Том 510, № 2 (2023)

Isotope-geochronological and geochemical data and age of the metamorphic rock of the Butugol metamorphic Complex, located in the eastern part of the Tuva-Mongolian microcontinent of the CAOB, have been obtained. It has been established that the gneisses protolith is, in one case, volcanic rocks with an age of 1009 ± 8 Ma, in the other case, potassium meta-sedimentary rocks accumulating in continental marginal basins. The formation of the protolith of the metavolcanogenic rocks of this complex took place at the turn of the Meso- and Neoproterozoic on the formed crust, while the metasedimentary rocks formed due to the Mesoproterozoic, more rarely Paleoproterozoic and Archean continental provenances. It has been established that the rocks of the Butugol metamorphic Complex have a different history of development from other blocks of the earth’s crust as part of the composite Tuva-Mongolian microcontinent.

In this paper we provide primary data on multi-isotope sulfur composition of the Neoarchean BIF sulfides of the Kostomuksha greenstone belt in Karelia (the Karelian Craton on Fennoscandian Shield). These sulfides formed at 2760–2740 Ma. Pyrite associated with fine-grained magnetite showed negative δ³⁴S values (up to –7.8‰) and positive Δ³³S values (up to +0.7‰). At the same time, pyrrhotite of vein-disseminated ores associated with shale demonstrated both negative δ³⁴S (up to –6‰), and Δ³³S values (up to –0.46‰). Based on the obtained data we assume that sulfur for the BIF sulfides was transported from three reservoirs: - atmospheric (photolytic), hydrospheric (seawater sulfate), and magmatogenic. Sulfur isotope ratios in sulfides preserved the evidence of interaction between abiological (atmospheric, hydrothermal) and biological processes (dissimilatory microbial reduction) that occurred during the formation of iron ore deposits of the Kostomuksha greenstone belt in Karelia.

The study provides whole-rock geochemical and Rb-Sr and Sm-Nd isotope examinations of Permian-Triassic volcanics (basalts, basaltic andesites) and sills (trachydolerites, monzodiorites) from the Kuznetsk Basin, which is part of the Siberian Large Igneous Province. It is shown that the volcanic section of the Kuznetsk Basin consists of the Lower (I and II units: TiO₂ = 1.6–1.9 wt.%, Gd/Yb = 2.0–2.1) and Upper (III–VIII units: TiO₂ = 1.4–1.8 wt.%, Gd/Yb = 1.7–1.9) Sequences. The Mayzass sill is geochemically correlated with the Unit II basaltic andesite of the Lower Sequence, and the Syrkashev sill is geochemically akin to the Upper Sequence. The Kuznetsk traps originated from the partial melting of a Sr-Nd isotopically heterogeneous subduction-modified lithospheric mantle. They are geochemically comparable to low-Ti basalts of the low–middle Nadezhdinsky suite from the Noril’sk region, but differ in Sr-Nd isotope composition. The Sr-Nd isotope signatures of the uncontaminated lavas and Syrkashev sill rocks (εNd(T) = (+4.6)–(+2.4), (⁸⁷Sr/⁸⁶Sr)_T = 0.7047–0.7054) are inherited from the ancient lithospheric mantle and do not represent the contribution of the Siberian plume. The Mayzass sill rocks (εNd(T) = (+2.2)–(+2.1); (⁸⁷Sr/⁸⁶Sr)_T = 0.7055–0.7063)are derived from a parental melt contaminated with crustal carbonates.

The crystal structure of rare titanosilicate cariochroite was deternined using X-ray powder and srlected area diffraction data. The crystallochemical formula proposed – [Na(Sr_0.5Ca_0.5)Mg]₃[Fe\(_{8}^{{3 + }}\)Mn(\({\text{Fe}}_{{0.5}}^{{2 + }}{\kern 1pt} {{\square }_{{{\text{0}}{\text{.5}}}}}\))]₁₀(Ti₂Si₁₂)O₃₇(OH)₁₄(Н₂О)₃. Monoclinic unit cell parameters are: a 16.550(3), b 5.281(2), c 24.25(3) Å, β 93.0°, Z = 2, sp. gr. P2/n. The crystal structure represent the new type of complex Ti–Si–nrt, provided the big volune canals contaning some exchange cations, OH groups and water molecules.

Eastern Transbaikalia is a unique rare-metal province of Russia. Most of the studied deposits are associated with granitoid intrusions. Despite the high degree of knowledge of regional magmatism, a number of questions remain related to both the belonging of specific massifs to magmatic complexes and the correlation of certain complexes within various structural-formation zones. This paper compares the material composition and age of several petrotypical and parapetrotypical massifs classified as Late Mesozoic complexes distributed within the Aginskaya, Prishilkinskaya, and Argunskaya structural-formational zones of Eastern Transbaikalia. Based on the results of U-Pb dating, two stages of granitoid magmatism have been established: 1) the end of the Middle – the beginning of the Late Jurassic (163–156 million years ago) and 2) the beginning of the Early Cretaceous (142 million years ago). It is shown that the closely aged rocks of the Borshchovochny, Amudzhikano-Sretensky and Shakhtama complexes have similar material characteristics, while the rocks of the Kukulbey complex (from three massifs) vary in composition. Elevated δ¹⁸O values (from +10.8‰ to +11.9 ‰) for the rocks of the Jurassic complexes indicate their formation mainly due to the melting of crustal material, and lower δ¹⁸O values (from +9.8 ‰ up to +10.3‰) for the Early Cretaceous granitoids suggest the contribution of a mantle source to their genesis.

In the geological history of the Earth, there has been a significant change in the composition and areas of formation of carbonate deposits, which reflects the general evolution of methods, paleogeographic and geochemical settings during this time, and different stages in this evolution. At the Archean-Proterozoic boundary, acidic conditions in impounded bodies changed to moderately acidic, which is seen in the appearance of iron carbonates. The second frontier is the Siderian-Rhyacian boundary, when intensive assimilation of CO₂ led to the formation of alkaline conditions in impounded bodies and the accumulation of magnesian carbonates. Carbonate accumulation itself occurred in the impounded bodies of continental block. The third milestone is the Vendian-Cambrian boundary, when skeletal fauna appeared, and carbonate accumulation became largely biogenic. Along with the basins of the continental block, there were new oceanic areas of formation of carbonate sediments, where the skeletons of nekton organisms became a significant supplier of material. The fourth boundary – Paleozoic-Mesozoic one – was the beginning of the accumulation of the proper oceanic deep-water carbonate sediments. The fifth milestone is associated with the Cretaceous period, when oceanic carbonate accumulation sharply increased due to planktonic organisms.

Application of geological geomorphological and geochronological (¹⁴C, OSL) methods allowed to establish that the bordering mountains of the Chuya basin (Russian Altai) were affected by glaciation already in the Middle Pleistocene – about 160–180 ka ago (MIS 6). However, the maximal ice-dammed lake with the highest (up to 2100 m a.s.l.) strandlines both in the Chuya and Kurai basins existed later than 90–80 ka ago, in the Late Pleistocene. This chronological benchmark limits the influence of the cataclysmic outburst floods from the largest ice-dammed lakes on the accumulation of the Inya formation in the Chuya and Katun river valleys. It is confirmed that a large ice-dammed lake existed and had a water level of at least 1730 m a.s.l. in MIS 2 in the Kurai basin. It was drained no later than 16 ka ago. Synchronously (about 17–16 ka ago) the accumulation of diluvial-lacustrine cyclites began in the Inya mouth. The Saldzhar formation had been depositing as a result of not only flood events, but also gradual hydrological processes in the Katun river valley between the mouths of the Chuya and Sema rivers during the entire MIS 2. It is necessary to revise the concept adopted by SibRISC in 2018. This concept assumes i) absence of ice-dammed lakes in intermountain basins of the Russian Altai in MIS 2 and ii) accumulation of the Inya and Saldzhar formations deposited by glacial megafloods in the valleys of the Chuya and Katun rivers before 90 ka ago.

Here we describe the first findings of frogs (Anura) from the Upper Cretaceous of Russia – the distal part of the humerus and the tibiofibula fragment. They come from the Maastrichtian dinosaur locality in the city of Blagoveshchensk in the Amur region. The described remains possess an outer and inner structure typical for Anura. These are the easternmost and the youngest frog remains from the Upper Cretaceous of Asia.

We test a new combined technique of solving nonlinear gravity problems using three types of datasets: gravity field, topography and crustal thickness in the Elysium Planitia region on Mars.

An analysis of variations in the microbaric background, magnetic and electric fields in the surface layer of the atmosphere, accompanying strong earthquakes on February 6, 2023 in Turkey, is presented. The analysis involved the results of instrumental observations performed at the Center for Geophysical Monitoring of Moscow and the Mikhnevo observatory of the IDG RAS, as well as data obtained by a number of magnetic observatories of the INTERNAGNET network. It is shown that, in addition to the seismic effect, earthquakes were accompanied by variations in the magnetic and electric fields, as well as the generation of infrasonic waves recorded at a considerable distance from the sources.

The climate changes taking place in the Arctic are expressed in the increase in extreme values, as well as in a wide range of processes of degradation of permafrost, the state of which, being sensitive to climate change, causes the activation of rapidly proceeding exogenous processes. To predict the climate of the YaNAO for the middle of the 21st century, data from 42 models of the CMIP6 project were used. The temperature in January will increase by about 3.5 (on the coast of the Kara Sea even by 4.5°C), and in July by ~2.5°C everywhere. The 5 and 95% quantiles will increase by 3 and 4.5°С in January and by 2 and 3°С in July, respectively. Monthly precipitation will increase by an average of 10% in January and remain unchanged in July. The 95% quantile values will increase by 30% and 10% in January and July, respectively. The number of days with frost will be reduced. Warming in combination with an increase in precipitation will lead to an increase in the activity of avalanches, snow flows and mudflows on the eastern slopes of the Urals, as well as on the characteristics of landslides, abrasion, suffusion, erosion, thermokarst, and solifluction. Climate-dependent sectors of the economy should be ready for predictable changes in the natural environment.

Organic compounds: C_org, lipids, hydrocarbons (HCs) – aliphatic (AHCs) and polycyclic aromatic (PAHs) in suspended particulate matter of surface waters and in bottom sediments of the shallow Chernavka River, which flows into a self-sustaining Elton Lake were studied. High concentrations of organic compounds were found in surface waters: in averaged 692, 80 and 0.79 µg/L for lipids, AHCs, and PAHs respectively. The composition of alkanes in the aqueous suspension corresponded to the weathered oil hydrocarbons. HC transformation occurs here not in the course of sedimentation, but at the water–bottom sediment interface. As a result, the AHC composition of the sediments differed from that of the particulate matter in the presence of planktonogenic low molecular weight homologues of n C₁₅–C₁₇ and a sharp increase in the series of odd high molecular weight alkanes, while the PAH composition differed in the increase in the proportion of naphthalene.

Studies on the environmental assessment of Pb content in agroecosystems were carried out in the forest-steppe zone of the Belgorod region, which is located in the south-west of the Central Black Earth region. The soil cover was represented mainly by leached chernozems. As a result of studies, it was established that in the layer of 0–20 cm of arable soils, the average gross content of Pb is 13.1, the concentration of mobile forms is 1.09 mg/kg, which does not exceed the background values and is significantly lower than the levels of APC and MAC. There were no significant differences in the content of Pb in the soil layers of 0–20 and 21–40 centimeters. The excess of background concentrations of this element is established in the soils of roadside ecosystems. The main source of Pb supply to the agroecosystems of the Belgorod region is organic fertilizers, but this does not pose a danger to soil pollution and crop production. The average Pb content of corn, barley and winter wheat grains did not differ significantly and was 0.267, 0.275, 0.292 mg/kg, respectively. Of the studied cultures, the minimum amount of this element was contained in soybean grains (0.155 mg/kg), and the maximum amount in sunflower seeds (0.335 mg/kg). Of perennial legumes, the minimum amount of Pb was contained in clover hay (0.185 mg/kg), and the maximum amount was esparceta (0.344 mg/kg). Exceeding the levels of the maximum permissible concentration and the maximum permissible level of Pb in crop production was not detected.