Vol 518, No 2 (2024)

A unique feature of the Kamchatka Peninsula is the Central Kamchatka Depression (CKD) stretching 400 km along the peninsula. Existing geodynamic models connect the formation of the CKD with the extension of the East Kamchatka toward the Pacific Ocean due to the slab rollback. However, no radiometric ages of the CKD formation have known yet, thus making it impossible to directly link the emergence of the CKD to the stages of Kamchatka tectonic evolution of and to the recent tectonic deformations. The paper presents the results of XRF analysis and K-Ar dating of lavas from the Kl-1 borehole near the Klyuchi settlement. Samples from the depth interval of 50–475 m (ages 0.72 ± 0.05, 1.54 ± 0.15 and 1.46 ± 0.08 M a) correspond to medium-K basalts and high-K trachyandesibasalts, likely similar to the rocks exposed at the base of the Kliuchevskaia Group. Still, these studied rocks are much older than any other dated rocks of the Kliuchevskaia Group (dates does not exceed 0.3 Ma). Below the stratigraphic unconformity at a depth of 905 m, a single date of 3.5 ± 0.4 Ma was obtained, which coincide with the end of accretion of the Eastern Peninsulas, which caused the transverse compression across the peninsula. Thus, the time of CDD emergence likely falls within the range of 1.5–3.5 Ma.

The results of systematic K–Ar geochronological studies are presented for the rocks of the Late Cenozoic basaltic Dariganga Volcanic Field (DVF). Four stages of its volcanic history have been identified: Middle-Late Miocene (>10 Ma), Late Miocene-Early Pliocene (7.8–3.5 Ma), Late Pliocene (2.8–2.6 Ma) and Pleistocene (<1.7 Ma). The volcanic products of each stage were suitably distributed over the area of the volcanic field. The main volume of volcanics was erupted during the Late Miocene–Early Pliocene and the Pleistocene. During the Late Miocene–Early Pliocene, the northwestern part of the lava field was formed, which has a lava plateau morphology. Eruption centres were located within structural depressions that developed during extension and accompanied volcanism. The south-eastern part of the DVF was formed during the Pleistocene. Volcanism occurred simultaneously with the uplift of the Khukhot-Ein-Nuruu ridge within the Nukut-Daban highland, which influenced the morphology of the volcanic cover. This volcanic stage is characterised by large multi-centre shield volcanoes localised in the axial zone of the ridge, and extensive valley lava flows spreading down both slopes of the ridge. The volcanic history of the DVF and other volcanic areas of the Late Cenozoic intraplate volcanic province of Central and East Asia are compared. They developed in concert with each other, so the formation of the DVF being initiated by the same geodynamic mechanisms as the other volcanic areas of the province, namely the activity of a small mantle plume.

For the first time in the North-East of Russia, changes in the values of δ¹³С_оrg in the lower part of the Permian were detected, obtained in the Kubalakh section of the lower reaches of the Lena River and integrated with biostratigraphic data. A comparison with isotope-carbon trends identified in the Asselian and Sakmarian of the Southern Urals is proposed. Based on the established sequence of negative shifts of the carbon isotopic composition of organic matter, it is concluded that the boundary of Carboniferous and Permian in the Kubalakh section is located below the beds opened in the section and there is an 80 m break in the outcrop. The first data independent of biostratigraphic and paleontological constructions have been obtained on the Late Asselian age of the Tuora-Sis Formation containing the ammonoid association with Bulunites, the stage belonging of which has been debated for many decades. The chronostratigraphic indefinite interval between the Asselian and Samarian to the upper parts of the Jakutoproductus lenensis Beds has been significantly reduced. The data obtained indicate that the continuation of work on the chemostratigraphy of stable carbon isotopes has good prospects for substantiating the stage division and interregional correlation of the Lower Permian deposits in the Verkhoyanie.

For the first time, Sr chemostratigraphic characteristics of marine sediments of the Lower Permian of the Omolon massif of Northeast Asia have been obtained based on the study of well-preserved brachiopod shells. The ⁸⁷Sr/⁸⁶Sr ratio in brachiopods from the Lower Permian regional horizons (regional stages) is within the following range: Orochian – 0.70786–0.70794, Ogonerian – 0.70744– 0.70786, Koargychanian – 0.70745–0.70748, Khalalian – 0.70742–0.70735. The obtained Sr isotope data demonstrate good agreement with the standard variation curve of the ⁸⁷Sr/⁸⁶Sr ratio in the Permian Ocean. New Sr isotope data can be used to directly correlate units of the Regional Stratigraphic Scale of Northeast Russia with the stages of the International Permian Stratigraphic Scale. Based on new data, the Asselian age of the Orochian regional stage of the lower part of the Permian section of the Omolon massif has been proven, and the regional correlation of the Upper Sakmarian interval, previously established from biostratigraphic data, has been clarified.

The paper presents first data on isotopic U-Pb study (LA-ICP-MS method) of zircon from intrusive rocks of the Kensu pluton situated in the eastern part of the deep-seated fault system of the “Nikolaev Line”. This pluton of high-potassic (shoshonitic series) rocks is accompanied by the Kensu deposit and other occurrences of skarn and porphyry W-Mo-Cu-Au mineralization. Together with the other Au, W and Cu deposits and occurrences, they are parts of the extended metallogenic belt of Tien Shan. The concordant isotopic U-Pb age data for zircon autocrysts from the rocks of the consecutive intrusive phases span over the interval of approximately 325 to 302 Ma. This interval comprised the crystallization of monzogabbro (321 ± 4 Ma), monzonite (319 ± 4 Ma), camptonite (306 ± 4 Ma), syenite (307 ± 6 Ma), quartz syenite (305.5 ± 2 Ma), and quartz monzonite (305 ± 3 Ma). Zircon antecrysts dated at 316–325 Ma to 335–345 Ma have also been identified. The age data obtained are consistent with the age of subduction processes defined for the western part of the Middle Tien Shan. However, both geochemical characteristics of the rocks from the Kensu pluton and a distinct W-Mo mineralization related to this pluton contradict the subduction-related setting of the pluton emplacement but, instead, point out the post-collisional setting of the intrusion emplacement. This discrepancy can be explained by a “scissor-like” (from east to west) closure of the Turkestan paleoocean that has resulted in the post-collisional regime in the eastern part of the “Nikolaev Line”, whereas subduction continued in its western part. The rocks also contain zircon xenocrysts with a much older age (in to order of 1.9 Gb) that probably represents the age of the Tarim craton basement rocks; this indicates an involvement of the ancient material in the magma generation.

We studied the isotopic composition and helium and neon ratios of fluid inclusions in magnetite and pyrite from carbonatite breccias of the Sallanlatva alkaline-ultrabasic complex using the stepcrushing method. The results indicate a high probability that fluids from several sources, captured in different proportions, were involved in the formation of the Sallanlatva explosive carbonatite breccias. The R/Ra ratio (R is the measured ³He/⁴He ratio, and Ra = 1.382 x 10^-6 is the same ratio in atmospheric air) reaches a value of 2.3, which is a reliable indicator of mantle gas involvement. The low (1 to 44) value of the ⁴He/²⁰Ne ratio suggests the contribution of atmospheric gases dissolved in paleometeoric waters. The combination of these two facts supports the hypothesis of the phreatomagmatic nature of the studied breccias, i.e. their formation due to the interaction of infiltrated high-temperature orthomagmatic fluid with meteoric waters transporting dissolved atmospheric gases.

Tetrahedrite-(Cd), with the ideal formula Cu₁₀Cd₂Sb₄S₁₃, is a member of the tetrahedrite series of the tetrahedrite group with a predominance of Cd at the C position typically occupied by divalent metals. Cadmium end-members from the tetrahedrite group are rare: they were found in 15 deposits and ore occurrences. The article reports on a new discovery site of Ag-bearing tetrahedrite-(Cd) at the Kon-Dara mineral deposit (Southwestern Pamirs, Tajikistan) and summarizes the known data on rare Cd-bearing fahlores with Cd content from 1 to 12.31 wt. %. Ag-bearing tetrahedrite-(Cd) at the Kon-Dara deposit occurs as xenomorphic segregations 10–35 µm in size in association with tetrahedrite-(Fe), tetrahedrite(Zn), galena, polybasite, and chalcopyrite, which replace bournonite. According to the EPMA data, its composition averaged over seven analyzes (in wt. %) is as follow: Ag 16.17, Cu 25.19, Cd 10.09, Fe 0.38, Zn 0.09, Pb 0.13, Sb 25.55, As 0.18, S 22.34. The empirical formula calculated based on 29 atoms per the unit is (Cu_7.40Ag_2.80)_Σ10.20(Cd_1.68Fe_0.13Zn_0.03Pb_0.01)_Σ1.84(Sb_3.92As_0.04)_Σ3.96S_13.00. The composition of the tetrahedrite-(Cd) from Kon-Dara is similar to those from the Tyndrum Pb-Zn mineralization in Scotland, the Clara baryte-fluorite-(Ag,Cu) mine in Germany, and the Xaitishan Pb-Zn deposit in China. The formation temperature of Ag-bearing tetrahedrite-(Cd) at the Kon-Dara deposit is estimated to has been at about (170-140) ± 20°C.

Palynological analysis of Paleogene and Neogene strata in the south of Western Siberia (BH. 2, Novosibirsk Oblast) showed that a part of the conifer bisaccate pollen in the spore-pollen spectra has a number of morphological characteristics that allow it to be compared with the pollen of modern Cathaya argyrophylla Chun et Kuang. These palynomorphs belong to relict vegetation currently developed in the humid subtropical climate of southern China and are an important climatic indicator. Palynomorphs are assigned to the ancestral forms of Cathaya – to the species Abietineaepollenites sellowiiformis (Zaklinskaja) Doweld 2018. A description of the pollen is given, its distribution along the section is shown. The maximum amount of A. sellowiiformis pollen (up to 23.7%) is confined to the upper Oligocene and lower Miocene, the last appearance was recorded in the middle-upper Miocene. The data obtained expand our understanding of the geographic range of the ancestral form of Cathaya and its role in the plant communities of Central Asia in the Cenozoic.

Based on Sentinel-1A satellite images acquired between 01.05 and 22.09.2023, the differential interferometry method (DInSAR) calculated successive displacement fields in time, which clearly show a dome-shaped uplift on the western slope of the Shiveluch volcano, 8–8.5 km west of its active crater. Uplift was especially intense at the satellite acquisition intervals 01.05–13.05.2023, 13.05–25.05.2023 and 25.05–06.06.2023. To test the hypothesis about formation of a displacement area due to magma injection under the western slope of the volcano, numerical modelling was carried out and parameters of magmatic body like a sill were determined, which forms the displacements on the surface that best match the displacement observed from satellite radar interferometry data. It is assumed that after the eruption on 11.04.2023 magma rose from a depth of 20–25 km through a fissure formed under the western slope of the volcano and penetrated horizontally under the slope at a depth of 1–2 km in the north-northwest direction. Within the precision of data on slope displacements, the size of the magma body varies from 6.0 х 3.0 km at 1 km depth, to 5.25 x 1.4 km at 2 km depth, while its height ranges from 0.5 to 1.75 m and its volume from 0.009 to 0.0129 km³. Thus, based on radar interferometry data in combination with the data on the distribution of seismic activity accompanying the magma movement, the model of the magmatic body that penetrated under the western slope of Shiveluch volcano in the postparoxysmal phase of the eruption on 11.04.2023 was constructed. The Formation of a new extrusive dome on the western slope of Shiveluch volcano at the end of April 2024 confirms the hypothesis about injection of magmatic material under the western slope of the volcano and allows to estimate the rate of magma rise to the surface.

Based on the analysis of data from the Mikhnevo geophysical observatory of the IDG RAS and a number of observatories of the international INTERMAGNET network, the disturbances of the geomagnetic field in the surface atmosphere were considered during a series of strong earthquakes that occurred on April 02–03, 2024 in the vicinity of the island of Taiwan. It is shown that in the absence of significant global disturbances of the Earth’s magnetic field, earthquakes were accompanied by geomagnetic variations with a maximum amplitude of ∼10 nT and a total duration of about 4 hours. The delay time of the magnetic effect relative to the main shock of the first earthquake was ∼60 minutes. Based on the results of processing ionograms of height-frequency sounding obtained at the Okinawa ionospheric monitoring station and freely available on the website of the Japan National Institute of Information and Communication Technologies, the ionospheric effect of the event in question was established in the form of variations in the critical frequency of the F2 layer of the ionosphere.

Pioneer results of high-precision direct determination of CO₂ in the surface waters of the Black Sea have been presented in this paper. This data has made possible high precision characteristics of the content and intra-annual variations of CO₂. The average annual value of pCO₂ is 436 µatm, which is higher than the average annual value of the near sea surface atmosphere (420 µatm). The analysis of seasonal variability has revealed about 30% decrease in sea water pCO₂ from late spring to autumn. The minimum values of pCO₂ are detected in January – February, the maximum ones in July. Seasonal variations in the CO₂ content in the near sea surface atmosphere have revealed an inverse relationship – with maximum values in February and minimum values in July. This indicates different mechanisms of the CO₂ evolution in the air and seawater. Seasonal variations in the intensity of burning organic carbon, as external sources, influence the content of CO₂ in the atmosphere. Variations in temperature and the state of the carbonate system, as abiotic factors, govern pCO₂ in water. In the summer-to-autumn period, pCO₂ is governed by a combination of abiotic and biotic factors – variations in temperature and intensity of production and transformation of organic matter. The ratio of abiotic to biotic factors varies from season to season, but abiotic factors remain primary throughout the year.

The study of herbarium materials of the Ephedra dahurica Turcz. collected in the Torey Lakes region in different years, revealed the morphological variability of its pollen grains. An inverse relationship has been established between the development of the number of furrows and ribs of pollen grains and the values of temperature and humidity during the growing season. During wet seasons, the plant produces pollen grains with few furrows. The number of furrows increases during dry and cool growing seasons.

The article presents the biochemical composition of sapropels from Lake Small Simagen, studied using modern methods of atomic emission spectrometry (ICP-AE) and high-performance liquid chromatography (HPLC). This source of organic matter is now the least in demand in the country; many deposits are abandoned. However, such organic colloids and their humic extracts are not inferior in their spectrum of action to extracts from peat or coal. The study showed the predominance of the proportion of potassium and sodium in the gross composition of macroelements. Among microelements, both in bulk and in mobile forms, iron and manganese ions dominated. Apparently, the Fe cation is bound in polyligand forms with carboxylic acids. The ratio of these two elements in the samples averaged 10:1 – Fe:Mn. The content of heavy metals was within the limits acceptable for sapropel fertilizers according to GOST R 54000–2010. The results obtained during the study can be further used in the biotechnology of intensive crop production, when growing crops in a hydroponic environment while minimizing the use of synthetic fertilizers. In addition, since carbohydrates were found in all studied samples of these raw materials, the extracts can be used in the development of modified nutrient media in the field of agricultural microbiology to stabilize the titer of beneficial rhizobacteria.

For the first time, the content of 17 individual PAHs was analyzed in samples of background and urban soils obtained during a geochemical survey of the territory of Ulan-Ude in the summer of 2022. The average content of PAHs in the urban soils is 801 ng/g, which is more than 8.5 times higher than the level in background chestnut soils. The soil cover is contaminated predominantly with mediumand highmolecular-weight polyarenes. The share of individual PAHs in the soils of Ulan-Ude ranges within 4–11% with an average value of 6%. In the urban soil cover, ten high-contrast anomalies were identified with the amount of PAHs ranging from 3162 to 10189 ng/g. The principal component analysis and indicator ratios of polyarenes made it possible to identify the main types of sources and their contribution to urban soil pollution.