Vol 25, No 1 (2025)

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. 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. 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 αAlE 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 αAlE 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 αAlE 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 αAlNa, fairly high values of αAlСa and αAlSr, and predominantly low values of a number of other αAlЕs. For clay rocks of most stratigraphic levels of the Riphean stratotype, αAlNaaverage 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 αAlВaverage 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 αAlЕ 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. 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 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.