The article discusses possible mechanisms for the formation of ikaite (CaCO3·6H2O) in the sediments of the Kara Sea. We combined our own data with the results of previous studies on calcium carbonate hexahydrates in this region. X-ray diffraction analysis of ikaite revealed its transformation into calcite, providing valuable insight into its mineralogical evolution. Stable isotope analyses suggest that the main process leading to ikaite formation is microbial degradation of organic matter through sulfate reduction, which increases the concentration of dissolved inorganic carbon and phosphate ions in the pore water. Carbon that enters the bicarbonate ion as a result of anaerobic oxidation of methane (AOM) can also contribute to the formation of ikaite in some cases. However, AOM alone does not lead to the release of magnesium or phosphate ions, which are known to inhibit calcite precipitation. Consequently, without the simultaneous microbial decomposition of organic matter or the presence of unstable magnesium-rich minerals, AOM alone is not sufficient for ikaite formation. Our sample analyses show that the proportion of methane-derived carbon in ikaite does not exceed 62%, while the contribution of organic carbon can be as high as 100%. Furthermore, rare earth element (REE) analysis supports the significant role of diagenetic organic matter degradation in sediments where ikaite is present. These findings highlight the complex relationship between the decomposition of organic matter, the oxidation of methane, and the formation of ikaite in the early diagenetic sediments of the Kara Sea.

Vertical distribution of macrobenthos in sediments remains poorly studied; data from higher latitudes are especially scarce. At the same time, it is believed to contain important information about communities that should not be neglected. Hence, our main objectives are to study the peculiarities of macrobenthos vertical patterns in the Arctic and to find out features specific to this region. For this, 24 stations were sampled in 2019 aboard the R/V “Akademik Tryoshnikov” while drifting in the North Barents Sea and along a transect south-west of the Franz Joseph Land. Sediments were obtained using a box corer; afterwards, subsamples were taken by a tube corer and cut into vertical sub-cores. Three to four strata (depending on biotope) characterized by similar species composition and abundance were distinguished. No direct relation between the increase in species richness and the complication of vertical structure was found. Avoiding competition through dwelling in different layers at one station was observed in some groups of closely related species. Factors playing important roles in determining infaunal properties depended on the layer. The thin upper layer played a more important role in terms of species number and abundance as compared to lower latitudes. However, the most abundant and widespread polychaete species Spiochaetopterus typicus penetrated down to 30 cm. It formed vertical distribution patterns in deeper sediment layers at most stations, including facilitating penetration into deep layers for other species. The exception was stations dominated by large maldanid polychaetes. Such a vertical pattern, with a particularly large share of species richness and abundance concentrated in the several upper cm combined with the very deep penetration of a few species, is likely typical of the Eurasian Arctic shelf.

The present work is devoted to studying the characteristics of the spatiotemporal microearthquake distribution in the Lena Delta using data from local seismological monitoring conducted from 2016 to 2018. The results revealed the confinement of microearthquake sources to the Olenek segment of the Lena–Taimyr zone of boundary uplifts, marking the boundary of the Siberian Platform and the Laptev Sea Rift System. The Olenek segment fault zone is traced by hypocenters up to the Moho at a depth of about 40 km. Microearthquakes are distributed unevenly in both space and time, forming clusters in different parts of the fault zone. These clusters can be interpreted as originating from unstable stick-slip sliding during the process of background stable creeping. Seasonal variability in the number of recorded weak earthquakes in the Lena Delta has been revealed. An extended regional catalog (2003–2022) was also used to analyze the seasonal seismicity modulation. The average number of events per day increases by approximately a factor of two during cold seasons. Comparison of these results with snow cover thickness, the Lena water level, GNSS data, gravity data, and calculated additional Coulomb stresses revealed that the seasonal seismicity increase in the Lena Delta correlates with the positive additional Coulomb stresses under conditions of prevalence of normal faults in the Olenek segment. Additional Coulomb stress directly depends on equivalent water thickness, which, in turn, correlates with snow cover thickness. The summer flood does not have a significant impact on the seismicity rate, presumably due to its short duration.

At the BINP, the development, production and launch at JINR of a system for transferring a beam from the Booster to the Nuclotron of the NIKA complex was completed. The article discusses the equipment of monitoring and control subsystems, as well as describes the principles and composition of a software package based on the TANGO platform, designed to perform engineering manipulations with individual elements and suitable for work during acceleration sessions.

Budker Institute of Nuclear Physics of SB RAS has great experience in building power supplies used for accelerator applications where requirements for precise pulsing current are key features. The power supplies based on a capacitor discharge principle and typically with thyristors as switching element. The described power supply system consists of four charging units and a custom designed controller, it ensures the precision charging of the storage capacitors up to 1200 V of any polarity and switching it to the winding of the magnetic element.

It is established for the first time that biotite plagiogneisses from the Garevka metamorphic complex of the North Yenisei Ridge have geochemical characteristics of C-type adakites with island-arc melt sources. The Hf isotopic composition of zircons indicates the participation of several sources in the formation of the granite melt, including the juvenile mantle and older crustal rock protoliths with model ages THf(DM)с = 1838–1916 and 1965–2357 Ma, respectively. Based on the results of U–Pb dating of zircons, new pulses of Neoproterozoic endogenous activity at the western margin of the Siberian Craton (913 ± 11 and 915 ± 36 Ma for adakite-like granites and 932 ± 26 Ma for leucogranites), correlating with the Grenville tectonic events, were determined. These Grenville episodes of regional crustal evolution are correlated with the synchronous successions and a similar style of tectonothermal events along the Arctic margin of the supercontinent Rodinia. This confirms the spatial proximity of Siberia and the North Atlantic cratons (Laurentia and Baltica), which is consistent with the proposed Neoproterozoic paleogeographic reconstructions of Rodinia.

Modern ideas about the tectonics of the Eurasian continental margin are considered. Cratons, fold belts, platforms, and sedimentary basins are briefly characterized. A significant part of the Arctic continental margins is represented by folded structures of different ages. In the course of geological evolution, tectonic structures successively formed, modified and died off, on which the processes of rifting and ocean formation were superimposed. Multidirectional tectonic movements, both vertical and horizontal, which led to the formation of the contours of oceanic basins and the ridges separating them, also influenced the continental margin. The destruction of the continental crust of the outer part of the continental shelf resulted in the formation of graben-like and rift troughs. The history of the Arctic oceanic basin began with the opening of the straits that connected the once isolated basin, the waters of which were largely desalinated. The latest stage of development was characterized by processes in which the transgressions and regressions of the Arctic Basin, the development and degradation of terrestrial and underground glaciation, and other processes played a leading role.

This paper reports the obtained analysis data on the focal mechanisms and general distribution of earthquake epicenters in the Laptev Sea region. The principal stress axes directions were calculated by the formal stress inversion method for four groups of event clusters with known focal mechanisms. The distributions of the earthquake epicenters and crust thickness were compared. According to the seismological data, the extension axis of the Gakkel Ridge on the Laptev Sea shelf currently continues in the vicinity of the group of extension detachments located along the eastern boundary of the Anisin, Zarya, and Belkovskii–Svyatonosskii rift chains. The more ancient extension axis located along the group of detachments marking the eastern boundary of the Ust’-Lena and Omoloi rift systems and continuing the Gakkel Ridge axis is currently much less active. It carries residual stresses near its intersection with the Khatanga–Lomonosov fault zone in the northwestern parts of the shelf area and with the Lena–Taimyr zone of boundary uplifts, in the southwestern part. The axes oriented along the Olenyok and Bykovskii channels and the Siberian Platform boundary form extension conditions in the eastern part and strike–slip conditions in the western part of the Lena delta area.

The bottom sediments of the Russian Arctic seas have been studied to varying degrees. The least attention has been paid to the East Siberian Sea, the Quaternary geology of which remains largely overlooked. This article summarizes the results of a comprehensive research on the East Siberian Sea, including the first paleomagnetic analysis of nine sediment cores collected during three cruise expeditions as part of the program “State Geological Mapping of the Territory and Continental Shelf of the Russian Federation at the Scale of 1:1 000 000”. The results obtained show that the processes and conditions of sedimentation vary in different parts of the East Siberian Sea.

The article describes the first find of authigenic carbonates on the southern flank of the Gakkel Ridge in the zone of its junction with the Laptev Sea continental margin of the Russian Federation. The samples are represented by dense magnesian calcites and aragonites, including rounded and angular fragments of terrigenous material, as well as microphytoplankton of different ages, spores and pollen of terrestrial and aquatic plants. Elemental and organochemical characteristics indicate the predominance of oxidizing or intermediate between oxidizing and reducing conditions of carbonate crystallization, which may be a consequence of their formation near the bottom surface. The isotopic composition of O, C, and Sr allows us to conclude that the diagenetic carbonates of the Gakkel Ridge were deposited mainly in isotopic equilibrium with bottom water at a temperature of about 0°C, which corresponds to measurements from the ship. A wide range of δ13С (–23.5 до –37.3) indicates that methane was an important, but not the only source of carbon in carbonates. The wide variations in the 87Sr/86Sr (0.70906–0.70933), which correlate with the δ13С values, show that the carbonate-forming fluid was not only modern sea water, but also diagenetic solutions coming from the sedimentary cover together with methane and the products of methane and organic matter oxidation. Intense discharge of heterogeneous methane-bearing fluids may be related to the high modern tectonic activity of the studied region.

Molecular and stable isotope compositions of hydrate-bound gases collected from 59 hydrate-bearing sites between 2005 to 2019 in the southern and central sub-basins of Lake Baikal are reported. The δ 2 H of the hydrate-bound methane is distributed between − 310‰ and − 270‰, approximately 120‰ lower than its value in the marine environment, due to the difference in δ 2 H between the lake water and seawater. Hydrate-bound gases originate from microbial (primary and secondary), thermogenic, and mixed gas sources. Gas hydrates with microbial ethane (δ 13 C: − 60‰, δ 2 H: between − 310‰ and − 250‰) were retrieved at approximately one-third of the total sites, and their stable isotope compositions were lower than those of thermogenic ethane (δ 13 C: − 25‰, δ 2 H: − 210‰). The low δ 2 H of ethane, which has rarely been reported, suggests for the first time that lake water with low hydrogen isotope ratios affects the formation process of microbial ethane as well as methane. Structure II hydrates containing enclathrated methane and ethane were collected from eight sites. In thermogenic gas, hydrocarbons heavier than ethane are biodegraded, resulting in a unique system of mixed methane-ethane gases. The decomposition and recrystallization of the hydrates that enclathrate methane and ethane resulted in the formation of structure II hydrates due to the enrichment of ethane.

Ikaite is a metastable calcium carbonate hexahydrate (CaCO3 center dot 6H(2)O), which naturally occurs in environments characterized by temperatures of -2 to + 7 degrees C. It is therefore considered as an indicator of cold water conditions, although its suitability as a paleotemperature indicator is still questioned, especially as under certain laboratory conditions, ikaite was formed at temperatures of up to 35 degrees C. At warmer temperatures, ikaite becomes unstable and quickly decomposes to anhydrous calcium carbonate(s) and water. However, the primary ikaite crystal morphology can occasionally be preserved as a pseudomorph, generally known as `glendonite'. Even in early studies, glendonites were considered as indicators of cold climates due to their association with cold water fauna, dropstones and other cold climate indictors. We are using a global glendonite database with more than 900 occurrences to reconstruct their distribution through Phanerozoic time. Based on these reconstructions we observe that the Early Paleozoic glendonites cannot be directly correlated with cooler global climate episodes, but are restricted to the upwelling of cold waters on the wide shelf of the Baltic paleobasin. Carboniferous-Permian occurrences correlate with the Late Paleozoic Ice Age, one of the longest and most prominent glacial events in Earth's history. Our plate reconstructions suggest that most Late Paleozoic glendonite occurrences are restricted to the high latitudes. Glendonites are absent from Triassic and Upper Cretaceous sediments around the world, which were deposited during periods generally considered as the hottest of the Phanerozoic. However, glendonites are numerous within certain Jurassic and Cretaceous strata deposited during well-known cooling intervals. Our reconstructions suggest that the majority of Mesozoic glendonite occurrences are confined to the polar or near-polar regions. Paleogene-Neogene occurrences are restricted to the middle and high latitudes of the northern hemisphere. In addition to glendonites from marine deposits, a few findings are known from continental environments. Quaternary ikaites and glendonites have a widespread distribution in marine settings close to polar seas (mainly Arctic shelves) or on deep-water continental margins (e.g., Zaire deep fan, Nankai Trough, Sakhalin Island slope), with rare findings in terrestrial environments such as lakes, ice sheets and caves. In contrast to Quaternary occurrences, the older Mesozoic and Paleozoic glendonites are confined to shallow marine shelf environments. This discrepancy is likely to be related to the lower preservation potential of deepwater and terrestrial sediments in deep time, as opposed to sediments deposited at high rates along the margins of epicontinental or marginal seas.

The gas hydrate-bearing structure-mud volcano Kedr-1 (Lake Baikal, southern basin)-is located near the coal-bearing sediments of the Tankhoy formation of Oligocene-Miocene age and can be an ideal source of gas-saturated fluid. A significant amount of siderite minerals (FeCO3 ) were collected from sediments at depths ranging from 0.5 to 327 cm below the lake floor (cmblf). An important feature of these carbonate minerals is the extremely strong enrichment in the heavy 13 C isotope, reaching values of +33.3‰ VPDB. The δ13 C of the siderite minerals, as well as their morphology and elemental composition, and the δ13 CDIC of the co-existing pore water, differed across layers of the core, which implies at least two generations of siderite formation. Here, we leverage mineralogical and geochemical data with 16S rRNA data from the microbial communities in sediments surrounding layers containing siderite minerals. Statistical data reveal the formation of three clusters of microbial communities based on taxonomical composition, key taxa among bacteria and archaea, and environmental parameters. Diversity and richness estimators decrease with sediment depth, with several similar prevailing clades located at the bottom of the core. Most of the taxa in the deep sediments could be associated with putative metabolisms involving organotrophic fermentation (Bathyarchaeia, Caldatribacteriota, and Chloroflexota). Various groups of methanogens (Methanoregulaceae, Methanosaetaceae, and Methanomassiliicoccales) and methanotrophic (Methanoperedenaceae) archaea are present in the sediment at variable relative abundances throughout the sampled depth. Based on the physicochemical characteristics of the sediment, carbon isotope analysis of carbonate minerals and DIC, and phylogenetic analysis of individual taxa and their metabolic potential, we present several models for subsurface siderite precipitation in Lake Baikal sediments.

In 2007–2015, Shirshov Institute of Oceanology of the Russian Academy of Sciences (IO RAS) carried out seismological observations in the water area and on the coast of the Baltic Sea using autonomous seismic stations. Here, in the area of the Sambia Peninsula, previously considered aseismic, a strong perceptible earthquake with a magnitude of about M = 4.6 occurred in 2004. The most interesting data were obtained by IO RAS in 2008–2009 from seismological monitoring using autonomous bottom and coastal seismic stations. The data obtained in 2010–2015 turned out to be unsuitable for full-scope processing due to several causes (losses of bottom seismographs, high noise level at coastal stations, etc.). Seismological monitoring in the west of the Kaliningrad region and in the adjoining area of the Baltic Sea detected weak earthquakes with magnitudes ML = 2.5-3 whose sources are confined to the development are of the Kravtsovskoe offshore oil field. Some of these earthquakes have been recorded by the stations of the Norwegian seismic array NORSAR and by the seismic stations of Sweden. The Kravtsovskoe oil field is located on the shelf northwest of the unique natural object, the Curonian Spit. The detected weak earthquakes are likely to be anthropogenic, induced by reservoir pressure disturbances as a result of intensive hydrocarbon production, and are probably precursors of a strong man-made earthquake.

The power supply system for the electromagnets of the electron storage ring of the SKIF common use center (CUC) includes five types of stabilized current sources totaling 2259. The maximum output current of the power supplies is from 3 to 800 A, the output power is from 70 to 300 kW, and the permissible instability of the output current is from 10 to 100 ppm. For reliable operation of the light source, it is necessary to ensure the stability of the parameters of the current sources, high reliability of operation, and the fast replacing failed power supply source within the same type.

Outcrops of the coal-bearing Tankhoi Formation (Oligocene–Pliocene), traced along the southern shore of Lake Baikal, submerge under its Southern Basin, where several hydrate-bearing zones of the focused hydrocarbon fluid discharge have been found. To test the hypothesis that coals of the Tankhoi Formation can be the sources of hydrocarbon gases in these zones, we collected coal samples from the Shakhterskaya Gorka outcrop. Experiment on gas generation from the selected samples was carried out in a special autoclave at a temperature of 90°C for eight months. This paper presents the obtained results, which confirm an important role of the process of gas generation from coals in the formation of fluids in the Kedr mud volcano. The further migration of gases was accompanied by the biodegradation and formation of secondary microbial methane due to CO2 reduction. This was one of the reasons for the carbon isotopic pattern observed in methane (heavier than –50‰ VPDB) and carbon dioxide (positive values) taken from the near-surface sediments and hydrates of the Kedr mud volcano, as well as for the significant enrichment of authigenic siderites in the heavy 13C isotope.

OBS observations in the Persian Gulf during a short time span have revealed the occurrence of low magnitude (ML = –0.2–2.9) earthquakes with hypocenters in the mantle beneath the Gulf and beneath the Zagros Mountain Massif. A cross-section across the shoreline of the Persian Gulf shows the projections of these hypocenters beneath the Zagros Mountains to make inclined layers that dip northeast at a high angle into the mantle down to depths of 120‒180 km. The 3D distribution of large and moderate magnitude earthquakes based on an improved earthquake catalog as reported by the US Geological Survey and by the International Seismological Centre (ISC) is not at variance with the distribution of microearthquakes and low magnitude earthquakes but seems rather to supplement it, forming a separate seismic dipping layer. According to the data acquired by OBS observations, seismic activity occurs throughout the entire crust and upper mantle of the region rather than in the upper crustal layers only as was asserted in previous publications. It is possible that collision and accompanying phenomena (mantle seismicity and destruction of the granitic layer in the crust) are related to the hypothetical rotation of the Earth around the center of rotation placed at Cyprus Island.

The power supplies presented in this article are used as part of the charged particle beam orbit correction system of the injection complex at SRF SKIF. The MPS-20 and MPS-6 (magnetic power supply) and PA-3 (power amplifier) power suppliers presented in the paper can provide electromagnets with currents reaching ±20, ±6, and ±3 A, respectively. All power sources are remotely monitored and controlled via the Ethernet and are made using modern components according to the Euromechanics standard.

This paper performs a detailed study of a wide set of organic-geochemical proxies in 15 sediment cores collected from the main basins of Lake Baikal (the northern, the central and the southern) where processes of focused fluid discharge were detected. A variety of studied zones includes sites with gas and hydrothermal seepage, mud volcanoes with or without gas-oil fluid discharge, gas hydrates and authigenic carbonates. The composition of the dispersed organic matter and individual hydrocarbon molecular markers (n-alkanes, dimethyl alkanes, isoprenoids, steranes, terpanes and polycyclic aromatic hydrocarbons) testify to the input from predominantly allochthonous terrestrial and autochthonous microbial and algal sources. The studied sources, maturity and biodegradation parameters of organic matter vary significantly for areas with different fluid discharge. The composition of specific biomarkers including isoprenoids and immature hopanoids reflects the lateral and vertical changes of microbial activity in sediments associated with various environmental conditions. The identified types of terpanes distribution (mature, mixed and immature) correlate well with types of fluid discharge and attest to the development of various methanogenic and methanotrophic microbial communities in sediments. Moreover, the revealed specificity of microbial molecular markers distribution allowed us to suggest the fluid discharge processes in zones where they were not previously detected.

Our study considers the structure and tectonics of the Novaya Zemlya archipelago, located in the west Russian Arctic and part of the Eurasian Arctic: (i) the age of the Pre-Paleozoic basement of the North block of the archipelago and the geodynamic sedimentation conditions in its northern end, where many kilometers of turbidite sedimentary strata accumulated in the paleobasin during the Late Vendian-Silurian; (ii) the significance of Caledonian tectogenesis in the geological history of the archipelago; (iii) the age and causes of the Late Hercynian (?)-Early Cimmerian orogeny in the Novaya Zemlya archipelago and the relationship of the archipelago structures with the structures of the Urals; (iv) the age and causes for the formation of the modern relief of the Novaya Zemlya archipelago; (v) evidence of active movements of the shelves of the Barents and Kara Seas surrounding Novaya Zemlya. The age of the most ancient rock dating in the area of the Main Novaya Zemlya Fault corresponds to the Vendian (598 ± 26; 609 ± 4 Ma), and the model age of the protolith is estimated at 1 Ga. Two blocks have been established for the Precambrian (North and South) and three, for Middle-Late Paleozoic (North, Central and South). The Middle-Late Paleozoic stage is considered as a reflection of the tectonic-magmatic activation manifested in the Caledonides of Greenland and Scandinavia. The episodes of basic and granitoid magmatism in the intervals of 730–690 and 610–590 Ma indicate the presence of blocks of the former Arctida (?) in the west (Novaya Zemlya), in the central part (Severnaya Zemlya), and in the east (New Siberian Islands and Wrangel Island) of the modern Arctic. Basic areal (plume) magmatism occurred in the Late Devonian, in the Late Permian-Early Triassic and Late Mesozoic. The features of the geological structure of the Novaya Zemlya archipelago strictly correspond to the three orographic areas (tectonic blocks) of the archipelago. The Western and Eastern Novaya Zemlya troughs are the tectonic pairs with the Novaya Zemlya orogen. The heights of the dated sea terraces indicate significant rates of neotectonic uplift of the archipelago.