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We report results of geostructural, mineralogical, petrographic, geochemical and geochronological (⁴⁰Ar/³⁹Ar) investigations of ophiolites from the northern and southeastern fragments of the Tatarka-Ishimba suture zone of the Yenisei Ridge combined into the Rybnaya-Panimba belt. The ophiolites consist of massive and pillow-lava metabasalt, massive and layered metagabbro and metadolerite, and represent fragments of the upper part of the oceanic crust. They formed in a mid-ocean ridge or marginal sea setting from depleted mantle sources corresponding to components of the N-MORB and E-MORB geochemical types. We propose a model for the tectonic history of emplacement of the ophiolites in the Meso-Neoproterozoic time. At the Meso-Neoproterozoic boundary (Stenian-Tonian), 1051-916 Ma, a thrust system was formed and the oceanic crust fragments (ophiolites) were accreted to the passive margin of the Central Angara terrane (microcontinent). The subsequent convergence and collision of this microcontinent with the Siberian Craton (786-749 Ma) caused the formation of strike-slip/thrust deformation in the rocks of the Tatarka-Ishimba suture zone including the ophiolites. In the Cryogenian time (708-700 Ma), strike-slip and reverse fault deformations occurred in these rocks due to a new episode of tectonic activity caused by the transition between convergent settings - end of the collision and start of the active continental margin.

We analyzed composition of monzonite-syenite intrusive rocks within the Bilikan-Khulamri magmatic zone of the central segment of the Yana-Kolyma Orogenic Belt. These rocks compose small intrusions cutting terrigenous strata of the Inyali-Debin turbidite terrane. The monzonitoids under consideration contain moderate amount of silica and Al₂O₃, relatively high contents of K₂O, Na₂O, MgO; by chemical composition they are similar to latite and very close to alkaline-salic intrusive rocks of the Aldan Igneous Province. Concentrations of major and rare elements indicate that these rocks belong to granitoids of convergent continental margins, including syncollisional and those of volcanic arcs. According to U-Pb dating (SIMS), the age of zircon from quartz syenite is 84.0 Ma. It corresponds to the secondary pulse of magmatic activity of the Okhotsk-Chukotka Volcanic Belt. The specific chemical composition of the monzonitoids close to the shoshonite-latite series is due to their location deep in the back arc of the volcanic belt, at more than 200 km from its axial zone, on the sialic bedrock composed by turbidite terrigenous complexes.

This paper deals with new geological, mineralogical, isotopic-geochemical (major, trace, and rare earth elements, Sm-Nd isotopic data) characteristics of the unique Kalevian (1926-1923 Ma) komatiite-tholeiitic magmatic manifestation for the first time identified in the supracrustal Kaskama Formation from the Inari terrane of the Kola-Norwegian region Fennoscandian Shield. In the massive and porphyritic komatiites, the primary (magmatic) mineral paragenesis represented by olivine 20-40%, orthopyroxene up to 5%, hornblende up to 10%, clinopyroxene 20-40% and plagioclase 20-30% was identified. Liquidus temperatures for olivine and pyroxenes calculated in the COMAGMAT3.73 software suite are in the range of ~ 1500-1200 °C. The komatiites of the Kaskama Formation belong to the Al-nondepleted type and are characterized by low REE _N content (1-2 relative to C1 chondrite), a total concentration ∑REE_avr = 0.15-0.36 ppm, and an unfractionated distribution of REEs, which is a consequence of the generation and evolution of their primary melts outside the field of thermodynamic conditions of garnet stability. The Zr-Y-Nb and Sm-Nd isotopic systematics of the rocks of the komatiite-tholeiitic association indicates the origin of their high-temperature primary melts from a plume source in depleted mantle (ε_Nd( T ) = +3.2 ± 0.3), which is different from the mantle sources of the Jatulian-Ludicovian picrite-komatiite association of the Central Lapland greenstone belt of Finland and the Pechenga intracratonic structure. Considering the amphibolite facies metamorphic conditions of the Kaskama Formation, it can be assumed that the komatiite-tholeiitic association is a deeply eroded (at least 10 km) section of a supracrustal volcan.

The metamorphic rocks in the northeastern Taimyr region are a consequential result of its complex geologic history. Series of metamorphic processes were associated with the formation of lode copper and noble-metal mineralization. The aim of this study is to investigate the type and degree of metamorphism of the host basic volcanic rocks in the ore cluster. We have identified three stages of metamorphic process: The first stage led to the formation of actinolite and sodium plagioclase paragenesis (with its chemical compositions corresponding to temperature of about 400 °C); the second stage resulted in the crystallization of hornblende, plagioclase, spessartine-almandine garnet, biotite, feldspars (oligoclase-andesine and K-Ba types), and various Fe-Ti phases (mineral geothermometers show the highest temperature range of 450-600 °C), and the final stage produced clinochlore, pyrite, and fluorapatite (330-290 °C according to the Al^IV contents in chlorite). We interpret the studied rocks as hornfels based on the highly discordant contours of the metamorphic aureole, the compositions of garnet (spessartine is a predominant component), and the K-Ar ages of biotite (253 ± 5 Ma) and plagioclase (239 ± 8 Ma), which coincide with the time of late Paleozoic-Mesozoic postcollisional granitoid magmatism. The absence of schistosity, the disequilibrium assemblages, and the abundance of volatile-rich minerals (containing F^-, OH^-, and SO₄^2-) also indicate their contact origin. The discovered aureole includes the known Cu-Au-Ag veins and metasomatic occurrences, the age of which is therefore late- or postmetamorphic. We confirm the earlier hypothesis of our colleagues about the impact of a concealed granite massif on the host rocks and consider the high metamorphic grade to be a natural boundary for the ore cluster.

The behavior of Ag in the oxidation zone of the Kyzyk-Chadr gold-sulfide-quartz deposit (Tuva Republic, Russia) is investigated. The primary focus is on the mechanisms of Ag differentiation under supergene conditions, including the formation of secondary minerals and silver incorporation as an isomorphic impurity into other phases. It was established that Ag in the oxidation zone forms chalcogenides (acanthite, petrovskaite, uytenbogaardtite, and jalpaite) and halides (iodargyrite, bromargyrite, and mayersite), which are associated with malachite, chrysocolla, brochantite, quartz, and iron hydroxides. Electron probe microanalysis reveals Ag concentrations in secondary copper sulfides (covellite, chalcocite, yarrowite, etc.) of ≤0.7 wt.%. Optimization of the microanalysis parameters to enhance resolution lowers the detection limit, enabling the determination of low Ag contents in chalcopyrite (≤0.05 wt.%) and bornite (≤0.09 wt.%). The sources of Ag are primary Ag tellurides and selenides, as well as primary and secondary Cu sulfides that decompose during the oxidation. Computer thermodynamic modeling is used to describe the behavior of Fe, Cu, and Ag during the progressive oxidation of primary assemblages (bornite, chalcopyrite, and acanthite). The Eh-pH conditions controlling mineral migration and reprecipitation are calculated, and the element concentrations required for the formation of secondary phases were estimated.

We report results on the age estimates of the Paleogene diatom datums derived from the magnetostratigraphy at the marine Cenozoic stratigraphic section of the Kvachina Bay, West Kamchatka. Based on a direct correlation with the Geomagnetic Polarity Time Scale, it was possible to determine the age of such levels in the interval between Subchron C13r (35.10-33.73 Ma) and Subchron C9r (27.86-27.44 Ma). Of greatest interest are the dates of the first and last occurrences of Lisitzinia ornata (27.71 Ma and 27.54 Ma respectively), and the first occurrence of Rocella gelida (27.49 Ma). This is the first experience of absolute age estimates of Oligocene diatom biohorizons based on magnetostratigraphy not only in Kamchatka sections, but in the North Pacific region in general. A comparison was made between the obtained age estimates and those published in the literature based on the study of deep-sea cores in various regions of the World Ocean.

We have estimated the proportion of sorbed water converted to ice and hydrate during the interaction of wet sand samples with methane by using the nuclear magnetic resonance (NMR) relaxometry method. There is a thin film of strongly bound water in small pores at the rock-fluid interface. This water does not freeze at the subzero temperatures achieved during the experiment; its amount remains constant without regard to the water content in a sample. We have calculated the amounts of strongly bound water and water converted to ice and hydrate for all samples. Based on the established hydrate stoichiometry, we have calculated the amount of methane converted to hydrate. Analysis of the obtained data has revealed the optimal water content in a sample, which results in the greatest amount of hydrate formation.

This study presents a comprehensive analysis of regional climate dynamics - specifically, solid precipitation - and its impact on mountain geosystems in the Kuznetsk Alatau. The research integrates long-term field observations with ERA5-Land reanalysis data, focusing on snowpack measurements across the Kanym Highlands (2011-2025). We detail the spatial distribution, parameters, and temporal variability of snow cover, including avalanche hazards and maximum snow redistribution volumes. Additionally, we provide new UAV-based monitoring results (2024) for the Iyus-Tersa glacier group, alongside a detailed assessment of six major glaciers’ retreat since the 1980s. The surface temperatures in the different landscapes (900-1500 m a.s.l.) were investigated. The well-documented snowpack dynamics of the Kanym Highlands and Iyus-Tersa glaciers enable a comparative analysis, shedding light on local geosystem responses to climate warming and associated physiographic changes. Our validation shows that while ERA5-Land reliably estimates ten-day mean snow depth at the foothills, it underestimates snowpack thickness in high-altitude cryosphere zones, underscoring the critical role of in situ measurements.

A key feature of the upper part of geological sections in the Arctic is the presence of permafrost, with which a number of cryogenic phenomena - thermokarst, frost mounds, gas-emission craters, etc. - are associated. These phenomena represent significant geohazards potentially causing large-scale negative consequences in the context of the actively developing oil and gas infrastructure. of the region. In this paper, some results from the interpretation of high-density shallow (up to 500 m) transient electromagnetic method data obtained in the eastern part of the Yamal Peninsula to identify fluid migration channels, which may be associated with the formation of frost mounds. It has been established that the distribution of frost mounds in the study area correlates with anomalies in polarizability and electrical resistivity. The layer of rocks, above which pingo-like landforms are found, is associated with the manifestation of inductively induced polarization likely characteristic of sediments with the low ice content, In the underlying strata, anomalies of reduced resistivity are noted, which may be associated with fluid migration channels and accumulations of gaseous hydrocarbons in the permafrost.

This article presents the results of a GPR study at groundwater discharge sites located in the Makhatta and Kysyl-Syr tukulans (Republic of Sakha (Yakutia)). GPR profiles were obtained using 50 and 150 MHz antenna systems, characterizing the structure of sandy sediments and the boundaries of suprapermafrost subaerial taliks. In the southeastern margin of the Makhatta Tukulan, groundwater boundaries with a depth of 4.5-10 m in different lithological conditions were identified. In the Kysyl-Syr Tukulan, watered horizons with a width of 550 m and a depth of 13-32 m forming complex channels of groundwater migration and discharge were detected.