Research subject. The clayey rocks of the Vendian Serebryanka and Sylvitsa groups on the western slope of the Middle Urals.

Material and methods. The research materials comprised data on the content of main rock-forming oxides in clayey rocks (mudstones, shales, fine-grained clayey siltstones, ≈180 samples in total) with the values of losses on ignition <6 wt %. This information, obtained at the beginning of 2000 by the X-ray fluorescence method at the Institute of Geology and Geochemistry, Ural Branch of RAS, was used to calculate the average, minimum and maximum values of various weathering indices. Samples were taken from natural outcrops in the basins of the Chusovaya, Serebryanka, Sylvitsa, Mezhevaya Utka, Usva and Koiva rivers.

Results. It was established that the sedimentary sequences of the Serebryanka and Sylvitsa groups, in which diamictites are present at several levels, do not exhibit a noticeable contrast in the values of various chemical indices of weathering. For example, taking into account the values of standard deviations (±1σ), the values of the Ruxton coefficient for all nine Vendian formations are statistically comparable. The same is characteristic of the average values of CIA, CIW, PIA, ICV and MIA(o) for clayey rocks of different formations. Variations in the average CPA values show that, taking into account ±1σ, only the rocks of the Starye Pechi, Garevka and Perevalok formations can be considered statistically different. Taking into account ±1σ, the clayey rocks of the Buton Formation differ significantly from the fine-grained clastic rocks of the Garevka and Kernos formations in terms of the average value of the Mg-index. The clayey rocks of the Tanin and Kernos formations have a weak or moderate positive correlation between the TiO₂/Al₂O₃ ratio and the Ruxton, PIA, ICV indices and the hydrolyzate modulus. This suggests the dependence of the listed indicators of the intensity of weathering from the composition of rocks in paleocatchments.

Conclusions. The data obtained suggest that, when averaging at the level of formations (even if the formations include quite a lot of undoubtedly glaciogenic deposits), we apparently do not record the specific contribution of the latter and, as a result, we obtain a substantially different picture than that which emerges for other Neoproterozoic deposits, including diamictites, varved clays, and intervals with dropstone.

Research subject. The transformed clastic ores (ore diagenites) of the Ishkinino Co-bearing massive sulfide deposit hosted by serpentinites of the Main Uralian Fault Zone.

Materials and methods. The structures and textures of the ores were stu died. The trace element contents of sulfides and oxides were determined using LA ICP MS. The physical and chemical modeling of the diagenetic formation of accessory As minerals was conducted using the Selektor program package. 

Results. The clastic ores are transformed gravelites with angular and rounded clasts of serpentinites, sulfides and chromite in the psammitic matrix of the same mineral composition. No hydrothermal minerals remain in gravelites; they are replaced by crystalline pyrite-2, porous pyrite-3, anhedral pyrite-4, pyrrhotite, chalcopyrite and magnetite. Chalcopyrite and magnetite replace all sulfides, sulfarsenides, chromite and gangue minerals. Chromite occurs as fragmented crystals or inclusions into serpentinite clasts. The matrix hosts euhedral cobaltite crystals with nickeline, gersdorffite and native gold inclusions. Crystalline pyrite-2 is characterized by higher Mn, Co, Ni, Cu and Zn contents. Porous pyrite-3 exhibits higher Co, Cu and Se contents. Anhedral pyrite-4 is enriched in most trace element contents in comparison with other sulfides and pyrite generations. Chalcopyrite is characterized by higher contents of Zn and Se. Pyrrhotite contains the highest Ni and hi gher Co contents.

Conclusions. The main trace elements in the ores of the deposit (Co and Ni), as well as Cu, Zn and Mn, are hosted not only in sulfides, but also in oxides. Thus, chromite contains Zn and Ni, while magnetite contains Mn and Cu. Selenium occurs in all sulfides in similar quantities. Tellurium is mostly concentrated in pyrite-4. A comparative analysis of our results with those reported on other massive sulfide deposits showed that the serpentinite-sulfide gravelites of the Ishkinino deposit had been intensely transformed during diagenesis, which resulted in low trace element contents in diagenetic sulfides. The diagenetic alteration of clastic ores led to the formation of authigenic cobaltite, gersdorffite, nickeline and native gold as a result of trace element release from primary hydrothermal minerals. Thermodynamic mode ling showed the possibility of formation of As-bearing minerals (in particular, nickeline) at temperatures of 200°C and below.

Research subject. Detailed mineralogical and geochemical studies of rocks of the Tukan gold-quartz deposit (quartz veins, dolerites, gabbro-diorites) were carried out. The deposit is one of numerous small gold-quartz occurrences in the Khudolaz trough of the West Magnitogorsk zone.

Methods. The morphology and composition of native gold was studied using an Axios kop 40 A optical microscope and Tescan Vega 3 and JEOL-6390LV scanning electron microscopes. The chemical composition of rocks was determined by X-ray fluorescence (Carl Zeiss VRA-30) and atomic emission (Shimadzu ICPE-9000) analyzes. Fluid inclusions were analyzed using Linkam TMS-600 thermostage equipped with Link-System 32 DV-NC software and an Olympus BX51 optical microscope. The gas composition of fluid inclusions was examined by Raman spectroscopy (Horiba LabRam HR800 Evolution).

Results. Gold-bearing quartz veins and dolerites intersect ing the gabbrodiorite intrusion of the Khudolaz complex are associated with submeridional strike-slip faults. Native gold has a various morphology and is confined to cracks in quartz veins and altered dolerites. The composition of gold is stable, with the average fineness of 871 ± 8.3‰. An analysis of fluid inclusions in a gold-bearing quartz vein showed that gold was formed at temperatures of no less than 186–230°С from a fluid with a salinity of 4–8 wt % NaCl-eq. The presence of gases СО₂, N₂ and CH₄ was found in fluid inclusions. Dolerites and gabbrodiorites hosting gold-bearing veins contain sulfides (pyrite, pyrrhotite, chalcopyrite, pentlandite, violarite), sulfoarsenides (cobaltite and its analogs), as well as mine rals of Ag (hessite) and Pb (kuranakhite and phases similar in composition to minerals of the dugganite group and burckhardtite). 

Conclusions. The sustained composition of native gold and a narrow range of salinity and homogenization temperatures of fluid inclusions indicate the formation of gold during a single stage of mineralization. The main source of gold could have been the dolerite dikes of the Ulugurtau complex. The presence of CO₂, N₂ and CH₄ gases in fluid inclusions from goldbearing quartz indicates that not only magmatic fluid, but also fluid from the host rocks took part in mineral formation. The low value of the ratio X(CO₂)/X(CH₄) ≤ 0.7 indicates a moderately reduced ore-forming fluid. Low Au concentrations (0.1– 0.4 ppm) in quartz veins, dolerites, and gabbro-diorites, including those containing visible gold, indicate a weak commercial potential of the deposit

Research subject. The Verkhnekamskoye potash salt deposit located in the Pre-Ural trough, deformation structures inside the salt rock mass associated with the influence of the Ural orogen.

Materials and methods. A complex interpretation of gravimetric and geological data, including those obtained via well drilling, was carried out. The materials obtained during the processing of gravimetric data in the VECTOR system were used. Based on the relationship between gravity anomalies and density differentiation, the shape and size of the studied objects, as well as their mutual position, were characterized.

Results. The use of modern processing and interpretation methods of gravimetric data allowed us to detect dislocations of different kinematics formed under the influence of a force field originated from the collision structure of the Urals. In the course of tectonic processes in the geodynamic environment of horizontal compression, post-sedimentation structures were formed inside the salt strata, which complicate the internal structure of the salt-bearing formation. Possessing high plasticity and low strength properties, the salt formation represents an autonomous geodynamic system in the force field of the PreUral deflection, where mechanical stresses arising under the influence of the Ural collision zone were implemented as deformation structures. The results of the tectonic evolution of the salts are steadily revealed by anomalies in the gravitational field.

Conclusion. Using the gravimetric method, we identified structures inside the salt rock mass under study, which were produced under the dynamic action of the Urals as a response of the geological environment to the force filed.

Research subject. Deformations and stress state of rock masses at subsoil use objects.

Materials and research methods. Extensive experimental data about the relative deformation of matter and, in particular, about the deformation of rock masses (earth’s crust) allowed the authors to find a solution to this problem using the very behavior of the rock mass during its response to technogenic activity.

Results. Novel results were obtained on the relative deformation of matter under the conditions of changing external factors: 1) deformation of rock mass itself; 2) deformation of a surveying tape as a measuring instrument, 3) deformation of a quartz tube in a deformometer as a measuring instrument. Using the results of measurements over the 11-year nanocycle of solar activity available to us, regularities in the emergence of deformations and stresses of rock masses were revealed. A justification was obtained for changing the physical state of measuring instruments based on electromagnetic waves: satellite navigation systems, light and radio range finders. At the same time, it was found that all these parameters change in time continuously and endlessly, thereby requiring constant monitoring for making a reliable forecast of their impact on technogenic activity.

Conclusion. The results presented in the article extend previous publications of the authors, the main conclusions of which are as follows. 1. The results about the deformations of rock masses, which are currently being obtained by methods based on various physical principles, are relative; therefore, these results do not allow one to judge about their absolute values. 2. The international community of scientists should develop a mechanism for tracking changes in the deformations and stress state of rock masses.

Research subject. The relationships between heat fluxes and ground surface temperatures in a diurnal cycle.

Methods. Experimental studies, including actinometric observations and monitoring of surface temperatures and surface heat fluxes for a soil and an artificial layer, were performed at the Verkhnee Dubrovo meteorological station in 2020.

Results. The surface heat flux varies synchronously both with the total solar radiation near the earth’s surface and insolation at the upper boundary of the atmosphere. Maximal values of these heat fluxes are observed at the solar noon. The temperature response lags behind them by the time interval determined by the soil’s thermal heterogeneity. In this study, we extend our model of the ground surface temperature response to external radiative forcing, which was developed earlier, to the case of a thermal inhomogeneous half-space. An analytical expression for the simplest case of inhomogeneity (the presence of an upper layer with thermal properties different from those of the underlying rocks) is given and investigated. If the upper layer demonstrates a reduced thermal conductivity, the phase shift between the heat flux and the temperature response decreases in comparison with the value for a homogeneous half-space (45°).

Conclusion. The soil studies conducted at the “Verkhnee Dubrovo” meteorological station allowed us to construct a thermophysical section and to verify the previously developed model using experimental data. The errors of theoretical estimates, in general, do not exceed those of the phase estimate at a 10-minute sampling rate. The obtained results can be applied when conducting climatic (including palaeoclimatic) and environmental studies, as well as when investigating heat exchange processes on artificial urban surfaces and their role in the formation of urban heat islands.

Research subject. The article presents the results of a comprehensive study of a column of organomineral deposits (750 cm) in the tract of Lake Peschanoe (Amur Region, between the Amur and Zeya rivers).

Material and methods. In the studied section, the composition of organomineral deposits were examined based on radiocarbon dating and palynological analysis.

Results. According to radiocarbon dating, the sedimentation began over 4 thousand calendar years. Specific features of the accumulation and distribution of rock-forming oxides and microelements along the organomineral sedimentary profile were established. The mineral composition is dominated by quartz, feldspars, amphiboles, pyrite, garnet and biotite. The highest values of the scattering coefficient in the thickness of the deposits are typical of Hg (8.0), Tl (6.7), La (5.3), below – Zr, Rb and Li (4.7, 4.4 and 4.1, respectively).

Conclusions. The study of the geochemical characteristics of organomineral deposits allowed us to identify the industrial period of sedimentation, which was characterized by an increase in the concentrations of Hg, Cd, Pb and Sn. The background contents of elements in the organomineral deposits of the Lake Peschanoe tract can be used as a regional background for deposits in the transboundary territory of the Upper and Middle Amur and its tributaries. The calculated geochemical coefficients indicate the freshwater content of the basin and the alternation of stagnant and oxidizing environments during sedimentation. The increased Ca/Sr values are associated with a change in the climatic regime towards cooling, which occurred during the last 4 thousand years in this area: 4300–4100, 2400–2100, 500–230 years ago.