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Sobolevite with low Mn content from the Karnasurt deposit (Lovozero, Kola peninsula) has been characterized by electron microprobe analysis, single-crystal structure refinement, high-temperature X-ray diffraction and density functional theory (DFT) calculations. The chemical formula can be written as Na_7.04(Ca_0.87Mg_0.16)_S=1.03(Ti_1.48Zr_0.20Mn²⁺_0.18 Nb_0.10Fe²⁺_0.06)_S=2.02Si_2.05P_2.02O_17.12F_0.88. The crystal structure refined to R₁ = 0.037 (P2₁/c, a = 7.0908(3), b = 5.4108(2), c = 40.6179(19) Å, b = 93.095(4)^o, V = 1556.11(11) ų) is based upon the [Ti₂O₂[Si₂O₇](PO₄)]^5- titanosilicate-phosphate HOH layers (TS blocks). The interlayer space is occupied by the AC complex formed by Na⁺, Ca²⁺ and Mg²⁺ cations along with (P1O₄)^3- groups and F^- anions. The F- anions are coordinated octahedrally by Na and Ca to form antiperovskite [FA₃] chains (A = Ca, Na) running parallel to the b axis. The crystal chemical formula of sobolevite is (Na_6.92Ca_0.92Mg_0.16)_S=2.00(Ti_1.46Zr_0.18Mn²⁺_0.15Nb_0.15Fe²⁺_0.06)_S=2.00(Si₂O₇)(PO₄)(F_0.81O_0.19)_S=1.00, which corresponds to the idealized formula Na₇CaTi₂O₂[Si₂O₇](PO₄)₂F and allows to consider it as a polymorph of quadruphite. The relations between sobolevite and quadruphite are pseudo-polytypic. The thermal behavior of sobolevite is typical for layered structures corrected by shear deformations. According to DFT calculations, sobolevite exhibits p-type semiconductor behavior with a band gap of approximately 2.75 eV. Altering the Ti/Nb ratio influences the band structure, inducing magnetism in the crystal and transforming it from a semiconductor to a semimetal or even a metal. The material exhibits strong absorption in the ultraviolet region, with an absorption coefficient reaching up to 2×10⁵ cm^-1. The overall structural architecture of sobolevite combines features of both titanosilicates and antiperovskite-type structures, which makes it an interesting example of hybrid structures with potentially interesting functional properties.

The article presents a methodology for quantitative verification of three-dimensional geoelectric models constructed from electrical tomography (ET) data in complex geological conditions. As an example of real data, a set of measurements is considered in the fault zone of the southeastern boundary of the Gorlovka depression (Novosibirsk region), where an increase in seismic activity has been observed in recent years. It is probably caused by the development of large coal mines. The relevance of the work is due to the interpretative ambiguity of ET data in heterogeneous geological environments and the appearance of artifacts in inversion models, which can subsequently lead to false interpretation of the results. It is proposed to move from the traditional visual comparison of the results of inversion of field and synthetic data to quantitative analysis. For this purpose, the ERT_Comp software tool has been developed, which calculates the relative difference between the model and field values ​​of apparent resistivity at specific spacings. The use of the technique for field data from three parallel profiles made it possible to quantitatively substantiate the choice of the optimal 3D geoelectric model reflecting the presence of a subvertical fault zone. The proposed approach does not completely remove ambiguity, but significantly increases the reliability of interpretation. Prospects for the work involve the use of gradient models and the establishment of standardized threshold values ​​of relative deviations to select the best interpretive model.

The Romanche Fracture Zone plays a crucial role in the distribution of Antarctic Bottom Water between the western and eastern Atlantic. However, the influence of bottom currents and other processes on the sediment infilling of the Romanche valley remains understudied. A large set of high-resolution sub-bottom profiling data was used in this work to solve this issue. The interpretation of the results was supported by numerical modeling of bottom current velocities using an ocean circulation model. The first comprehensive map of echo character distribution along the entire transform valley was built, revealing detailed sediment distribution patterns. The study assessed the modern and past influence of bottom currents on sedimentation and identified areas of intense gravity flow activity. The results highlight the Romanche valley as a promising area for studying the history of water exchange between the western and eastern Atlantic.

Profitability, efficiency, and safety in the
coal mining industry depend on the mining and geological conditions. Quite
often, the geological forecast is not confirmed, especially in the presence of
small-amplitude tectonic disturbances and local geological inhomogeneities,
which is why the development and application of geophysical methods, including
various types of seismic exploration, is of great importance. The article
presents the results of ground-based seismic surveys at the Chulmakan coal
deposit in the Sakha Republic (Yakutia) to clarify the general geological
structure of the study area, identify thin coal layers, study their structure,
and detect tectonic faults. It has been shown that, due to fundamental physical
and technological limitations, the reflected wave method cannot be the only
source of reliable information when studying fine-structured objects. Based on
the joint interpretation of reflected and refracted waves, as well as the
analysis of well data, the authors have successfully traced and refined the
parameters of the thin coal layers, and identified several tectonic faults that
were not detected by drilling. It is also shown that the purposeful development
of methodology, technical means, and technologies for interpreting refracted
waves is not just an academic interest, but an urgent production necessity.

We obtained the experimental and theoretical data on the temperature and pressure dependencies of the viscosity of model ultramafic and basalt melts at mantle thermodynamic parameters. Based on systematic experimental and theoretical studies, we established generalized patterns of the temperature and pressure dependencies of the viscosity of depolymerized magmatic melts (basaltic, model ultramafic and kimberlite) under conditions of the upper mantle. We have established an anomalous and extreme dependence of the viscosity of basaltic melts on pressure: as the pressure increases, the viscosity of such melts decreases, passes through a minimum, and then increases again. In contrast, for depolymerized ultramafic melts, the dependence of their viscosity on pressure corresponds to the theoretical dependence, i.e., as the pressure increases, the viscosity of such melts increases exponentially. A structural - chemical model has been developed for reliable predictions and calculations of the viscosity of magmatic melts in the full range of their basicity, from acidic to ultramafic, at T, P - parameters of the Earth's crust and upper mantle, with an error comparable to the experimental error. Using a computer version of this model, the characteristic features of the change in viscosity of ultramafic and basalt melts as they rise from the mantle to the Earth's crust have been established.

An approach is proposed for assessing the distribution of industrial minerals in the upper part of the geological section based on reprocessing and interpretation of archived 3D seismic data. The approach includes reconstruction of P- and S-wave velocity models using modified refraction and surface wave methods, automated extraction of dispersion curves using a neural network algorithm, as well as calculation and integration of a set of seismic and morphometric attributes. Based on the combined feature space, clustering is performed to delineate facies associated with deposits of different genesis. The approach was tested on the Kharampur license area located in the Arctic zone of West Siberia, characterized by the presence of permafrost. For this site (area ~60 km²), it is shown that the proposed workflow enables the construction of detailed predictive maps consistent with drilling data and active quarries. Clustering based on combined seismic and terrain-related features allowed identification of facies and the construction of physico-geological models of sand and peat bodies with economically significant thicknesses. This approach enables the generation of high-resolution predictive maps without additional field surveys, with a resolution comparable to engineering-scale drilling data.

This paper presents the results of studies of zircon grains from kimberlite and carbonatite bodies, as well as from ancient and modern diamond placers of the Lena–Anabar subprovince of the Siberian Diamond Province. The research includes U–Pb zircon dating and the determination of trace and rare earth element concentrations using the SHRIMP-IIe secondary ion mass spectrometer. The study covered kimberlite primary bodies of different ages, Late Jurassic carbonatite breccias, all diamond placers of the Anabar, Kuonamka, and Prilensky regions, as well as placer occurrences in the Primorsky, Lower Olenek, Middle Olenek, Muno-Tyung, and Daldyn-Alakit diamondiferous regions. In association with diamonds, zircon grains yielded Jurassic, Triassic, Permian, Late Devonian-Early Carboniferous, and Silurian-Early Devonian ages, which are consistent with the ages of known primary sources. New data indicate a broader age range of Triassic productive volcanism. Analysis of all diamond placers showed that approximately 79% of them were formed from Triassic primary sources.

The article presents the results obtained during the crystallization of a melt with the compositionin (in at. %): 14.0 Cu, 30.0 Fe, 4.0 Ni, 51.1 S, 0.1 each of Pt, Pd, Ag, Au, As, Bi, Pb, Se and Sn, in wt. %: 19.5 Cu, 36.7 Fe, 5.1 Ni, 35.8 S, 0.4 Pt, 0.2 Pd, 0.2 Ag, 0.4 Au, 0.2 As,0.5 Bi, 0.5 Pb, 0.2 Se and 0.3 Sn under isothermal conditions and with directional crystallization. Under gradient-free conditions, a homogeneous crystalline massif consisting of a mixture of monosulfide and intermediate solid solutions crystallizes from the melt. When cooled to room temperature, the monosulfide solid solution forms the pyrrhotite structure 1C, 3C, and the intermediate solid solution decomposes into a fine-grained mixture of isocubanite and chalcopyrite. Using the Bridgman-Stockbarger method, a three-zone ingot was obtained with the following sequence of phase crystallization from the melt: Mss / Iss₁ / Iss₂ and secondary zoning: chalcopyrite + pyrrhotite 1C, 3C + isocubanite (zone I) / chalcopyrite + low-temperature intermediate solid solution + Fe-pentlandite, sugakiite (zone II) / chalcopyrite + Ni-pentlandite + millerite + bornite (zone III). The specific influence of As, Bi, Pb, Se and Sn impurities on the behavior of Pt, Pd, Ag and Au under different crystallization conditions was revealed. In both experiments, solid solutions play a minor role in their concentration. The main amount of these impurities is released in the form of independent phases. The main role in their formation is played of immiscibility of the parent sulfide melt, resulting in the formation of a sulfide-metalloid melt, L_s-m, which concentrates impurities of Pt, Pd, Ag, Au, and chalcophile elements. The data on the directionally crystallized sample indicate a more complex process of immiscibility of the initial melt compared to its immiscibility during volumetric crystallization, namely 1) the simultaneous release of two types of liquids during cooling of the initial sulfide melt in zone II: one of these liquids is formed in the (Pd, Au)-(As, Bi) subsystem, and the second in the (Pt, Pd)-Pb-(S, Bi, As) subsystem; 2) in zone III, secondary immiscibility and phase formation processes may occur within the L_s-m droplets during cooling; 3) сoncentration of microphases at the end of the ingot in zone III.

As a result of data processing for more than 3000 clinopyroxene xenocrysts from kimberlites of different ages in the Siberian Platform, a generalized model of the lithospheric mantle thickness evolution within the Yakutian diamond province has been obtained. New data on surface heat flow (SHF) and thermal lithospheric thickness (TLT) have been obtained for seven localities on the Siberian Platform, including Paleozoic and Mesozoic kimberlites from different regions with different diamond potential, as well as Late Triassic sedimentary rocks from the northeastern margin of the platform. The composition of clinopyroxenes from the Late Triassic sedimentary rocks corresponds to the Devonian–Carboniferous type of lithospheric mantle of the Siberian Platform. New data on kimberlites from the northeastern part of the platform (Ivushka and Zaoblachnaya pipes) yield results that contradict previous interpretations. The Ivushka pipe (Toluopka field) exhibits a TLT thickness closer to that of Jurassic kimberlites, but the sampling depth of clinopyroxene-bearing rocks is typical of Devonian–Carboniferous kimberlites. The geotherm of the Zaoblachnaya pipe (Khorbusuon field) corresponds to Devonian–Carboniferous and Triassic kimberlites, which contradicts the absence of diamonds in the pipe and its tectonic setting. The SHF and TLT values separating the Jurassic lithosphere of the northeastern part of the platform from the older lithosphere are 36.9 mW/m² and 230 km, respectively. Based on the TLT and the depth of lithospheric section sampled by kimberlite magmas of different ages, it is shown that the lower diamond potential of Triassic kimberlites may be related not to lithospheric thinning, but to a shallower depth of onset of mantle material entrainment, caused by increased permeability of the lithospheric mantle resulting from the preceding influence of the Permo–Triassic plume.

This paper presents an analysis of compositional data on Proterozoic dolerites from dikes and sills on the southern flank of the Siberian Craton, formed in an intracontinental setting between 1.91 and 0.72 Ga. Indicator geochemical parameters have been established for four age groups of dolerites, reflecting differences in their of mantle sources and the conditions of generation of the initial melts. Neoproterozoic dolerites of the Nersa complex are characterized by lowest (Sm/Yb)_n and (Nb/Y)_pm ratios and were formed with the contribution from enriched subduction-modified lithospheric mantle (SZLM) and a depleted (asthenospheric) source. Dolerites aged 1.35 Ga are distinguished by the maximum concentrations of incompatible rare elements and high (Sm/Yb)_n and (Nb/Y)_pm values, their formation occurred from an enriched plume mantle source. Mesoproterozoic (~1.6 Ga) dolerites of the Prisayan Trough are characterized by elevated contents of TiO₂ and high-field strength (Nb, Ta) elements compared to dolerites of the Nersa Complex. They are dominated by an enriched plume source with high (Nb/Y)_pm and TiO₂/Yb ratios, with limited contribution from SZLM. Paleoproterozoic (1.91 Ga) dolerites, while similar in (Sm/Yb)_n values to Neoproterozoic ones, have lower (Nb/Y)_pm and (Nb/La)_pm ratios, indicating a more depleted mantle source. The proposed diagrams (Sm/Yb)_n – (Nb/Y)_pm and (Nb/La)_pm – (Nb/Y)_pm allow us to systematize dolerites from the dike swarms of the southern flank of the Siberian craton based on the similarity in composition with dolerites of four stages of Proterozoic basic magmatism.