This study presents an inaugural analysis of rock-forming mineral chemistry within andesites from the Polovinkinskaya Depression, situated at the junction of the Tynda and Nimnyr terranes in the central Aldan- Stanovoy Shield. Utilizing microprobe data processed through MagMin PT, WinPyrox, and COMAGMAT, we evaluated the systematics, thermodynamic crystallization conditions, and potential metallogenic significance of these rocks. The mineral assemblage includes plagioclase (oligoclase and two generations of andesine), groundmass andesine microlites, pyroxenes (augite and diopside), Ca-amphiboles (edenite and pargasite), and Mg-biotite. Our findings indicate that plagioclase crystallization occurred under conditions analogous to those found in island arcs and active continental margins, characterized by high oxygen fugacity (logfO₂=-5.04 to -6.86), temperatures ranging from 1090°C to 1124°C, and pressures decreasing from 12 to 4,5 kbar. These data support the hypothesis that subducted oceanic crust from the Mongol-Okhotsk Basin contributed to the Mesozoic Aldan magmatic sources. Furthermore, the identified P-T depth intervals (36–24, 24–12, 12–6, and 6–2 km) suggest the presence of intermediate Mesozoic magma chambers. Finally, an assessment of amphibole and biotite typomorphism, combined with the geological evolution of the andesites, indicates a high potential for epithermal gold mineralization in the region.

The article presents the results of systematization and analysis of archival geological materials on the Khokhsolakh gold-antimony zone (Sette-Daban, Yakutia) in order to clarify the geological and structural conditions of ore localization and assess its metallogenic potential. It was established that the Khokhsolakh occurrence is confined to a crush zone in the core of a gently dipping brachyform anticline, composed of Lower Carboniferous terrigenous rocks (Khatynakh C₁h and Natalka C₁n formations), and is spatially confined to the zone of influence of the regional Taskan fault. Based on the analysis of archival materials, the characteristics of two ore bodies, represented by quartz-stibnite breccias with gold grades up to 42 g/t and antimony up to 29 %, were detailed. Using materials from the State Geological Map-1000/3, a quantitative assessment of forecast resources was carried out, confirming the presence of 10 tons of gold and 15 thousand tons of antimony of the P₂ category. A critical analysis of the prospecting methods of past years (low-sensitivity geochemistry, fragmentary geophysics) revealed the reasons for the incomplete assessment of the zone’s potential. Based on the program of a new stage of geological re-study (GRD-200, 2025–2027), a modern predictive prospecting complex was substantiated, including ICP-MS lithochemistry, ground geophysical surveys, and isotope-geochronological studies. The conclusion was drawn about the high industrial potential of the Khokhsolakh zone and the feasibility of its designation as a priority prospecting area.

This article presents the results of a long-term study of the combined effects of suffusion processes on the development of soil erosion in agricultural landscapes. The primary objective of this study is to analyze the role of suffusion-subsidence processes in the development of soil erosion from snowmelt runoff and the transformation of the microrelief of arable land in the southeast of the Tomsk region. The materials used are the results of route surveys of arable land in the southern regions of the region over a period of thirty years, as well as semi-permanent observations at key sites “10 km” (2003–2014) and “Luchanovo” (1988–2026). Cartographic and granulometric methods, as well as the interpretation of satellite images and geographic information systems (GIS), were used in the analysis. As a result, three types of influence of suffusion processes on meltwater erosion were identified: soil loss from depression slopes to their bottoms, meltwater overflow from one depression to another located hypsometrically lower, transporting lithomas, and water breaking through the sides of basins into adjacent cropland. Modern manifestations of external suffusion were recorded, including soil subsidence on the slopes of agricultural landscapes and the reactivation of buried gullies. The obtained data on the scale of solid material movement will help refine existing methods for calculating soil loss and develop anti-erosion measures to protect cropland in the southeastern Tomsk region. The identified role of depressions as geochemical barriers opens up new opportunities for studying nutrient migration in agricultural landscapes.

This article presents the results of hydrobiological monitoring of phytoplankton in Avacha Bay (Southeastern Kamchatka), conducted in April, May, and July 2025. The study material comprised 19 samples collected at three stations from the surface and bottom water layers. Sample processing was performed using light microscopy with a Sedgwick–Rafter counting chamber for quantitative cell enumeration. During the laboratory analysis, 51 taxa of microalgae were identified, among which diatoms constituted the dominant group in terms of species diversity (35 taxa). A clear seasonal succession of the dominant complex was established: in April–May, absolute predominance belonged to the diatoms Detonula confervacea (Cleve) Gran, Thalassiosira nordenskoldii Cleve, and Skeletonema spp., whereas in July, a monodominant bloom of the potentially toxic dinoflagellate Alexandrium tamarense (Lebour) Balech was recorded in the surface horizon, with a maximum abundance of 15.9 million cells/L, accompanied by neon bioluminescence. Significant differences in quantitative parameters between the surface and bottom horizons were revealed: in May, Skeletonema spp. reached maximum concentrations in the bottom layer (up to 7.7 million cells/L), while in July, the dominance of A. tamarense was characteristic exclusively of the surface layer, which is likely associated with differences in temperature, illumination, and nutrient content at different depths. An inverse gradient of toxic species concentration from the eutrophied inner part of the water area toward the mouth of the bay was established, which may indicate heterogeneity of hydrological and trophic conditions within the studied water area.

The high dynamism of phytoplankton in Avacha Bay necessitates enhanced monitoring of toxic dinoflagellates of the genus Alexandrium, due to their potential danger to marine organisms and humans. Regular observations will enable the prediction of bloom risks in recreationally significant areas of Kamchatka.

Objective of the study – a comparative analysis of the seasonal dynamics and structure of phytoplankton in the surface and bottom layers of Avacha Bay during spring–summer 2025.

In recent years, cryogenic processes have been actively intensifying across the Sakha Republic (Yakutia), particularly in disturbed landscapes as a consequence of modern climate warming, evidenced by the rise in mean annual air temperatures since the late 1980s. The intensification of cryogenic processes affects the population’s quality of life primarily the stability of engineering structures and the environmental risks associated with potential accidents. South Yakutia lies within a zone of discontinuous permafrost, where numerous industrial facilities are concentrated. This article examines the results of predictive modeling regarding the geocryological conditions of South Yakutia under scenarios of climate warming and vegetation cover disturbance, specifically due to catastrophic fires and logging in mountainous taiga and sparse-forest areas. The study focuses on the active layer thickness and permafrost temperature within typical South Yakutia landscapes, specifically on sites underlain by loamy deluvium on gentle slopes and by stony-rubbly deposits on flat upland areas. Predictive modeling conducted for a 20-year period covering the Upper Amga, Tommot, and Chulman sites, taking into account current trends of rising mean annual air temperatures. Predictive modeling indicates that a combination of factors an increase in mean annual air temperature of 0.02°C per year and the loss of vegetation cover will cause the upper layer of permafrost to thaw to a depth of 5–9 meters and ground temperatures to rise by 1.2°C, thereby triggering subsidence and landslide processes. Calculations suggest that maximum thaw depths will occur in the rocky soils of slopes and plateau areas, a phenomenon attributed to their thermophysical properties.

Circulation factors determine forest fire risk and the likelihood of catastrophic flooding in northern Siberia and the Russian Far East. In this study, summer cyclonic activity over the Sakha Republic (Yakutia) is quantified using cyclone track data obtained from the ERA5 reanalysis model. The assessment utilized the number of cyclones and their centers, the density of cyclone centers and trajectories, and the cyclone coverage of the territory (the number of instances during the summer when a given point was within a low-pressure area). The main center of cyclonic activity is northeastern Yakutia (the upper Yana and Indigirka river basins, as well as the middle and lower reaches of the Kolyma River), where the highest density of cyclone tracks and centers is observed. Our results support the persistence of Verkhoyansk zone of local orographic cyclogenesis. Northwestern Yakutia (the Anabar and Olenyok river basins, the left-bank part of the upper Vilyuy River basin), due to baric formations shifting across the northwest of Krasnoyarsk Krai, has the highest cyclone coverage. Summer cyclonic activity is lowest in the southern regions of Yakutia; this is also the only region where July, rather than June, cyclones are most active. June cyclones dominate the total summer cyclone count in most years; however, July cyclones have become predominant since 2014. The number of summer cyclones has consistently increased by 0.64 cyclones over the 10-year period (1950-2017). In 2019-2020, the region experienced a historical minimum in cyclonic activity, making this trend statistically insignificant. This minimum chronologically coincides with other extreme events: floods in the Far East and the Irkutsk Region, low water levels in the middle reaches of the Lena River (2019), and severe forest fires in Yakutia (2019-2021).

The gross and particle size distribution (PSD) of parent materials is a fundamental characteristic determining genesis, physical, chemical properties, and ecological status of permafrost. Systematic comparative studies across the latitudinal belt remain extremely limited in Yakutia. The aim of this study was to analyze the gross and PSD of parent materials in three different landscapes: Spasskaya Pad (Central Yakutia), Elgeeii (Southeastern Yakutia), and Chokurdakh tundra site (Northeastern Yakutia). The methods of PSD and X-ray fluorescence analyzes of gross chemical composition were methodological basis. It has been established that the soil-forming rocks change in series from sandy loam alluvial deposits of tundra with of 0.05–0.01 mm fraction (Chokurdakh) through sandy-loamy carbonate deposits of Ice complex (Spasskaya Pad) to homogeneous eluvial- deluvial loams with maximum content of physical clay (Elgeeii). The gross chemical composition reflects quartz- feldspar mineralogical profile, with Spasskaya Pad rocks being characterized by carbonate content with high CaO (up to 20.03 %) and Sr (up to 519 μg/g) contents; Elgeeii rocks by elevated Fe₂O₃ (up to 6.10 %) and TiO₂ (up to 0.91 %) concentrations; and Chokurdakh by maximum Zr content (up to 656 μg/g), which is associated with the presence of accessory minerals in alluvial deposits. The identified differences correlate with cryogenesis, the thickness of the seasonally thawed layer (from 24 to 106 cm), organic carbon content (from 1.15 to 46.8 %), and the soil type. The results substantiate the need for an approach to assessing soil resources, modeling carbon pools and can serve as a basis for improving regional classification systems.