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 on the minerageny and mineralization of Riphean rocks in the Bashkir meganticlinorium, one of the largest structures on the western slope of the Southern Urals. The Riphean sections of the western wing of this structure are the stratotype for the Riphean group. Materials and methods. New findings, ideas, and hypotheses on the mineralization and minerageny of the Riphean obtained as a result of long-term work by authors from different regions of Russia were analyzed. Results. The conducted review of various minerageny and mineralization aspects of sedimentary and igneous rocks of the Riphean Bashkir Meganticlinorium showed that over the past 10–15 years, a large number of works have addressed both specific and fundamental issues. As a result, based on a large variety of data (from geological data to isotope-geochemical data), the formation models of large deposits have been proposed. Among the latter are magnesites, siderites, fluorites, Fe–V–Ti ores in differentiated gabbro massifs, etc. Conclusions. The presented analysis provides the reader with a comprehensive overview of contemporary research on diverse types of mineralization in igneous and sedimentary rocks. These include Au, PGE, Au–Pt, Pd–Au–rare-metal assemblages; U- and Th-bearing minerals; complex REE phases; native Ag and its compounds (including furutobeite and Au–Ag sulfoselenoarsenides); as well as Mo-bearing galena and pyrrhotite enriched in Au, Se, and Mo. The review also highlights large and unique deposits hosted within the sedimentary sequences of the Riphean Bashkir meganticlinorium. Many of the studies considered have been conducted to highest academic standards.

Research subject. Structural and tectonic provinces represented by multiple alternations of negative (depressions, grabens, graben-synclines) and complementary positive (uplifts, horsts, horst-anticlines) morphostructures, known as areas of diffuse (dispersed, areal) rifting. The following geological objects are analyzed: the Province of Basins and Ranges (North America), the Selengino-Vitim Zone (Western Transbaikalia), the Sunda Shelf of the South China Sea, the Gissar-Alai and Central Segments of the Tien Shan Alpine Orogen. Aim. To characterize the structure, formation mechanism, and geodynamics of “areal” rift systems, as well as to determine their place in the structure and evolution of the Earth’s crust. Methods. Comparative structural and tectonic analysis of geological objects using remote and experimental research data. Results. The main characteristic features of the structure and evolution of areal (diffuse) rift systems have been established. These include the multiple alternation of troughs (grabens) and uplifts separating them (ridges, mounds, shafts); the spread of the “depression/uplift” paragenesis in the form of wide areas confined to the marginal parts of young and ancient platforms or to intracontinental orogens; the absence of main rift valleys and faults; absence of through-core faults; connection with volumetric loosening and solid-plastic (rheid) flow of basement rock masses within dynamically weakened areas of the Earth’s crust and shear stress field with the regulating role of fractal organization of geological space. Conclusions. The provinces under consideration are paragenetic ensembles of 3D shear and can be morphostructurally defined as “basin and ridge provinces”. Tectonic ensembles of this type are a specific category that is neither structurally nor dynamically analogous to linear rift systems. Linear rift systems are derived from the mechanical splitting and spreading of continental crustal segments (a component of subglobal tectogenesis), while areal systems are the result of brittle–plastic (reid) flow of rock masses within dynamically unstable areas of platforms and orogens (a component of regional tectogenesis).

Research subject. The transverse (sub-latitudinal) structures of the sub-meridional Ural fold belt. Aim. To clarify the nature and age of the transverse structures and their metallogenic significance. Methods and materials. The analysis of geological, tectonic, and structural data on the sub-latitudinal structures throughout the Urals was performed. Results. The current knowledge of the transverse structures of the Urals has been reviewed and generalized. In the West Mugodzhar volcanic zone and the Irgiz synclinorium of the Mugodzhars, geological complexes corresponding to the deeper levels of the Magnitogorsk megasynclinoorium were brought to the Earth’s surface. Such exposure could only have resulted from a vertical uplift of approximately 5–8 km followed by erosion of Paleozoic rocks in the Mugodzhars. In the western sector of the Urals, the structural pattern differs markedly from that in the eastern sector. Here, beginning in the south – where the influence of the Caspian Depression is already pronounced – a gradual northward uplift is observed. This is accompanied by the progressive exposure, at the present-day erosion level, of increasingly ancient complexes, transitioning from sedimentary rocks in the south to metamorphic rocks in the northern part of the Southern Urals. The amplitude of uplift in these metamorphic complexes reaches at least 12 km. Thus, the vertical movements that caused the observed sublatitudinal zonation of the Urals in the south occurred in different directions in its western and eastern sectors. Conclusions. The observed lateral zonation of the Urals is primarily controlled by variations in the present-day depth of erosion across different regions. These variations, in turn, reflect differences in the rates and magnitudes of post-Paleozoic uplift, most notably during the Middle and Late Triassic. Consequently, lateral zonation is only indirectly related to the formation of pre-Mesozoic mineral resources in the region. Nevertheless, understanding the depth of erosion in different parts of the Urals is essential for metallogenic assessments. For younger mineral resources, such as hydrocarbons (oil and gas) and placer deposits, sub-latitudinal zonation plays a decisive role.

Research subject. The geological structure and metallogeny of Northern Algeria. Aim. To investigate the structure and metallogeny of Northern Algeria, part of the Atlas Alpine fold–thrust belt (western flank of the Tethys metallogenic belt), and to conduct their comparative analysis with regions of Russia. Materials and methods. Analytical review of published and archival materials, as well as the fieldwork results obtained by the authors. Results. Using Northern Algeria as a case study, the main patterns in the development of the Alpine fold–thrust belt, controlled by the convergence between the Eurasian Platform and the African continent, are examined. The metallogenic profile of this young fold–thrust belt is dominated by lead–zinc and antimony–mercury mineralization. A comparison of the geological structure and metallogeny of Northern Algeria with other fold–thrust belts of similar age, such as the Mesozoic Verkhoyansk–Kolyma and Chukchi belts, reveals a set of shared features that distinguish these systems from older (Hercynian and Caledonian) belts of the Urals and the Southern Tien Shan. These features include the presence of ancient terrane blocks, the predominance of flyschtype sedimentary sequences, the near absence of deep-marine formations and ophiolites, the large transverse dimensions of thrust sheets, and generally weak metamorphism and structural transformations. Metallogeny also differs markedly.  In these younger belts, the predominantly low-temperature mineralization (Pb, Zn, Sb, Hg) is observed, in contrast to the medium- to high-temperature gold mineralization characteristic of ancient belts. This distinction is likely related to a greater depth of erosion.

Research subject. The Alambay ophiolite zone of the Salair Ridge (northwestern Altai–Sayan folded area, Central Asian Orogenic Belt), belonging to SSZ-type ophiolites. Aim. Determination of the formation age of magmatic rocks in the ophiolite zone. Establishing the age of the paleo-subduction zone initiation and the associated paleo-island arc system. Materials and methods. Zircons from plagiogranite (54°3’50.44” N, 85°45’0.22” E) and gabbro (54°0’46.67” N, 85°47’3.11” E) samples of the Upper Alambay gabbro-hyperbasite massif were dated using LA-ICP-MS on an Agilent 7900 quadrupole mass spectrometer at the Joint Innovation Center for Strategic Mineral Resources Exploration, School of Earth Resources, China University of Geosciences (Wuhan). Results. The weighted mean ²⁰⁷Pb/²⁰⁶Pb age of zircons from the plagiogranite sample (based on 18 analyses with common Pb correction) was 532.2 ± 3.9 Ma (MSWD = 0.84). The corresponding age for the gabbro sample was 530.6 ± 2.7 Ma (MSWD = 0.91). Conclusion. The suprasubduction ophiolites of the Alambay zone (Salair Ridge) formed in the Early Cambrian (≈530 ± 3 Ma). The subduction initiation in this sector of the Paleo-Asian Ocean can be estimated at ≈535–540 Ma. This age serves as a lower constraint for the formation of island-arc volcanic complexes in the Salair sector. Older rock assemblages in the region may represent accreted blocks to the Cambrian arc, likely located southwest of the Alambay zone. Volcanic arc complexes to the east should be younger, consistent with available data.

Research subject. The igneous rocks examined in this study were collected from outcrops located in the vicinity of Sergeevka and Vladimiro-Alexandrovskoye (Okrainsko-Sergeevsky terrane), as well as Kamenka (Kamensky allochthon), villages. The studied jaspers, manganese silicate rocks, and silicate-magnetite ores were sampled from outcrops within the Olginsky and Dalnegorsky ore regions (Taukha terrane) and the Malinovsky ore region (Samarka terrane). Aim. To clarify the geological events in the evolution of the Sikhote-Alin region that determined changes in the geochemical parameters of the Cambrian (?) basites of the Sergeevsky complex. To that end, the petrography, petrochemistry, and geochemistry of the metabasites of the Sergeevsky complex and metamorphosed Triassic metalliferous sediments were studied.  Methods. Gravimetry, inductively coupled plasma atomic emission spectrometry (ICP-AES), and inductively coupled plasma mass spectrometry (ICP-MS) were employed, the latter for the determination of trace and rare elements. The isotopic compositions of Nd, Pb, and Sr were also analyzed. Mineral identification was performed using optical microscopy and subsequently confirmed by compositional analysis with an X-ray spectral microanalyzer (JXA-8100). Results. Analytical data were obtained for metabasites and metaultrabasites of the Sergeevsky complex, including major and trace element compositions and Nd, Sr, and Pb isotopic ratios; their mineralogy and internal structures were also investigated. In addition, analytical data were acquired for jaspers (major and trace elements), as well as for manganese– silicate and silicate–magnetite rocks and ores (trace elements and Nd isotopic ratios) of the Triassic chert formation of the Sikhote-Alin. Conclusion. The obtained data indicate that metamorphic processes significantly influenced the geochemical characteristics of the metabasites. The integrated application of igneous and sedimentary geochemistry, in combination with chemostratigraphic analysis, made it possible to elucidate the systematic variation in paired parameters (¹⁴³Nd/¹⁴⁴Nd– Sm/Nd, ¹⁴³Nd/¹⁴⁴Nd–Y/Nb, and ¹⁴³Nd/¹⁴⁴Nd–Zr/Y) in the metabasites of the Sergeevsky complex, trending toward values characteristic of metalliferous sediments of the Triassic chert formation of Sikhote-Alin. This trend is interpreted as evidence for seawater involvement in metamorphic processes. The involvement of seawater, supported by Sr isotopic ratios in the altered rocks and regional geological data, suggests that diaphthoresis of the Sergeevsky basites occurred during Middle–Late Jurassic accretion.

Research subject. The issues related to the task of correlating the boundaries of Phanerozoic stratigraphic units are discussed. The concepts of chronology, chronometry, zone, zonal method, stratigraphic boundary, marking of stratigraphic boundaries, establishing the chronological identity of stratigraphic boundaries are defined. Material and methods. Criteria for the reliable correlation of stratigraphic boundary division in remote-region sections are specified. Results. The boundary of adjacent stratigraphic divisions established using the zonal biochronological scale is a certain zone. This boundary is the corresponding (eponymous) stratozone in the section. The linear nature of the boundaries of geological objects, determined using the chronological scale, is recorded only on the zonal scale. Real (natural, material) boundaries of geological objects in the section are always volumetric. Conclusions. For the accurate comparison of stratigraphic boundaries, an elementary zonal biochronological scale comprising three zones is required. This scale serves as the primary tool for the identification and correlation of stratigraphic boundaries across all hierarchical levels of the Phanerozoic stratigraphic system. Boundaries of stratigraphic units located in distant sections are considered coeval (chronologically equivalent) provided that they occur within a specific, eponymous stratozone defined using a standard zonal biochronological scale for the corresponding stratigraphic interval.

Research subject. Barremian-Aptian palynomorph assemblage of terrestrial and lacustrine genesis in the Belaya Gora (Semyon) section, Transbaikalia, Chita region. Aim. Based on integrated approach to palynomorph study, to determine the age of the sediments as well as the specific features of paleoflora and its relationship with climatic conditions, paleolandscape and transgressive-regressive fluctuations in the paleolake. Materials and Methods. Samples were processed by a standard technique using heavy cadmium liquid, hydrochloric and hydrofluoric acids. Results. Diverse assemblage of spores and pollen of terrestrial plants of the Turga type is defined, which is strongly dominated by gymnosperms and contains rare angiosperms that is consistent with data from other biofossils. Abundant microphytoplankton of lacustrine genesis is also present. The stages of low and high stands in the lake are determined based on quantitative dynamics of spores, pollen and microphytoplankton. Conclusion. Biofacies analysis of palynological material shows that the sediments were formed in shallow slow-flowing mesotrophic lake surrounded by rich forest vegetation with highly diverse conifers, which is typical for warm and humid climate. Specific features of terrestrial paleoflora and mesotrophic type of the Belogorskoye lake suggest an elevated, but not sharp relief on the surrounding areas. Biostratigraphic range of the section is defined as the Upper Barremian - Lower Aptian. Literature data show that the Barremian-Aptian palynological assemblages of the Turga type are well defined in central regions of Transbaikalia as well as in Mongolia and China.

Research subject. Carbon isotope composition of carbonates and conodont elements in the Upper Visèan–Serpukhovian interval (Lower Carboniferous) in the Polotnyany Zavod and Luzha reference sections in the southwest of the Moscow Syneclise. Aim. To evaluate the possibility of tracing the horizons identified in the basin of the Moscow Syneclise on the basis of data on the carbon isotope composition of carbonates and conodont elements. Materials and methods. Carbon isotope composition was studied in the Upper Aleksin–Protva stratigraphic interval. Carbon isotopic composition of carbonates (δ¹³C_carb) was determined in 14 samples, and that of conodonts (δ¹³C_con) – in 20 samples. Comparative material was obtained from the reference section of the Serpukhovian Stage on the Izyayu River (Tchernyshev Ridge, east of the Pechora Plate). Results. The Upper Aleksin–Tarusa interval is characterised by δ¹³C_carb values of about 1.5‰ VPDB with decreases to –2.6 and –0.2‰ VPDB in the Upper Aleksin and Upper Mikhaylov intervals respectively. A broad “plateau” (values of 1.2–1.6‰ VPDB) covers the upper part of the Venyev and Tarusa horizons. The carbon isotope composition of conodont elements shows a decrease to –30‰ VPDB in the Venev Horizon and an increase to –24‰ VPDB in the middle part of the Tarusa Horizon. In the Steshev Horizon, the δ¹³C_con values decrease to the average values in the section (about –27‰ VPDB). Conclusion. The study of variations in the carbon isotopic composition of conodonts and carbonates in the Upper Viséan–Lower Serpukhovian interval at the Polotnyany Zavod quarry enabled the identification of two correlation intervals characterized by a negative shift in δ¹³C_con in the Venyev Horizon and a positive shift in δ¹³C_con in the Tarusa Horizon. These intervals are also traceable in sections of the Pechora Plate and may be used for interregional correlation.

Research subject. The content of indium in the main mineral associations of tin-polymetallic and polymetallic lead–zinc deposits in Eastern Transbaikalia. Materials and methods. To determine the chemical composition of ore minerals, including indium content in polished sections, samples of sulfide ores containing indium were analyzed using ICP–MS, as well as polarization and electron microscopy. Results and conclusions. Indium content was found to be highly variable both among deposits and mineral assemblages, as well as within individual samples. The average indium content in the studied mineral associations of ores comprises (g/t): tin-polymetallic (Sherlovogorskoye, 244.5, and Khapcheranginskoye, 196.4, average – 234.97 with σ = 238.4) and lead-zinc polymetallic in ascending order of concentrations (Mikhaylovskoye, 71.68; Akatuyevskoe, 87.93; Vozdvizhenskoe, 149.43; Blagodatskoye, 225.4; Noyon-Tologoy, 287.43, average 186.42 with σ = 155.1). The highest average content of indium was detected in tin-polymetallic deposits. The average content across all 32 samples was 200.12 g/t with σ = 183.75. The main carrier of indium was found to be sphalerite, containing up to 0.53 wt % of indium in individual samples of tin-polymetallic deposits and up to 2.06 wt % in individual samples of the Blagodatskoye deposit. The entry of indium into the structure of sphalerite tends to correlate with the characteristics of iron content, and, consequently, with the ratio of zinc to iron; however, its maximum concentrations were observed in the low-iron sphalerite of the Blagodatskoye deposit. The conducted research confirmed and clarified the existing data obtained from the exploration of polymetallic and tin-polymetallic deposits in Eastern Transbaikalia.

Research subject. Mineral assemblages of native gold from carbonatites and Quaternary deposits of the Guli massif (Maimecha–Kotui province, Russia), which are associated with complex gold–iridium–osmium placer deposits. Aim. To identify mineral assemblages and variations in the chemical and Cu-isotopic composition of native gold from calcite– dolomite carbonatite of the Southern carbonatite stock and Quaternary deposits of the Gule River, draining carbonatites of the Guli massif. Methods. The chemical composition of native gold was studied using a CAMECA SX 100 electron microprobe analyzer. The analytical technique for determining δ⁶⁵Cu included dissolving gold samples in a mixture of HCl and HNO₃, selective chromatographic separation of Cu from solution, followed by determination of the ⁶⁵Cu/⁶³Cu value using a ThermoFisher Neptune Plus MC-ICP mass spectrometer. Results. The analyzed samples are represented by single-phase and polyphase mineral assemblages of native gold within homogeneous and heterogeneous grains, which consist of high-fineness gold, electrum, natural Au–Ag–Cu alloys, tetra-auricupride, and auricupride. The first Cu-isotope data for gold minerals from calcite-dolomite carbonatite of the Guli massif and Quaternary deposits of the Gule River revealed identical, within analytical uncertainty, average δ⁶⁵Cu values (−0.49 ± 0.08‰ (n = 3) and −0.30 ± 0.30‰ (n = 8), respectively). Conclusions. The observed features of the mineral assemblages and the chemical composition of native gold from calcite–dolomite carbonatites show a close similarity to those of placer deposits of the Gule River, located near the Southern Carbonatite Stock. Copper isotopic data for both primary and placer gold are consistent within analytical uncertainty, suggesting a common juvenile source. It is proposed that the principal bedrock sources of gold were rocks of the Maimecha–Kotui ijolite–carbonatite complex.