Research subject. The southeastern part of the East European Platform and the Caspian oil and gas basin.

Aim. The analysis of the structural and evolutional changes of the tectonic structure of the southeastern part of the East European Platform from the Late Precambrian to the Cenozoic and revealing the cause of the occurrence of a large oil and gas basin in the Cis-Caspian depression.

Materials and Methods. Geological interpretation of seismic profiling data, shown in geophysical fields and reflecting horizons. Areal distribution of rock complexes of different ages according to drilling data.

Results. The history of the southeastern part of the East European Platform is divided into a number of stages. At the end of the Middle Riphean – the first half of the Late Riphean, the Epigrenville supercontinent Rodinia arose (about 1000 million years). The Baltic continent became part of the Rodinia supercontinent. At the end of the Late Riphean – Early Vendian, the Central Russian and Moscow aulacogens emerged, fixing the beginning of the collapse of the Rodinia supercontinent, Cadomian orogeny, and the attachment of Scythia. The Cis-Caspian area turned into a trough, which received a large amount of detrital material from the Cadomian orogen.

Conclusion. The analysis of the tectonic structural changes during the Late Precambrian up to the Cenozoic demonstrated drastic evolution of its structure from a deepsea basin with thin crust to a shallow salt basin. These changes did not occur gradually, but over the course of 9 stages of major structural changes. The ninth stage created the conditions for the emergence of a large oil and gas province in the Caspian region.

Research subject. Lithosphere of the Middle Urals region with increased seismicity.

Aim. Study of the elastic properties and latitudinal zoning of the earth’s crust and upper mantle in the region based on multiwave deep seismic sounding data and the comparison of the identified features of the deep structure with the location of tectonic earthquakes.

Materials and Methods. The gradient velocity sections of the earth’s crust and upper mantle were constructed along the Vizhay– Nizhnyaya Tura–Orsk meridional profile and the fragments of two geotraverses: Kostomuksha–Nizhniy Tagil–Semipalatinsk (Rubin-1) and Nizhniy Tagil–Urengoy (Rubin-2) based on the results of reinterpretation of the Ural deep seismic sounding (DSS) materials using two-dimensional seismic tomography. Sections in isolines of equal velocities were constructed from the first arrivals of compression and shear seismic waves independently of each other and recalculated on the basis of known functional and correlation dependencies into sections reflecting the distribution of a number of elastic parameters in the earth’s crust: density, Poisson’s ratio, Vp/Vs values, bulk and shear modulus.

Results. New data about the deep structure of the Middle Urals region is obtained. Based on materials from the meridional Vizhay–Nizhnyaya Tura–Orsk profile it has been established that the Tagil trough as compared to the Magnitogorsk trough, is characterized by a less thick and higher-speed crust, both in the Vp speed of propagation of compression waves and in the Vs speed of shear waves. At the same time, the Vp/Vs velocity ratio in it is reduced as compared to the Magnitogorsk trough, which indicates greater tectonic disturbance. In the middle part of the earth’s crust a weakened, softened layer is identified, characterized by a reduced Vp velocity of compression waves and reduced Vp/Vs values and Poisson’s ratio. The hypocenters of local earthquakes are mainly confined to this layer. Blocks in the earth’s crust with contrasting density and elastic properties, including latitudinal zones of increased fracturing, have been identified and physically characterized. These zones correspond mainly to latitudinal dislocations, identified earlier according to other criteria, and clarify their location and elastic properties. One of the signs of similar fractured zones cutting across the Ural structures has been identified, namely an increased speed of propagation of shear waves at a reduced speed of compression. The epicenters of Ural earthquakes are confined to the intersection of high-velocity blocks of the earth’s crust of the Tagil-Magnitogorsk trough and Cis-Ural foredeep with identified latitudinal zones of increased fracturing.

Conclusion. The combined interpretation of compression and shear seismic waves made it possible to obtain new data on the deep structure of the Middle Ural region of increased seismicity and to explain the pattern of localization of the epicenters of the Ural earthquakes in this region by its increased tectonic disturbance. The results of the study confirm the geological informational content of multiwave seismicity and can be used in the future to assess the material composition of the earth’s crust, its stress-strain state, development history, as well as for seismic and mineragenic forecasting.

Research subject. The hill morphology formed in the study area, which is part of the Semilir Formation, is suspected to be a product of Opak fault reactivation. Further investigation is needed to substantiate this claim.

Aim. To investigate the characteristics of the Opak Fault in the Semilir Formation. The study area is a red zone, which is an area damaged by the 2006 Opak Fault earthquake.

Materials and Methods. This study was interpreted through integrated data that combined the Digital Elevation Model (DEM) from DEMNAS (Indonesian National Digital Elevation Model), the Digital Outcrop Model (DOM), and extensive field observations. The methodology employed involves investigating DOM interpretation combined with field surveys and morphotectonic methods.

Results. We have identified the study area as divided into two segments: the northern and southern segments. The characterization of these segments is based on the differences in the alignment of landforms associated with the general direction of the hills and analysis from rosette diagrams. In the northern region, elongated hills are oriented in the NE-SW direction, whereas in the south, they exhibit an N-S block lineation. Field observations reveal the presence of a high-angle fault at observation point A (Fig. 6a), indicating reactivation, and a reverse fault at observation point D1 (Fig. 6b). The rosette diagram results indicate a compression direction of NW-SE in the northern segment and N-S in the southern segment.

Conclusions. Integrating UAV photogrammetry and Digital Elevation Model (DEM) data has significantly enhanced our understanding of the geological structures within the Semilir Formation in the Opak Fault Zone. The analysis identifies the study area as a reactivation zone of the Opak fault, indicated by the presence of high-angle reverse faults. This reactivation zone and the landscape morphology consisting of hills are interpreted as a zone of destruction resulting from Opak fault movement, previously identified as a sinistral strike-slip fault.

Research subject. Lower Silurian carbonate deposits in the P-VK6 section (basin of the upper reaches of the Ilych River, Northern Urals).

Materials and methods. The material for the article comprises a field description of a section and 24 rock samples studied by classical optical microscopic and isotopic methods. The extraction of conodont elements from carbonate rocks was carried out according to a standard procedure in 8% acetic acid.

Results. The surface of the sedimentation break is represented by an erosional surface and voids in the microbial laminites. Two types are distinguished among the underground palaeokarst elements: (i) vertical cavities (up to 2.0–3.0 cm) filled with gravitational calcite with fibrous extinction and blocky sparite; and (ii) palaeovoids (5.0–20 cm) with irregular to tube-shaped, filled with laminar clay-carbonate sediments. The first type is located at a depth of up to 2.5 m directly below the surface of the sedimentation break. This interval is also highlighted by the Meteoric Calcite Line isotopic trend (variable δ13C values and invariable δ18O values). The second type is filled mainly with clayey-dolomite material, probably the insoluble sediments derived from rock dissolution. The maximum recording depth for these elements is 5.0 m below the surface of the sedimentation break. Biostratigraphic analysis of conodonts demonstrated that the rocks of the Marshrut regional stage of the Telychian underwent karsting. From the deposits overlying the paleokarst, species Ozarkodina bohemica (Walliser) was determined, which made it possible for the first time to paleontologically confirm the regional gap throughout the Marshrut regional stage of the Llandovery age and Vo`jvyv regional stage of the Wenlock age.

Conclusions. The sedimentation break age, based on biostratigraphic data and regional background, is determined to be Early Wenlockian.

Research subject. Quaternary sediments exposed near the Garevo village and Zhuravsky settlement (latitudinal section of the Pechora River, Ust-Tsilemsky District of the Komi Republic).

Aim. The objective of this study is to reveal the lithological and palynological characteristics and peculiarities of the geological structure of the Neopleistocene sediments.

Materials and Methods. Field observations, including measurements of clast fabric in moraines, were supplemented by the study of sediments by mineralogical, petrographic and palynological methods.

Results. In the consolidated section of Quaternary sediments, three horizons of moraine diamictons and separating them fluvioglacial and interglacial sediments are distinguished. The moraine of the Pomusovka (Oka) glaciation is characterized by the presence of crystalline rocks among the coarse clastic material and its north-northwest orientation. Sands and silts, probably fluvioglacial sediments, separate the Pomusovka sediments from the diamicton of the Pechora (Dnieper) moraine. The Pechora moraine is characterized by an assemblage of boulders without crystalline rocks and an increased proportion of sandstones, siltstones and mudstones. The orientation of the long axes of the debris is multidirectional. The Pechora morainic diamicton is overlain by Rodionovo (Shklov), presumably alluvial-marine (deltaic) sands and lake clays. The clays contain “cold” spore-pollen spectra, indicating the existence of sparse birch forests and shrub tundra at the beginning of the Rodionovo Interglacial. The overlying diamicton of the Vychegda (Moscow) moraine is characterized by the presence of crystalline rocks as a part of a complex of boulders with northeastern, northwestern, and sublatitudinal orientations. The upper part of the section is composed of Laya (Podporozhye) coarse sandy sediments with gravel and pebbles and Polar (Ostashkov) cover silts.

Conclusions. The features of the geological structure and stratigraphic position of the Quaternary sediments in the vicinity of the Garevo village and Zhuravsky settlement in the lower course of the Pechora River have been established. The composite section of Quaternary deposits consists of glacial and interglacial sediments of the Pomusovka, Pechora, Rodionovo, Vychegda, Laya and Polar horizons. Palynocomplexes from the Rodionovo sediments indicate the development of sparse birch forests and shrub tundra at the beginning of the Rodionovo Interglacial. The presence of significantly different ideas about the structure of the sections according to different authors is shown, and the lithological variability of the same age morainic diamictons is noted, which deserves further study.

Research subject. The clay rocks (fine-grained clayey siltstones, shales and mudstones) of the Lower, Middle and Upper Riphean of the Bashkir megaanticlinorium of the Southern Urals (Riphean stratotype).

Materials and Methods. The α^AlE values are calculated for clay rocks based on the bulk chemical composition (major rock-forming oxides and some trace elements), which makes it possible to judge the intensity of weathering of source rocks in catchments. A comparison was made of the α^AlE values characteristic of silts and particulate suspended matter of a number of modern rivers in South Africa, Northern Eurasia and North America, as well as clay rocks of a number of the Riphean formations of the Southern Urals.

Results. The α^AlE curves for clay rocks of the various Riphean formations of the Southern Urals are significantly similar to each other. They are characterized by moderate values of α^AlNa, fairly high values of αAlСa and α^AlSr, and predominantly low values of a number of other α^AlЕs. For clay rocks of most stratigraphic levels of the Riphean stratotype, α^AlNaaverage are close or comparable to those characteristic of suspensions in the rivers of temperate climate. The average αAlK values in shales are also comparable to those calculated for particulate suspended matter in the rivers of temperate climate, for example, the Lena or the Hudson. The silts of the rivers of South Africa, on the contrary, have slightly higher αAlK. At the same time, the shales of the Riphean stratotype have slightly higher α^AlВaverage than the silts of the rivers of South Africa or the particulate suspended matter of the rivers of the temperate climatic zone of Northern Eurasia or North America.

Conclusions. Based on “direct” comparison of α^AlЕ for clayey rocks of the Riphean stratotype and those for silts and particulate suspended matter of a number of rivers in South Africa, Northern Eurasia and North America, we can conclude that the eras of accumulation of terrigenous deposits of the Riphean of the Southern Urals were characterized by a climate reminiscent of the modern temperate climate of the northern hemispheres.

Research subject. Mineralogical, petrological and geochemical features and formation conditions of gabbro-diorites and diorites composing the ore-bearing intrusions of the Kutuevsky Au-Cu porphyry ore occurrence in the Main Uralian Fault zone (Southern Urals).

Materials and Methods. The content of rock-forming oxides was determined by the wet chemistry analysis, trace elements – by ICP-MS (ELAN 9000 mass spectrometer) and ICP-AES (ICPE-9000 atomic emission spectrometer). The study of the chemical composition of minerals was carried out using a Tescan Vega Compact scanning electron microscope with an Oxford Instruments Xplorer 15 energy-dispersive analyzer. P-T formation parameters were assessed using mineral geothermobarometers.

Results and conclusions. The rock-forming minerals of gabbro-diorites and diorites are plagioclase with primary composition close to andesine (An = 32.83–34.43%) and clinopyroxene, represented by augite (Wo_43.9–44.0En_45.2–45.5Fs_10.6–10.8) and diopside (Wo_45.2–47.9En_42.1–44.8Fs_9.2–10.3). Accessory minerals include zircon, magnetite, titanite, apatite, and titanomagnetite. Clinopyroxene is largely replaced by green hornblende (6.956–7.169 a.f.u. Si, 0.73–0.76 Mg/(Mg+Fe²⁺)) of unknown genetic nature. Clinopyroxene crystallization occurred at T = 1010–1072°C and P = 1.35–1.78 kbar. The intrusive rocks of the Kutuevsky ore occurrence and other porphyry occurrences of the MUF zone in the Southern Urals have similar petro-geochemical characteristics that correspond to igneous rocks formed at the early stages of development of ensimatic island arcs. They have a moderate potassium composition, normal alkalinity, calc-alkaline or transitional tholeiitic-calc-alkaline composition. Spinel peridotites of the lithospheric mantle, metasomatized by subduction fluids, are assumed to be the source of magmas for gabbro-diorites and diorites of the ore occurrence. Crust contamination processes also influenced the composition.

Research subject. The Verninskoe large gold deposit (Bodaibo District, Irkutsk Oblast).

Aim. The study of trace and rare earth element distribution in ores and host rocks and the specific features of ore formation.

Materials and Methods. The geochemical features of ores and host rocks of the Verninskoe deposit are studied by X-ray fluorescence analysis and inductively coupled plasma mass spectrometry.

Results. The host rocks are slightly enriched in a wide range of elements (given in the order of enrichment factor decreases): As, Ag, W, Cr, Au, Ni, Cd, Ba, V, Bi, Sc, Sr, Co, Mo, Cs, and Ti. The ores are highly enriched in Au, As, and Ag. The enrichment of the ores in Mo and Bi may be due to the relatively high admixture of these elements in diagenetic pyrite, which is widespread in host rocks. The Sr enrichment indicates its capture from the host calcareous sandstones. The deposition of a significant amount of arsenopyrite in the ores could be due to an additional supply of As from the rocks of the ore-bearing Aunakit Formation enriched in As.

Conclusions. According to geochemical indicator values, the host rocks of the deposit can be classified mostly as shales and graywackes, while a number of samples are represented by Fe-sandstones, litharenites, and sublitharenites. Trace element and REE distribution in the ores indicates the interaction of the ore-forming fluid with the host rocks. The results obtained correspond to the metamorphogenic model of formation of the orogenic gold deposits. The information given in the article is of practical importance for regional metallogenic forecasting and modeling and gold prospecting and evaluation.

Research subject. The studied area is located within the Shchuchinsk zone situated at the northern end of the East Ural megazone. The deposits and ore occurrences of the skarn-magnetite formation known in the Shchuchinsk ore region are grouped into two ore fields, Yunyaginskoe and Talbeyskoe. The Yunyaginskoe ore field is represented by an effusive sedimentary stratum composed of pyroxene porphyrites and pyroxene-plagioclase porphyrites and their tuffs. The Talbeyskoe ore field is located in the gabbroids of the Malyk block, on the contact with early Silurian volcanogenic rocks and is traced submeridionally along the Kharut deep fault.

Aim. Analysis and comparison of the magnetic properties of rocks from the Yunyaginskoe and Talbeyskoe ore fields according to borehole magnetometry by the example of two wells of the Shchuchinsk ore region.

Results. According to the diagrams of rock magnetic susceptibility and the horizontal and vertical components of the magnetic field, the geological section was subdivided, the elements of occurrence were determined and the vertical components of the natural total, residual and induced magnetization of rocks cut by the well were calculated.

Conclusions. The results of borehole magnetometry revealed a wide differentiation of the magnetic properties of rocks of the Yunyaginskoe and Talbeyskoe ore fields. The sources of magnetic anomalies in the Yunyaginsky ore field are thin near-surface magnetic bodies with a high content of magnetite iron. In the Talbeyskoe ore field, the main source of the anomaly is poor magnetite ores (iron content 10–15 wt %) associated with basalt porphyrites filling the syncline formed by skarns. The study of the magnetic characteristics of ore sub-sections made it possible to identify differences in the mineralization types both within the same well and in different ore fields.

Research subject. The flotation tailings of the dump cast slag of the Sredneuralsk Copper Smelter (“SUMZ”) were leached with sulfuric acid at a concentration of 300 g/dm³ at 90°C for at least 15 hours.

Aim. To study the material composition of leaching products of copper smelting slag flotation tailings. Based on the data obtained, we will describe the processes that occurred during the leaching of this type of waste. Material and methods. The methods used were X-ray fluorescence and spectral analysis (EDX-8000 and CPM-35), mass spectrometry with inductively coupled plasma (NexION 300S), powder X-ray diffraction (DRON-3 and D8 ADVANCE), scanning electron microscopy (TESCAN MIRA LMS (S6123) with INCA Energy 450 X-MaxEDS spectrometer).

Results. It has been established that sulfuric acid leaching of copper smelting slag flotation tailings is accompanied by a decrease in the content of zinc, copper, manganese, arsenic and an increase in the sulfur content in the cake, mainly consisting of SiO₂ (32.5 wt %) and Fe₂O₃ (18.0 wt %). X-ray phase analysis of the leaching product revealed the following mineral phases: minerals of the pyroxene group, amorphous silica, gypsum, barite, minerals of the spinel group, sulfides, sulfate forms of ferrous iron, represented by melanterite and ssomolnokite, ferric sulfate – kokimbit, which oxidizes and dehydrates over time, turning into jarosite. According to scanning electron microscopy, the phase composition of cakes is represented by an association of silica, crystalline sulfur, oxygen-containing compounds of iron, lead, zinc, copper and their sulfides. It has been established that zinc is present in all newly formed ferruginous phases. Arsenic is associated with silica. Copper is found in sulfur secretions. Crystalline sulfur is usually found in combination with sulfides. We identified rare earth mineralization represented by cerium, neodymium, lanthanum phosphate, as well as neodymium phosphate in association with niobium and bismuth. The phase composition of cakes is a reflection of the chemical processes occurring during leaching – electrochemical oxidation of sulfides, acid hydrolysis of silicates, ion exchange reactions.

Conclusion. The obtained data on the chemical and mineralogical composition of the products of sulfuric acid leaching of copper smelting slag flotation tailings are of interest for the development of effective methods for their use and disposal, taking into account the ecological consequences for the environment.