Vol 512, No 1 (2023)

The results of detailed geological and geomorphological studies in the waters of the Pechora Sea using a complex of hydroacoustic methods in the 52 cruise of the R/V “Academic Nikolaj Strakhov” revealed numerous gas funnels (pockmarks) at the bottom of the Yuzhno-Novozemelsky trench. These forms are widespread on most of the bottom of the Barents Sea, while on the Pechora shelf there is very little information about their distribution. Analysis of seismoacoustic sections at the sites of development of gas funnels showed the presence of vertical chimneys in unconsolidated sediments of the Yuzhno-Novozemelsky trench, through which gas rises to the bottom surface and its release into the water column with the formation of negative landforms, which is accompanied by churning bottom sediments.

With the aim to improve our understanding of the age and genesis of the Neoproterozoic diamictites of the Middle Tianshan of Kyrgyzstan, we studied the late Precambrian strata of the Sandalash, Talas and Chatkal Ranges. The results of detrital zircon dating indicate that diamictites were deposited in the Cryogenian and Ediacaran. Diamictites in the lower part of the Shorashu Formation comprise tillites and were likely deposited during the Marino glaciation ca 640–635 Ma. Diamictites in the upper part of the Shorashu Formation represent debris flows and grain flows associated with turbidites and, apparently, have non-glacial origin; their age is not older than the early Ediacaran 616 ± 7 Ma. The pinching out of the Shorashu Formation to the north and the predominantly southerly directions of sediment transport in turbidites indicate that a non-depositional uplift located north of the basin. The distributions of detrital zircon ages in the studied samples are characterized by large peaks at 0.7–0.8 and 1.8–1.9 Ga and small peaks at ca 2.4–2.5 Ga and are almost identical to the age distributions in the Proterozoic sediments of the Tarim Craton. Comparison of the studied strata with key sections of the Kuruktag Range in the NE Tarim suggests that the diamictites of the lower part of the Shorashu Formation are analogues of late Cryogenian Tereeken tillites, and the slope facies of the upper part of the section are analogues of the early Ediacaran turbidites of the Zhamokti and Yukkengol Formations.

The paper presents the first data of the isotopic zircon U–Pb study (LA–ICP–MS method) on the granodiorite-granite from the Sardara (Sarykty) pluton in the district of the giant Muruntau Au deposit in the Western Tien Shan (Uzbekistan). In a single sample, three age groups of zircon crystals identified, with their concordant U–Pb age being 322.0 ± 3.7 Ma (MSWD = 3.1, 4 zircon grains), 301.6 ± 2.1 Ma (MSWD = 0.17, 11 zircon grains), and 289.1 ± 4.9 Ma (MSWD = 0.98, 2 zircon grains), respectively. The scatter of the isotope age data obtained can be interpreted using the model of subsequent crystallization of various zircon generations in variably-deep magmatic batches, followed by zircon capturing during the magma differentiation and crystallization. Notable is a quite close coincidence of the two (the younger) age intervals to the concordant U–Pb zircon ages, which were published before for the granitoid rocks found directly at the Muruntau deposit. The latter thus can represent the dike “splits” occurred at the respective stages of the magma evolution (progressing differentiation) in the deeper batches of the granitoid magma, with its larger intrusions represented by the Sardara (Sarykty) and other plutons outcropping at some distance from the deposit. Overall, the older isotopic U–Pb zircon data of the Sardara (Sarykty) pluton (in the order of 322 Ма and 302 Ма, respectively) correspond closer to the subduction event, whereas the younger U–Pb zircon data (in the order of 289.5 Ma) are quite relevant to the post-collisional stage occurred in the region. Therefore, the initiation and initial development of the magma batches in the Muruntau deposit district could occur in the subduction environment but the final granitoid magma differentiation and crystallization were completed already at the post-collisional stage.

Being an abundant mineral phase of high-grade rocks, rutile is used as a tracer of lithospheric evolution for deep zones of orogenic belts. This study presents the new ID-TIMS U–Pb geochronological, mineralogical and geochemical data for rutile from the North Muya block (Baikal-Muya Foldbelt) eclogites in order to examine the applicability of its age estimates relative to the exhumation process of high-grade rocks. The assemblage of mineral inclusions in rutile (mainly titanite, epidote and amphibole) indicate rutile growth through titanite breakdown reactions during prograde metamorphism epidote-amphibolite or amphibolite-facies rocks. The range of Zr contents and estimated Zr-in-rutile crystallization temperatures correspond to conditions from prograde (619–638°С at 1.5 GPa) till peak ones (659–684°С for 2.5 GPa). The U–Pb age estimate (604 Ma) is notably younger than that of peak eclogitic metamorphism (630 Ma), and highlight the protracted cooling history of eclogite-bearing complex during its evolution below closure temperature of the U–Pb isotope system (~500–525°С) during tectonic unroofing or erosion of continental complexes.

In this work, a crystal chemical analysis of the known experimentally deciphered crystal structures of tetrahedrite group minerals was carried out in order to reveal the relationships between the occupancies of anion crystallographic sites in the structures, their effective sizes and unit cell parameters. To achieve this aim, we analyzed the effective sizes of the 24g and 2a anion sites in 68 deciphered crystal structures of tetrahedrite group minerals according to the published data. The analysis was carried out using the TOPOSPro software package by partitioning the space into Voronoi–Dirichlet polyhedra (VDP). It has been shown theoretically for the first time that the content of a large sulfur ion and its deficiency affect the unit cell parameter. A linear correlation between the VDP volume of the anionic site of S^2– (24g) and the unit cell parameter in minerals of the tetrahedrite group was established, which shows that the anionic substructure dictates the structural motif in this class of compounds. It was found that the change in the VDP volumes of sulfur anions is associated with different occupancies of anionic sites. It is found that the formula (unit cell) of the compound contains fewer than 13 sulfur ions in almost all deciphered crystal structures of tetrahedrite group minerals. It was concluded that the calculated VDP volume of the 24g anionic position less than 22 ų indicates a significant deficit in the anionic substructure. It was shown that, using information about the VDP volumes of all anionic and cationic sites in the structure, it is possible to predict the unit cell parameters of minerals of the tetrahedrite group with an accuracy of 0.01 Å

Taragai peridotite massif is interpreted as an explosive ultramafic pipe emplaced through the Neoproterozoic carbonate skarnoids and Early Paleozoic granites of the western Bureya terrane. Peridotites at the surface are represented by strongly eroded bowl-shaped structure filled with disintegrated explosive material containing abundant peridotite boulders and host rock xenoliths. Explosive character of the Taragai massif is further emphasized by the occurrence of magnetite, iron-carbonate-silicate (with magnetite) and Cu-Ag-Au microspherules characteristic of explosive eruptions. Formation of the Taragai ultramafic pipe is related to the assimilation of mantle wedge or lithospheric mantle material over the stagnant Izanagi slab by the ultra-hot and reduced upwelling fluid flow within the transform-type continental margin tectonic setting.

A wide range of geological and geophysical methods was carried out on the Yamal Peninsula in the Arctic in the period 2014–2022. The results were analyzed together with data from remote sensing of the Earth. Fundamentally new data on the gas-dynamic mechanisms of dangerous processes in permafrost have been obtained. These data included catastrophic gas blowouts and explosions with the formation of giant craters. More than three thousand zones of powerful gas blowouts with the formation of craters at the bottom of thermokarst lakes, rivers, and the coast of the Kara Sea have been discovered. According to data on remote sensing of the Earth, large mud volcanic structures, located at the bottom of the Labvarto and Yambuto thermokarst lakes, were discovered on the Yamal Peninsula in 2022–2023 for the first time. Monitoring of their state with the use of retrospective satellite images showed the presence of periodic release of underground fluids, including gas. A conclusion was made about the discovery of active mud volcanoes on the Yamal Peninsula

A geodynamic model of the modern Earth is constructed based on the SMEAN 2 global seismic tomography model. On the basis of mantle temperature anomalies, numerical modeling of spherical mantle convection is performed for the parameters of the real Earth. For Antarctica, an explanation was obtained for the existence of the West Antarctic Rift System, which contains one of the largest and least known volcanic provinces on Earth, which is consistent with the increased surface heat flow and modern volcanism of the West Antarctic Rift System and part of the Antarctic Peninsula. The increased heat flow and volcanoes in this region are causing instability and accelerating the flow of glaciers from the West Antarctic Ice Sheet into the ocean, which could lead to a significant rise in global sea level.

A new locality Kimiltei, Irkutsk region, where unmineralized remains of arthropods were buried en masse, is described. U-Pb zircon dating indicated the Cambrian age and gave the youngest values 491 ± 6 Ma. Arthropods in Kimiltey are represented by Chasmataspidida, Synziphosurina and Euthycarcinoidea. The last two groups have not been known on the Siberian platform, and the first one has been described here only from the Devonian rocks. The Irkutsk finds fall into the ranks of the most ancient representatives of their groups, and their ranges turned out to be wider than previously known. Attention was drawn to their co- burial as the representatives of these groups have never been found together before. Taking into account that the descendants of all three groups gave rise to terrestrial lines of chelicerates and insects, thus the Kimiltey assemblage is the entire fauna of the land arthropods ancestors. Their co-habitation indicates they started their expansion on land from some close ecological niches in the intertidal zone.

The results of instrumental observations of acoustic oscillations and geomagnetic variations during the fall of the bolide on 04/19/2023 in the area of Kiev (Ukraine) are presented. It is shown that the explosion of the car was accompanied by an acoustic signal recorded at a considerable distance from the epicenter of the event (~755 km), and manifested itself in variations of the magnetic field. According to acoustic observations, 4 explosions of the largest fragments of the car were recorded. The total energy of the event was 4.2–10¹¹ J, which corresponds to about 0.1 kt in TNT equivalent. The maximum amplitude of geomagnetic variations caused by the explosion of the bolide at distances in the range of 454–909 km was from 2.5 to 4 Nt.

During the expedition on the R/V “Akademik Mstislav Keldysh” (81^st cruise) in 2020, extensive material was selected, representing columns of bottom sediments up to 6 meters deep in the Kara Sea. After lithological description of the columns, sediment samples were taken from different horizons for degassing of pore gases. The extracted gas samples were analyzed for the content of the main gases – methane (CH₄), carbon dioxide (CO₂) and light hydrocarbons. The characteristic features of CH₄ and CO₂ content changes with depth of bottom sediment at station 6879 (Kara Sea shelf) were studied. A model of gas diffusion was constructed taking into account the biochemical reactions of methanogenesis and methane oxidation. The rate of methane formation can be estimated by the value J ≈ 3 × 10^–10 μg sec^–1 L^–1 (per liter of sediment). The rate coefficient of methane consumption by microorganisms is K ≈ 0.5 × 10^–10 sec^–1. The methane flux from the bottom surface of the Kara Sea near station 6879 is q ≈ 3.47 × 10^–2 μL m^–1 year^–1.

The variability of the composition and properties of natural waters, which creates numerous difficulties in water use, cannot always be explained by the influence of external influencing factors, such as weathering or leaching of rocks, a change in the phases of the water regime, etc. This is especially true for subdiurnal and subhourly quality variability, which can be caused by complex, previously unknown dynamic hydrochemical processes. Such a conclusion follows from the results of the study of turbidity and pH of natural water given in the work, obtained with an increased frequency of measurements. These results indicate the existence of a quasi-cyclic change in the controlled parameters with different periods, from every minute to daily. The study of observational data allows us to make an assumption that in this case the hydrochemical dynamics is due to direct and reverse energy cascades in a two-dimensional turbulent flow of natural water, in which the impurity subsystem is prone to stratification.

The article presents the results of research for (2020–2021). The results of the influence of different doses of fulvic acid on increasing the life span of bees kept in entomological cages and improving their physiological state are given. The studies were carried out in laboratory conditions at an air temperature of +27 ± 2°C, on bees of spring-summer generation. The experiment included three groups of bees in triplicate. The first group – control, in this group, the bees consumed 60% sucrose solution as top dressing. In the second group, the bees consumed a 60% sucrose solution, to which fulvic acid was added, at the rate of 0.1 ml per 200 ml of solution. The third group was fed a 60% sucrose solution, to which fulvic acid was added, at the rate of 0.2 ml per 200 ml of solution. According to the results of the research, it was found that fulvic acid at a dose of 0.1 ml per 200 ml of solution contributed to the prolongation of the life of bees. In this variant of the experiment, 30–40% death of bees occurred five, and 50% and 60% four days later than in the control. Fulvic acid, where an increased dose was used, did not have a significant effect on the lifespan of bees. As the bees aged, fulvic acid in both variants of the experiment reduced the load on the rectum and toxicity to the body, thereby improving their physiological state.