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We present data on the finds of glendonites (pseudomorphs after cold-water ikaite) in Permian, Jurassic, and Lower Cretaceous sedimentary rocks according to the drilling results of borehole KS-1, located on the coast of the Laptev Sea. This is the only section in the world that contains both Paleozoic and Mesozoic glendonites corresponding to three geological systems. We have found glendonites at all previously known stratigraphic levels in northern Siberia, excluding intervals with relatively rare glendonite finds (Oxfordian, Ryazanian, and Valanginian stages). There are the most numerous, diverse, and large glendonites in the Middle Jurassic interval of the section (Bajocian-Callovian). The KS-1 borehole is a unique natural archive that reflects significant late Paleozoic-Mesozoic events of cooling in the region under study.

We present the first reconstruction of a lacustrine sedimentary environment for the extensive area of the Angara steppe (Baikal peripheral basin) in the late Holocene with decadal temporal resolution. The reconstruction is based on the results of a comprehensive study of lacustrine sediments from Lake Ordynskoe: petromagnetic and granulometric parameters and biogenic silica content. We have determined sedimentation rates and the age of the reconstructed events using radioisotope dating (²¹⁰Pb and ¹³⁷Cs). The age of the core base is 2800 cal yr BP. The results show that the primary contribution to the magnetization of sediments from Lake Ordynskoe, unlike other studied lakes in the region, comes from grains produced by magnetotactic bacteria. However, the behavior analysis of biogenic components of magnetization provides information on the lake bioproductivity and relative changes in redox conditions during the formation of sediments at the water-sediment interface, and the results of granulometry are informative for reconstructing relative changes in the lake level. Despite this particularity in the formation of the lake’s petromagnetic sediments, we have established that noticeable anthropogenic impact on the geosystem of Lake Ordynskoe began approximately 280 years ago, significantly increasing in the last century due to agricultural activity.

This paper describes a system for monitoring the seismicity of specific volcanic regions in Kamchatka (Russia, Kamchatka Peninsula) with an assessment of the seismicity level according to the SESL’09 (Statistical Estimation of Seismicity Level) methodology. The application of the SESL’09 methodology for the purpose of investigating the preparation of volcanic activations is a promising direction in conducting volcano status monitoring. We present the results of identifying seismically active source volumes for 10 active volcanoes in Kamchatka, for which nomograms have been constructed that allow for the estimation of the seismicity level for any given time interval based on the seismic energy released within it. Examples of variations in the seismicity level of these volcanic regions associated with the preparation of an eruption are provided, confirming this conclusion.

The article presents algorithms for numerical modeling of electrical micrologging signals and calculation results in geoelectric models of impermeable rocks and the borehole environment of a porous, permeable reservoir. This research may be useful for developing an integrated approach to the quantitative interpretation of electrical logging data. A joint numerical analysis of electrical logs measured by conventional probes and microprobes will enable refining the radial electrical resistivity distribution in the borehole environment of oil-gas reservoirs. This, in turn, will provide additional information when jointly solving the problem of drilling mud filtration and numerical inversion of electrical logging data, resulting in a more accurate assessment of reservoir porosity and permeability. We have developed software for numerical simulation of electrical micrologging signals - those from a microgradient and micropotential probe and a microlaterolog probe with focusing. We employ a finite element (FEM) algorithm with an arbitrary position of the probes in a cylindrically-layered geoelectric model, and a finite difference (FDM) algorithm for the microgradient and micropotential probe in a horizontally-layered model. Test calculations of the signals in geoelectric models of Western Siberian terrigenous deposits are presented. The models describe impermeable sediments as well as layers with the mud cake and invaded zone at different resistivity ratios. The model parameters correspond to Lower Cretaceous oil-gas reservoirs exposed with polymer-clay drilling muds. An analysis of the calculated micrologging signals reflects a small investigation depth of the microgradient and micropotential probe, and a strong dependence of the signals on the drilling mud and mud cake resistivities. Numerical modeling in the class of a cylindrically-layered model has allowed us to obtain the radial resistivity change in the borehole environment of an oil-gas reservoir.

A detailed study of an alkali beryl sample (vorobyevite) from the Shuk-Bul rare-metal lithium pegmatite (Sangilen Highlands, Tuva) was conducted using electron microprobe and ion probe(SIMS) analysis, X-ray diffraction, EPR spectroscopy, infrared absorption spectroscopy, Raman spectroscopy. The empirical formula of beryl studied was calculated: (Na_0.2Cs_0.1)_∑0.3(Be_2.7Li_0.3)_∑3.0Al₂Si₆O₁₈·0.7H₂O. The ratio of water types I and II in beryl channels is estimated. Beryl from the Shuk-Bul deposit shows significant similarity in trace element composition with beryl from another lithium pegmatite deposit of the Sangilen Highlands (Kara-Adyr). Together, they differ from beryl from LCT-pegmatites of Afghanistan and the Kola Peninsula (the Shongui deposit) in their increased content of alkali metals - Cs and Rb, as well as F, and reduced – Fe and Mg. The content of Na and Li in beryl from Tuva deposits is comparable to the Shongui deposit and exceeds the values for beryl from LCT-pegmatites of Afghanistan. The presence of paramagnetic centers H⁰ in beryl, formed from water molecules under the influence of radioactive irradiation, has been established. Using a Calvet microcalorimeter, the enthalpy of formation of the studied beryl was determined (−9245 ±11 kJ/mol) by dissolving it in a 2PbO∙B₂O₃ melt at T=973 K, the standard entropy was estimated (390.7J/(mol∙K)), and the Gibbs energy of formation was calculated (−8696 ±11 kJ/mol).

This paper presents new isotope-geochronological, rock magnetic and paleomagnetic data for the Berezinovsky and Tayandinsky Early Carboniferous volcanic complexes of the East Ural zone of the Southern Urals. The cover nature of the basalts is demonstrated, lava flow patterns and their directions are identified, and the strikes of the subvolcanic bodies are clarified. Using the LA-Q-ICP-MS laser ablation method, an age of 339.0 ± 1.0 Ma was obtained for rhyolites of the Berezinovsky complex. It is shown that by this time, the East Ural zone had already accreted to the East European Platform and formed a single structure with it.

An analysis of oil and gas potential prerequisites forms the basis of a zonal forecast strategy for oil and gas-promising areas and ensures rational subsoil use. The relevance of the study stems from the need to replenish the hydrocarbon resource base by discovering new large gas accumulation zones. The oil and gas potential of the Upper Paleozoic-Mesozoic deposits of the Vilyui hemisyneclise was predominantly influenced by the post-Jurassic stage of tectonic development, which is associated with the formation of the main structures—oil and gas accumulation zones—and faults capable of acting as channels for hydrocarbon migration from the Permian source strata to Upper Permian, Lower Triassic, and Lower Jurassic reservoirs. The distribution patterns of hydrocarbon deposits in the largely sandy section of the Mesozoic sedimentary cover of the Vilyui hemisyneclise are largely determined by the stratigraphic and areal distribution of seal rocks, which controls the main gas reserves.

This paper examines the geological setting of the two strongest earthquakes recorded in the Altai-Sayan mountainous region in 2025: the Beltirskoe earthquake (ML=6.4) and the Kuraiskoe earthquake (ML=5.7), which occurred on opposite margins of the Chagan-Uzun block. Data on the aftershock sequences of these earthquakes are presented. The analysis demonstrates that these earthquakes occurred in the vicinity of, yet outside, the source region of the 2003 Chuia earthquake. The 2025 events were studied with reference to available data on the aftershock activity of the Chuia earthquake. It is shown that the Chuia earthquake is associated with the shear zone of the eponymous fault and encompasses a linear area along one of the margins of the Chagan-Uzun block. During the main shock, the block itself was incorporated into the source region in the form of weak earthquakes occurring beneath it at depths of 10–20 km (a seismically active layer adjacent to the Chuia earthquake source zone). The focal mechanisms of the Beltirskoe and Kuraiskoe earthquakes are thrust-type, whereas the mechanisms of all strong aftershocks of the Chuia earthquake are strike-slip. Both 2025 earthquakes generated aftershock sequences of low intensity. The hypocenters of the main events and the majority of aftershocks are located at shallow depths, with a maximum concentration at approximately 3–5 km. The 2025 earthquakes represent a continuation of seismic activity in the Altai region within the near-field zone of the Chuia earthquake, reflecting a delayed temporal response of crustal blocks that experienced alterations in their stress state following the impact of a major seismic event.

This paper presents the results of a study conducted on the chemical composition of ores from the Marinskoye orogenic gold ore field, located in the Allakh-Yun metallogenic zone of the Okhotsk-Koryak metallogenic belt (South Verkhoyanye). The deposit developed in a suprasubduction setting over the course of three discrete stages of ore formation: the early-ore stage (the Tithonian of the Late Cretaceous), the late-ore stage (the Aptian of the Early Cretaceous), which was associated with the exhumation of early ore-bearing complexes, and the telescoping of the late mineralization into early and post-ore stages. The main ore-bearing vein mineral is quartz; less common minerals include Fe-dolomite, dolomite and sericite. Ore minerals: primary – pyrite; secondary – arsenopyrite, galena, sphalerite; rare – native gold, pyrrhotite, boulangerite, hessite, petzite, sylvanite, tsnigriite, chalcopyrite, electrum, tetrahedrite, freieslebenite, diaphorite, stephanite. Ores from the early ore-forming stage are composed of quartz–sericite–carbonate–pyrite, arsenopyrite–pyrite–quartz, gold–galena–carbonate and telluride–sulphotelluride–sulfosalt associations; the total sulphide content in the ores is 1-2%. The metasomatites contain sparse inclusions of cubic crystals of arsenic-bearing gold-bearing pyrite (C_{As mean} = 1.17±0.06 wt%, С_{Au mean} = 3.4±0.3 g/t). The early vein association consists of quartz with significant impurities of Ni (up to 61 g/t) and Cd (up to 4.3 g/t) and a low content of REE (SREE = 0.5-1.2 g/t). The fineness of native gold ranges from 660 to 780‰. Hessite, silvanite and tsnigriitehave been described for the first time at the Marinskoye deposit. In ores from the late-ore stage of mineralization, quartz–pyrite, pyrite–quartz, gold–polysulfide–carbonate, and Ag–sulfosalt associations have been identified, with sulfide content increasing to 5%. Low-arsenic pyrite with a pentagonal-dodecahedral shape is characteristic of the wallrock and quartz-carbonate veins. REE concentrations in quartz reach 29.6 g/t, their distribution shows enrichment in light lanthanides (LREE/HREE = 13.4-13.8), and a low-amplitude positive Eu-anomaly (Eu/Eu* = 1.3-1.6). In grains and aggregates of low-grade gold (up to 600‰), electrum rims and veinlets are prominent. The post-ore stage of mineral formation consists of minerals belonging to the quartz-carbonate association. The established general and distinctive properties of the mineralogical and geochemical composition of the ores of a different age at the Marinskoye deposit are essential for evaluating metallogenic potential of the telescoped ores.

Monitoring tasks often require the installation of temporary or local densification of existing seismic networks. The high cost of standard broadband seismometers limits the possibilities of increasing the number of stations. An alternative is to replace them completely or partially with more low-cost seismic exploration geophones with the expansion of the recording frequency range by low-frequency deconvolution. A methodology is proposed for assessing the applicability of geophone-recorder equipment sets for seismological monitoring tasks based on measurements of the recorder's hardware noise and the passport characteristics of the geophone sensor. It is shown that only the use of modern low-noise recorders and low-frequency geophones provides sufficient sensitivity for monitoring local and regional seismicity. A new method has also been proposed for determining the maximum allowable value for frequency correction of recording a specific earthquake (for this, the amplitude-frequency response of recording the recorder's hardware noise and recording after deconvolution are iteratively compared). It turns out that the more intense the earthquake, the more effective is the expansion of its recording spectrum. Using the example of recording the Kolyvan earthquake (M =4.3, epicentral distance of 30 km), the possibility of restoring the recording spectrum to 0.3 Hz for a geophone with a natural frequency of 4.5 Hz is shown. Due to this, the signal amplitude increased by more than 3 times, and the process of identifying phases and determining the arrival times of target waves was significantly simplified. It is shown how, using the seismic mode at the location of the proposed network installation, it is possible to assess whether the earthquake records produced by the proposed kit will be distorted and to determine its applicability in advance. The method has been tested using the example of equipment selection and data processing of a temporary seismological network in the Lena River delta.