Vol 515, No 2 (2024)

New U-Pb data for zircon in the Konchezersky Sill provide robust age constraints for the Suisari Fm in the Onega Basin and constrain the maximum age limit for the sedimentary successions of the Zaonega Fm and the Shunga isotope event.

Mineralogical and U-Pb (ID-TIMS) geochronological studies of garnets from three types of scarn associations of the Khovu-Aksyn Ag–Bi–Cu–Ni–Co deposit (Republic of Tyva) were carried out. The U-Pb garnet age estimate (404±2 million years) is close to the Early Devonian stage of basitic and alkaline-basitic magmatism identified within the Tuva trough of the Altay-Sayan folded region. The age of the scarn formation and the associated with it early stage of mineralization of the Khovu-Aksynskoye Ag–Bi–Cu–Ni–Co deposit has been established for the first time.

The Kalgan ophiolite massif is a unit of the ophiolite association of the Chersky collision belt. It is part of the Verkhoyano-Kolyma folded system on Northeast Asia. The Kalgan massif includes a complex of mantle peridotites, a lower-crust complex represented by ultrabasic cumulates, cumulative gabbro-amphibolites and amphibolites, and an upper-crust complex represented by metabasalts. New geochemical data obtained by the ICP-MS method, as well as data on the isotopic composition (Sm, Nd), made it possible to significantly clarify the geodynamic conditions for the formation of volcanites and to determine the features of the sources of parent melts.

The estimates of the scale and distribution of Bering Sea waters in the Pacific sector of the Arctic Ocean were made using the high-precision data on the isotopic composition and concentration of dissolved inorganic carbon. Despite the fact that δ¹³С(DIC) and [DIC] are not classic conservative tracers, in the East Siberian Sea, which is a zone of active interaction of river runoff with sea waters, these parameters can indicate the presence of sea waters not only of Atlantic, but also of Pacific origin, similar to the waters of the Bering Sea. Using a three-component mixing model, the spatial distribution of Pacific, Atlantic and river waters along two sections of the East Siberian Sea was estimated. The Pacific component extends from east to west to approximately 160 degrees east longitude, and possibly further west, skirting Wrangel Island not only from the north, but also possibly from the south. In the East Siberian Sea, waters similar to the open sea Bering summer surface waters are found, which are carried to the northern shelf by the circular Bering Sea Current, and upper intermediate waters, which can enter the zone of the northern shelf of the sea due to upwelling or active mixing.

The paper presents the geological, geochemical and isotope-geochronological studies of the Rudny Altai granitoids in the west of Central Asian Orogenic Belt (CAOB) – the front part of the Altai convergent margin of the Siberian continent. Isotopic U–Pb dating of zircons showed an age range from 367 to 363 Ma. Geochemical characteristics indicate the relevance of leucogranites to calc-alkaline high-K series (SiO₂ > 73 wt.%, Na₂O+K₂O = 6.9–9 wt.%, Na₂O/K₂O = 0.7–1.2), with calc-alkaline and alkaline-calcic affinities (MALI = 6.32–8.41). They bear meta- to weakly-peraluminous values (A/CNK = 0.9–1.2), high Fe* index (0.84–0.97) and high fluorine (0.04–0.17 wt.%) content. Variations of HFSEs, LILEs contents, Ga/Al ratios and strong negative A/CNK-P₂O₅ correlation indicate their affinity with fractionated I-type granitoids. Rare metal (beryllium) mineralization is spatially and genetically related to leucogranites. It is assumed that the formation of granitoids was associated with shearing setting at the convergent margin of the Siberian continent, as a result of oblique subduction of the Irtysh-Zaisan ocean plate.

The first case of hydrothermal brecciated crusts composed of goethite with quartz veinlets for the Sea of Japan is described.

The history of the crustal subsidence in the Mesozoic and Cenozoic in the West Siberian Basin – the largest sedimentary basin in the world – is considered. Most researchers associate its formation with post-rift subsidence of the crust, which followed an episode of strong lithospheric stretching about 250 million years ago near to the Permian to the Triassic transition. A characteristic feature of post-rift subsidence is a decrease in its rate in time. During the Mesozoic-Cenozoic history, in Western Siberia the rate of crustal subsidence should have slow down by an order of magnitude. However, the analysis of long (700–900 km) seismic profiles in the north of Western Siberia and in the Southern Kara Sea shows that since the beginning of the Mesozoic in these regions, on average, there has been an acceleration of the crustal subsidence. Under such circumstances, lithospheric stretching in them could be responsible for only a small part of the total subsidence of the crust of 6–7 km. In Western Siberia, the Earth’s crust is close to the isostatic equilibrium. Then, in the absence of strong stretching, the accumulation of thick sedimentary sequences in the basin could only have been caused by rock contraction in the lower crust due to prograde metamorphic reactions. To obtain the above results, we used, for the first time, some simple methods to analyze the structure of the sedimentary cover in the West Siberian Basin. Detailed seismic profiles have been published for many other deep basins on all the continents. The methods of their interpretation implemented in this paper can be easily applied to determine the role of lithospheric stretching in the formation of deep sedimentary basins on the global scale.

We present the results of instrumental observations of acoustic oscillations, geomagnetic variations and variations of the atmospheric electric field during the fall and explosive destruction of the bolide in the southeast of Turkey on September 02, 2023. It is shown that the destruction of the bolide under the action of aerodynamic forces, which occurred in three stages, was accompanied by an acoustic signal of a characteristic shape and manifested in variations of the magnetic and electric fields in the near-surface layer atmosphere. The total energy of the event, estimated by the acoustic effect, was ~ 9×10¹² J, which corresponds to about 2.15 kt in TNT equivalent. The maximum amplitude of geomagnetic variations caused by the explosion of the bolide ranged from 0.2 to 2.1 nT depending on the distance. At the same time, the amplitude of variations of the vertical component of the atmospheric electric field at the Mikhnevo observatory (distance ~1900 km) was ~70 V/m. The ionospheric effect of the event under consideration is demonstrated in the form of variations of the critical frequency f₀F2 obtained as a result of processing ionograms of height-frequency sounding of the ionosphere at the Rome station.

We used the hydrodynamic model of the Caspian Sea, INMIO-CICE, to calculate equilibrium river runoff and evaporation from the sea surface over a wide range of sea levels (from –85 to +50 m asl) for different climatic conditions: the Last Glacial Maximum (about 21kyr) and pre-industrial climate (~1850 CE). Data from the climate model INMCM4.8 were used as boundary conditions. It was found that to maintain sea level at 35–50 m asl, corresponding to the maximum values of the Khvalynian transgression, a river runoff of about 400 km3/year was required in the Last Glacial Maximum. In the Last Glacial Maximum evaporation from the sea surface decreased by 105–170 mm (12–22%), and precipitation, according to the INMCM4.8 model, by 50–70 mm (15–30%). This caused the equilibrium runoff to decrease by about 10–20% compared to pre-industrial conditions. Smaller absolute and relative changes correspond to lower sea levels. The maximum decrease in evaporation occurred at 5 m asl.

The paper presents the results of a comprehensive study of well sections drilled on the coastal spits of the Taganrog Gulf of the Sea of Azov and bottom sediment columns selected in the water area. A detailed analysis of the early malacological communities, an important participant in the sedimentary process, made it possible to trace changes in their living conditions in the Holocene. Based on determining the absolute age (¹⁴C) from the valves of mollusk shells buried in situ, it is shown that at the beginning of the Phanagorian regression, in the area of the distal part of the Dolgaya Spit, there was a sea reservoir with an Azov-Black Sea complex of reference species. Based on the results of palynological analysis, changes in the natural conditions of the Azov region over the past few thousand years have been reconstructed and arid and humid climatic phases have been identified.

The article presents the results of studies to assess the effect of humic acids, taken at a concentration of 250 ppm, on the process of induced phytoextraction of heavy metals from soils selected near Norilsk. Phytoxtraction was carried out by different types of marigold plants: Tagetes patula and Tagetes erecta. The studies were carried out in greenhouse conditions under controlled spectral illumination (light culture). The duration of the experiment was 21 days. A short vegetation period was chosen based on the conditions of a short summer period typical for this region, where it is more rational to keep records of the systemic removal of toxicants from contaminated soils by several cycles of their sowing/cutting per season, already at the juvenile phase of ontogenesis. For elemental analysis, the method of atomic emission spectrometry with inductively coupled plasma was used. To assess the level of efficiency of metal accumulation, the authors developed and used the original computing neural network CompNN, which allows calculating the cognitive significance index (CSI) based on empirical data on the accumulation of toxicants, both in shoots and roots of plants. The results of the study showed that the introduction of an organic additive in the form of humic acids into the soil led to inhibition of the growth of the above-ground part of T. patula. As for T. erecta, the rate of accumulation of green plant biomass did not change when humic acids were added. The decrease in the biomass of shoots of T. patula plants is explained by an increase in the accumulation of metals in them by an average of 91.6% for the variants. The content of metals in the shoots of T. erecta under the influence of humic acids, on the contrary, decreased by 17.3% on average. A similar result was observed in relation to the root zone: the trend of change in the fixation of metals for both plant species here was 40.8 and 10.8%, respectively. Calculation of CSI indices also showed that the addition of humic acids in T. patula increases the intensity of metal accumulation from the soil in its biomass in all variants, while in T. erecta, on the contrary, it decreases. The performed cluster analysis demonstrated the fixation of metals in the main buffer zone of plants, and also made it possible to isolate nickel into a separate homogeneous series. With regard to the distribution of this element in the shoots by variants, experience has shown that it has demonstrated here the proximity of convergence with copper. The correlation coefficients of their accumulation with the CSI index in the shoots of both plants were r = 0.82; 0.87 for Cu and r = 0.87; 0.83 for Ni. The proximity of these values indicates the priority nature of the accumulation of these metals in the plant biomass of marigolds, and also characterizes the manifestation of certain interactions between them in contaminated soil by the type of antagonism or synergism.