior of stable carbon isotopes in the Sizim Regional Stage section on the western slope of the Subpolar Urals made it possible to identify the manifestations of the global biotic and isotopic Middle Ludford Lau Event.

Research subject. Collection of thin sections containing foraminifera of the Lower Visean Substage of the lower section of the Syrtinsky carboniferous system, located on the left bank of the Ural River to the northwest of the Syrtinsky village within the Shartym–Kizilskoe–Urtazym district, Magnitogorsk structural-facies megazone of the Southern Urals eastern slope. The collection, founded by T.V. Pronina, is stored at the Laboratory of Stratigraphy and Paleontology of the Institute of Geology and Geophysics of the Ural Branch of the Russian Academy of Sciences in Yekaterinburg (Russia). From this locality, the holotype of the Permodiscus (?) primaevus species, Pronina, 1963 comes from, which is one of the zonal taxa of the Lower Carboniferous foraminiferal sequence. Aim. Comprehensive characterization of the foraminiferal community containing this taxon and clarification of its systematic position taking into account all the latest research on this issue. Materials and methods. Micropaleontological studies of the collection of thin sections from the location of the Permodiscus (?) primaevus holotype. Results. A comprehensive paleontological characterization of the microfauna complex from the Syrtinsky location was carried out; the facial confinement of carbonate deposits in the location was considered. The studied foraminiferal association contains numerous taxa typical of the Early Visean interval of the section. The presence of archaediscids of the Ammarchaediscinae subfamily, including the Permodiscus (?) primaevus holotype, in the absence of representatives of the Uralodiscus genus, makes it possible to attribute this complex to the Viseidiscus primaevus–Eoparastaffella subglobosa zone, which characterizes the Burlin regional substage of the East Ural subregion. A systematic description of the Viseidiscus genus and its type species is given, along with some representatives of the Eoparastaffella genus, Pseudoendothyridae family, such as E. tumida, E. florigena, E. expleta, first isolated by T.V. Pronina in the deposits of the Lower Visean substage and encountered in this locality. Conclusions. The representative association of foraminifera, including zonal species, allows the stratigraphic position of the host rocks to be unequivocally determined. The deposits with this foraminiferal complex are widely traced in the Lower Visean carbonate formations of the Urals western slope, in the Don–Dnieper region, in the Franco–Belgian stratotype, where it corresponds to the Mississippian Foraminiferal zone MFZ10, and in other regions of Eurasia.

Research subject. The Svetlinskoye gold–telluride deposit, the largest operating deposit in the Southern Urals, localized within the Svetlinskoye thrust zone of the Kochkar Anticlinorium.

Aim. To develop a new geological-genetic model of the deposit based on the results of long-term research at the Svetlinskoye open pit.

Materials and methods. The results of geological and structural observations in the open pit, geochemical and mineralogical research, ⁴⁰Ar/³⁹Ar isotopic dating of potassium-bearing minerals were analyzed. A review of literature sources was conducted.

Results. The formation of the deposit was preceded by the emergence of a deep thrust (D₃) related to the onset of the Uralian collision, which destabilized the geological environment. The tectonic couple “thrust–buckling” was in operation, leading to the formation of the Anticlinorium, heating of rocks in its core, plastic and quasi-plastic deformations, growth of dome structures, zonal highgradient metamorphism, and deep metasomatic alterations of rocks. At early stages, a shallow marine basin emerged in the footwall of the thrust, accumulating terrigenous-carbonate sediments with numerous submarine landslide phenomena. The marine basin closed in the С_1v due to the formation of the Anticlinorium and uplift of the territory. The Svetlinsky dome, on whose western slope the deposit is located, played a key role in the localization and transformation of the ore cluster. The growth of the dome led to the deformation and partial destruction of the thrust zone, forming systems of tectonic detachments (thrusts), which became the main fluid-conducting and ore-hosting structures. Dome formation, zonal metamorphism, and granitization were associated with the mobilization and redistribution of ore components (Au, Te). The main ore-forming processes occurred at the early post-collisional stage, in the interval of 289–277 Ma.

Conclusions. The structural preparation and ore-mobilizing processes during the formation of the Svetlinskoye deposit took place at the collisional stage (380–290 Ma), while ore deposition and deposit formation occurred in the interval of 289–277 Ma. The Svetlinsky dome played the main role in the formation and localization of the deposit; its formation was likely related to the emergence of deep thrusts under the conditions of the Late Paleozoic collision. This model provides a satisfactory explanation for the gold mineralization of periand inter-dome structures in the Kochkar Anticlinorium, thus indicating their priority for prospecting.

Background. Icy quartz and gondites of the Borussian ophiolite belt (Western Sayan Mountains) are promising as jewelry and ornamental raw materials and industrial stone materials for various purposes; however, these deposits have been poorly studied.

Aim. To investigate the structural and material composition of icy quartz and gondites of the Borussian ophiolite belt and to determine their applicability in jewelry production and as industrial stone materials. 

Materials and methods. Samples of icy quartz and gondites from the Western Sayan Mountains were provided by TomGDK LLC. The structure and mineral composition of rocks were determined by optical methods in polished thin sections. The chemical composition of samples was determined by X-ray fluorescence analysis (XFA). Individual minerals were studied by scanning electron microscopy using a Jeol JSM-6390LV microscope equipped with an INCA Energy 450 X-Max 80 energy dispersive attachment. The mineral composition of microquartzite and gondite was assessed by X-ray analysis performed at the Common Use Center “Geoanalyst” of the Institute of Geology and Geochemistry of the Ural Branch of the Russian Academy of Sciences (Ekaterinburg).

Results. Icy quartz is a massive, fine-grained quartzite of almost monomineral composition with minor admixtures of chlorite, fluorapatite, and calcite. The best varieties transmit light to a depth of 10 cm or greater. Gondites are represented by the same microquartzites of a coarse-banded texture; they are characterized by abundant inclusions of almandine-spessartine. These exhibit signs of shear deformations and recrystallization, which caused the formation of banding and small folds of drawing. The ornamental and mechanical properties render icy quartz and gondite suitable for jewelry, glyptic, and souvenir production. The purest (free from mineral impurities) icy quartz is similar in its characteristics to such an expensive abrasive material as Arkansas stone.

Conclusions. Due to their decorative qualities and mechanical properties, icy quartz, gondites, and black microquartzites of the Borussian ophiolite belt can be used for jewelry, glyptic, and souvenir production. Icy quartz, free from mineral impurities, can be used as an abrasive material, such as Arkansas stone.

Research subject. Various carbonate spherical formations having shells of different compositions and forming clusters in the composition of limestone fragments in metagravelites of the flyschoid black shale section of the Vendian hanging wall of the ore-bearing structure of the Kumtor deposit.

Aim. To assess the entire diversity of the population of carbonate spherules with similar shells, from the point of view of establishing possible variants of the nature of their formation and the material composition of the spherule shells.

Materials and methods. A series of sections of the Vendian flyschoid black shale sequence of the hanging wall of the ore-bearing structure of the Kumtor deposit with horizons of specific metagravelites containing carbonate fragments with clusters of spherules was studied. Samples of metagravelites from borehole cores were studied by optical methods, with diagnostics of mineral formations in thin sections, polished sections and polished sections. A scanning electron microscope (SEM) was used to work with one of the samples. Individual areas of the polished thin section were analyzed to obtain energy-dispersive X-ray spectra (EDS) and multi-level elemental EDS maps.

Results. Metagravelites are observed as a marker horizon in the composition of the terrigenous rhythmite sequence – flyschoid interbedding of carbonaceous phyllites, psammitic phyllites, and polymictic sandstones with carbonate cement in the section of rocks of the hanging wall of the ore-bearing structure of the Kumtor gold deposit. In the composition of most carbonate fragments of metagravelites, various spherical formations with individual sizes, external shells and, often, internal structure were found. They form clusters of different density, the distribution of which does not go beyond the carbonate fragments in metagravelites. In the composition of the studied external shells of spherules, the presence of titanium in the mineral form of rutile has been established to date.

Conclusions. The observed spherules belong to syn-, diagenetic formations of pelitomorphic carbonate sediments, destroyed and redeposited later as gravel-sized limestone fragments in terrigenous sediments of a later age, which were subsequently metamorphosed. Based on their appearance and size, such spherule clusters were initially classified as peloids in carbonate rocks. However, the presence of specific external shells in all spherules, the diversity of their shapes and sizes, and, in some cases, their internal structure suggest the presence of objects of biological nature among them. The formation of mineral “titanium” shells around spherules within carbonate fragments occurred either during regional metamorphism or is associated with diagenesis of carbonate sediments containing spherules of biogenic origin with elevated titanium contents. These mineral shells contributed to the preservation of spherule shapes during subsequent transformations of terrigenous rocks under greenschist metamorphism.

Research subject. Products of salt weathering on limestone building blocks of the Hussein-Bek Mausoleum, located in the Chishminsky District of the Republic of Bashkortostan.

Materials and methods. The composition of salt weathering minerals was studied using X-ray phase, electron microscopic, energy-dispersive, and mass spectrometric analysis methods.

Results. In the efflorescences, the following main minerals were found: gypsum CaSO₄ × 2H₂O, hamberstonite K₃Na₇Mg₂(SO₄)₆(NO₃)₂ × 6H₂O, darapskite Na₃(SO₄)(NO₃) × H₂O, syngenite K₂Ca(SO₄)₂ × H₂O, epsomite MgSO₄ × 7H₂O, kieserite MgSO₄ × H₂O, glauberite Na₂Ca(SO₄)₂, dolomite CaMg(CO₃)₂, and celestine SrSO₄. The sulfur isotope composition (δ³⁴S) of the efflorescence minerals ranged from +7.28 to +11.38 ‰ V-CDT. Samples with hamberstonite and darapskite were characterized by light isotope enrichment, which is apparently associated with the biotic impact of bird guano.

Conclusions. The main mechanism leading to destruction of the building stone of the HusseinBek Mausoleum was established to be salt weathering of the cement caused by the crystallization of authigenic minerals. The salt weathering of the Mausoleum is ornithogenic in nature, caused by the activity of birds, primarily field sparrows (Passer montanus).