Volume 515, Nº 1 (2024)

The capabilities of discovering large oil fields in the central part of the Yenisei-Khatanga regional trough were considered. Processing and integrated interpretation of geological, geophysical and geochemical information provided the basis for the identification of four promising oil accumulation zones (an area of 58 thousand km²). For the multi-deposit Payakha oil field, three more zones located at depths of 3.2– 3.5 km were identified at the base of the clinoform complex. This made it possible to ensure the increment of localized recoverable oil resources of D₁l category.

The Early Permian (275.3 ± 3.1 Ma) ⁴⁰Ar/³⁹Ar plateau age of detrital mica (Cr-phengite) from clasts in listvenite sandstones of the ophiolite-derived clastic sequence of the Rassokha Terrane of the Chersky Range probably corresponds (or is close) to the time of the formation of listvenites of the provenance (ophiolitic massifs of the range) and restricts the maximum deposition age of clastic rocks. A partial loss of Ar by mica as a result of deformations and postsedimentation transformation of rocks of the ophiolite-derived clastic sequence in the Early Permian is possible but it is less probable.

The Stratigraphic Drilling Project of the Russian Arctic Shelf conducted by the PJSC Rosneft is aimed at discover the stratigraphic age and rock composition of sedimentary succession of its subsurface. In 2021, six shallow wells for the first time have been drilled with core sampling in the east of the Laptev Sea. Drilling revealed folded sedimentary succession dated back to the Late Barremian – Early Aptian. The synrift complex overlying unconformably dates to the Paleocene. The upper strata dates from Eocene to Pleistocene and contains significant hiatuses. The data discovered together with the results of seismic interpretation clarified the regional geological model and dated the stages of its tectonic evolution.

To gain insight into the source of ore material, this study presents the first Re-Os and Pt-Os isotopic and highly siderophile element (HSE) abundance data for chromitite and osmium minerals from the Guli massif of ultramafic, alkaline rocks and carbonatites located in the Maimecha-Kotui province, Polar Siberia. The study utilized a number of analytical techniques, including electron microprobe analysis, negative thermal ionization mass spectrometry (N-TIMS) and high pressure asher digestion and an isotope dilution-inductively coupled plasma-mass spectrometry. The HSE concentrations in chromitite samples range from 191 to 866 ppb with a predominance of Ir-group platinum-group elements (PGE) (Os, Ir and Ru) over Pt-group PGE (Rh, Pt and Pd) and Re, which is consistent with their platinum-group mineral control (i. e., Os-Ir alloys and laurite, RuS₂) within the chromitite. The Re-Os and Pt-Os isotope data indicate that the HSE budget of the chromitite and osmium minerals from the Guli massif was largely controlled by that of the mantle source, which evolved with long-term near-chondritic Re/Os and Pt/Os ratios; this source is within the range of those for the majority of komatiite and abyssal peridotite sources.

For the first time, concentrations of gases ¹²CO₂,¹³CO₂, СН₄, Н₂О and the dynamics of Earth degassing under the changing atmospheric pressure were remotely analyzed using a differential absorption lidar. To reduce the influence of external meteorological factors, the sensing was carried out in a dead-end tunnel of the Baksan Neutrino Observatory of the Institute for Nuclear Research of the Russian Academy of Sciences.

Isotope-geochemical (δ²H and δ¹⁸O in H²O, δ¹⁵N in N₂, δ¹³C in CO₂ and CH₄,³He/⁴He) studies of СО₂-rich thermal waters (up to 41.3^oC) which located in 4 km long tonnel of the Baksan Neutrino Observatory were carried out. The δ¹³C(CO₂) values (–8.0… –6.4‰) indicate the volcanogenic genesis of CO₂. The presence of the volcanogenic component is also emphasized by high values of ³He/⁴He (346 × 10^–8). At the same time, nitrogen present in the gas phase is characterized by values of δ¹⁵N = +1.3‰, indicating its crustal genesis. In the tunnel, an elevated concentration of CH₄ (up to 0.5%) was noted in one of the gas outlets. This methane is characterized by high δ¹³C values (–33.5 and –26.0‰), which, in general, are typical for other СО₂-rich springs of the Eastern Elbrus Mountains. In contrast with the other CO2-rich springs of the North Caucasus, which are practically indistinguishable from surface waters in terms of δ²H and δ¹⁸O values, the CO₂-rich thermal springs of the tunnel are noticeably enriched in heavy oxygen isotope (¹⁸O). This is a consequence of oxygen exchange between the waters and the host rocks at elevated temperatures. In the δ¹⁸O-δ²H diagram, the figurative points of thermal waters form a trend that reflects the mixing of isotope-light infiltration waters with isotope-heavy waters.

Petrography, geochemistry and isotope geochemistry of the Mesoproterozoic volcanic rocks occurred as lava flows and the Valaam sill in the Ladoga rift, have been studied. The Ladoga rift is located in the area of thrusting of the Palaeoproterozoic Svekofennian orogenic complexes onto the Archean Karelian craton. Ferrobasites of close composition and geological position in lava flows and sill have different Nd isotopic composition, differing by 5 units εNd(t): –4…-5 in ferrobasalts of lava flows and a very low-radiogenic Nd isotopic composition in mafic rocks of the sill (εNd(t) to –11 for ferrogabbro), and identical to the isotopic composition of its acidic rocks (εNd(t) to –11 for granophyres). It is shown that in the crust, heterogeneous in age, the process of fractional crystallisation along the tholeiitic trend combined with assimilation of melt from wall rocks can be an effective mechanism for forming such “paradoxical” features of the Nd isotopic composition. The isotopic composition of sill rocks indicates the probable presence of Mesoarchean blocks in the lower crust of the Ladoga graben region.

Seismicity modeling is an important part of creating General Seismic Zoning maps within the framework of a probabilistic approach. We consider the main disadvantages of individual elements of the recent seismicity models. A variant of the methodology is proposed, which, due to the improvements of those elements, should provide more accurate estimates of the future seismicity. For the first time, a stochastic seismicity model has been proposed in the form of a synthetic earthquake catalog, generated for an arbitrary conditional period and reproducing the properties of the catalog of actual earthquakes, including spatiotemporal grouping. A methodology for verifying seismicity models is proposed to check the compliance of the models with the initial data, to assess the predictive efficiency of the models, and to compare efficiency of different models.

The geophysical effects of a strong seismic event in the form of two earthquakes of magnitude 6.8 and 4.9 that occurred on September 08, 2023 in Morocco at close times 22:11 and 22:30 UTC with an epicentral distance between the foci of ~ 4 km are considered. We used data from a number of observatories of the INTERMAGNET network and the results of magnetic registration at the Mikhnevo Geophysical Observatory of IDG RAS. It was shown that in the absence of significant global disturbances of the Earth’s magnetic field, earthquakes were accompanied by a series of three positive bay-shaped geomagnetic variations with maximum amplitudes from ~1 to ~10 nT, following each other after ~60 min. The maxima of the induced magnetic field variations were observed almost synchronously at distances from ~800 to ~10000 km. The delay time of the magnetic effect relative to the main shock of the first earthquake was ~70 min. Taking into account the almost planetary nature and high synchronicity of the magnetic field disturbances caused over a significant range of distances, as well as time delays corresponding in order of magnitude to the travel time of the seismic signal of a distance multiple of the size of the Earth, it is suggested that the magnetic effect of the seismic event in question was caused by a global source, which can serve as an excited geodynamo. The ionospheric effect of the seismic event under consideration is presented in the form of variations of the critical frequency f₀F2 calculated from the data of the ground-based sounding station of the del Ebre Observatory.

Based on fluctuations measurement results in the components of wind speed, air temperature and concentration of aerosol particles on a desertified area in the Astrakhan region under conditions of intermittent emission of dust aerosol, vertical turbulent fluxes of dust aerosol and heat were determined. Using spectral analysis, the temporal variability of the horizontal and vertical components of wind speed, air temperature and concentration of dust aerosol particles was characterized. It is shown that the intermittent emission of the dust aerosol is determined by low-frequency convective-induced variations in the horizontal component of wind speed when the threshold saltation speed is exceeded. Significant differences in the spatiotemporal variability of vertical heat transfer and dust aerosol were revealed. The 30-minute average values of heat fluxes (90–158 W/m²) and dust aerosol (7.2–27.5 cm^–2cm^–1), as well as the rate of heat removal (14–21 cm/s) and dust aerosol (10–16 cm/s).

Soils play an important role in maintaining the sustainability of the biosphere, as well as providing food, clothing and the basis for human life on Earth. In the process of irrational land use, soils are often degraded and sometimes completely destroyed. But, inventory of destroyed soils on a systematic basis is still not conducted in any country of the world. In Russia, traditional soil maps do not reflect the destroyed soils either. We have made an attempt to create the first map of the country, which shows soils destroyed as a result of directed anthropogenic impact. The map shows areas where soil cover was destroyed as a result of construction of buildings, structures, roads and railroads, quarries and embankments during mining. The crowdsourcing database OpenStreetMap was used as the main source of information, as well as the results of visual interpretation of disturbed soils using GoogleEarth^TM satellite data. The data on disturbed soils were aggregated to soil-geographical sections of the Unified State Register of Soil Resources of Russia (scale 1 : 2500000) (UGRSR). The map is presented in GIS format (shapefile). The map contains information on the area and share of disturbed soils, as well as the type of impact that resulted in disturbance.

Patterns of distribution of rare earth elements (REE) in natural objects are important geochemical indicators of the state of the environment. For the first time, data on REE contents in fucus algae from various horizons of the littoral of the Barents Sea are presented. The behavior of REE in natural processes is controlled by the solubility of their compounds, the ability to complex, and the tetrad effect of fractionation. Natural factors determining REE migration in the sediment–water–macrophytes system are discussed.

An analysis of the problem of water bodies eutrophication as a global process is presented. The volumes increasing use of nitrogen and phosphorus on a planetary scale are shown, the dispersion of which leads to an increase in the content of nutrients in lakes and rivers. The results of original studies of remote lakes in the Arctic zone are presented, which showed an increase in the concentrations of nutrients in lakes in recent decades. A tendency has been revealed for an increase in the contents of nitrogen and phosphorus, as well as organic matter in lake waters, even in the absence of anthropogenic influence. It has been established that an increase in temperature and climate warming in the Arctic regions exert the main influence on the increase in the content of nutrients and the trophic status of lakes.

High subglacial heat flow and volcanic activity in West Antarctica contribute to instability and accelerated flow into the ocean of the West Antarctic ice sheet. In this case, a catastrophic rise in sea level by tens of centimeters – the first meters can occur in a very short geological time (years-decades) due to the rapid sliding of large masses of ice in West Antarctica into the ocean. If the Pine Island (50 cm sea level rise) or Thwaites (65 cm sea level rise) glaciers slide into the ocean, the West Antarctic Ice Sheet will lose support from these glaciers and may begin to collapse. In this case, the sea level will rise by a few meters. Based on Glen’s rheological law for a two-dimensional model of the movement of ice as a nonlinear viscous fluid, the flow velocities of a 3000 m thick glacier were calculated under conditions of adhesion to the bed (~20 m/year) and under conditions of sliding along the bedrock when the lower edge of the glacier melts due to increased heat flow from below (~3000 m/year). These velocities are in good agreement with the velocities of the Pine Island, Thwaites, Amery, Denman and Totten glaciers. The rapid movement of some outlet glaciers in East Antarctica is also likely caused by melting of their bases, suggesting increased subglacial heat flow in these areas of East Antarctica.

The study investigates the potential hazard arising from the actions taken by the Japanese government regarding the discharge of technical radioactive water from the Fukushima-1 nuclear power plant storage facilities. The contamination of the South Kuril Fishing Zone (SKFZ), which is one of the most promising fishing areas for the Russian Federation, with radioactive particles, is considered. Based on the modeling of passive markers simulating radioactive contamination, the study analyzes the pathways and mechanisms of pollution transfer into the SKFZ. The research is conducted using altimetric data on geostrophic currents for the period from August 24, 2022, to August 24, 2023. The pollution transfer into the SKFZ is determined by a set of conditions related to the current development regime of the First Kuril Meander and the local vortex system with varying characteristics, both near the discharge site and at the SKFZ border. A seasonal dependence of the speed and quantity of polluted water infiltration toward the Russian Federation’s shores is established. The possibility of rapid pollution advection into the SKFZ within 13 days has been discovered. This speed is due to the entrainment of contamination by the Kuril Meander and its further transport by the mesoscale vortex system to the SKFZ border. The study reveals periodicity in the influx of pollution into the SKFZ. Graphs depicting the distribution of the quantity of “dirty” markers over their release times and the arrival of polluted water at the SKFZ border have been created.