Home – Home – Jornals – Advanced Search

The study focuses on determining the position of the southern boundary of the Okhotsk Plate based on the analysis of seismicity distribution in the Hokkaido and Honshu regions as well as adjacent territories according to the Japan Meteorological Agency (JMA) data for a period of 1998-2022. The seismicity distribution data are compared with regional seismic tomography models and the distributions of the directions of principal seismotectonic deformation axes according to data on the focal mechanisms of strong ( M_w > 4.7) earthquakes using the International Seismological Center (ISC) data for a period of 1976-2022 and other recent geological-geophysical characteristics, such as gravity field heterogeneities, crustal thickness, volcanic manifestations, etc. It is revealed that the southern boundary of the Okhotsk Plate actually passes along the southern tip of Hokkaido Island (through the Oshima Peninsula and Uchiura Bay) rather than along the Hidaka Ridge or through Honshu Island, as previously assumed by other authors.

We discuss possibilities of application of radon activity concentration variations in investigating changes in the stress-strain state of a rock massif. Based on the long-term radon monitoring at the South Kuril geodynamic polygon, the methodology for interpretation of soil radon activity concentration anomalies has been developed. A causal relationship between earthquakes and radon anomalies has been established. It is shown that tectonic events occur after the radon anomaly passes over the maximum level, and the reflection time depends on the distance between the observation point and the epicenter of the event. The mechanisms of formation of radon anomalies in the compression/extension zones are described.

The stored waste from processing Ni-Co arsenide ores of the Khovu-Aksy deposit (Republic of Tyva, Russia) is a unique geochemical system, in which the joint behavior of As and metals (Fe, Co, Ni, Cu, Zn, and Pb) under exogenous conditions can be directly traced. We have studied the mineralogical and geochemical specifics of the distribution of arsenic (from primary arsenides to newly formed phases) and associated metals in waste with a high As content (up to 4%) throughout the section of trench burial No. 3. These strata are characterized by a slightly alkaline environment with pH = 7.7 and Eh = 486 mV. Four horizons are distinguished in the section. According to elemental analysis (XRF-SR), As, Mo, Pb, Sb, Co, and Cu accumulate in horizon 2 (80 cm), whereas Cd, Zn, and Ni, in horizon 3 (110 cm). In the processed ores, nonmetallic (rock-forming) minerals are represented by quartz, calcite, dolomite, garnet, amphibole-chlorite aggregates, single grains of K-feldspar (Kfs), apatite, barite, and muscovite. Arsenic minerals are distributed extremely unevenly throughout the section and are absent from the soil horizon (horizon 4). Arsenic is found in the section as: (1) arsenic minerals, namely, safflorite with hovuaksite, conichalcite, scorodite, arseniosiderite, sarmientite, hörnesite, annabergite, and picropharmacolite; (2) isomorphic impurity in secondary products (iron hydroxides developed after pyrite, amorphous silica, and chlorite). The presence of carbonate minerals in primary ores and the applied technological scheme of ore dressing with purification of solutions from arsenic affect directly the secondary assemblage of arsenic minerals.

Experimental studies on modeling the diamond resorption processes during mantle metasomatism accompanied by oxidation process in solid-phase matrix in the presence of intergranular fluid have been carried out. The reaction conducted between diamond and periclase to form magnesite can be considered as prototype EMOD (enstatite-magnesite/olivine-diamond) or DCDD (dolomite-coesite/diopside-diamond) reactions. The experimental studies were conducted at a pressure of 6.3 GPa in the 1100-1400 °C temperature range under redox conditions corresponding to the WM (wüstite/magnesite) buffer. It was found that the reaction between diamond and periclase to form magnesite occurs only in the presence of 0.5-0.8 wt.% water at temperatures above 1200 °C. The morphology of diamond crystals partially dissolved by intergranular H₂O-fluid at f _O2 at the WM buffer level represents a typomorphic feature of diamond dissolution/resorption in water-containing carbonate and carbonate-silicate melts. The main microrelief elements of diamond dissolution forms are negatively orientated triangular etch pits on relict octahedral faces, shield-shaped or ditrigonal dissolution layers, and drop-shape hillocks. The obtained resorption rates at these P-T- f _O2 parameters indicate that the absence of diamond in kimberlites or low-grade potentially diamondiferous kimberlite pipes might be caused by oxidizing metasomatic events in the lithospheric mantle in the regions of kimberlite emplacement.

A synthetic analog of mourite (SM), (UO₂)Mo₅O₁₄(OH)₄(H₂O)₂, has been hydrothermally synthesized at 220 ºС and characterized using single-crystal X-ray diffraction, single-crystal and powder X-ray diffraction studies at non-ambient temperatures, X-ray photoelectron spectroscopy, infrared spectroscopy, thermal, and chemical analyses. SM is monoclinic, P 2/ c , a = 9.9063(6), b = 7.1756(4), c = 12.2105(7) Å, β = 102.496(6)°, V = 847.41(9) ų; the crystal structure has been refined to R ₁ = 0.043. The chemical composition of the SM is (the Mo₂O₅:MoO₃ ratio obtained from X-ray photoelectron spectroscopy, H₂O by stoichiometry; wt.%): Mo₂O₅ = 4.61, MoO₃ = 61.06, UO₃ = 26.95, H₂O = 6.76, total 99.38. The empirical formula calculated on the basis of 22 oxygen atoms per formula unit with Mo^V + Mo^VI = 5 is (U^VI_1.03O₂)[(Mo^VI_4.63Mo^V_0.37)_Σ5.00O_13.81(OH)_0.19](OH)₄(H₂O)₂. The crystal structure of SM contains UO₈, Mo1O₆, Mo2O₅(H₂O), and Mo3O₄(OH)₂ polyhedra that share vertices and edges to form layers linked by hydrogen bonds only. SM is stable up to 250 ± 10 ºС. Upon heating, continuous dehydration occurs between 160-250 ºС until the formation of amorphous products; crystallization above 450 ºС produces UO₂MoO₄, MoO₃, and UMo₁₀O₃₂. Below 250 ºС, thermal expansion of the compound is strongly anisotropic, with the maximal direction perpendicular to the plane of the layers.

Studying the spatial distribution of specific groups of marine invertebrates in the geological past and analyzing their geographic differentiation over time are crucial for understanding both their evolutionary patterns and the history of marine basin development. This study, based on modern paleontological and biostratigraphic data of the Boreal Triassic, refines the taxonomic composition and distribution of Ladinian ammonoids across various regions of the Boreal Realm. Zonal correlation on ammonoids of Ladinian deposits has been carried out for Northeast Asia, British Columbia, the Canadian Arctic Archipelago, northern Greenland, Svalbard, and Franz Josef Land, providing a chronological basis for comparative analysis of coeval ammonoid faunas. The qualitative and quantitative comparative analysis of ammonoid assemblages for different phases of the Ladinian Age has established that Northeast Asia consistently belonged to the Siberian Province of the Boreal Realm. The separation of the Canadian Province of the Boreal Realm occurred at the end of the constantis Phase due to the penetration of trachyceratids (genus Protrachyceras ) into the paleobasins of the Canadian Arctic Archipelago. Subsequently, starting from the maclearni Phase, the area of the Canadian province expanded due to the migration of Tethyan forms into the paleobasins of Svalbard. The migrations of trachyceratids, gymnitids, and lobitids into boreal paleobasins from the Tethys Ocean, as well as the dispersal of Boreal tsvetkovitids and nathorstitids into ecotonal and Tethyan paleowaters of British Columbia, were influenced not only by circumpolar currents but likely, by the lifestyle of ammonoids and their adaptation to a broader or narrower range of marine basin depths.

The 29.07.2022 (UTC time 13:01:10.1) Tsagan-Shibetu earthquake with M_L = 6.2, M_W = 5.5 occurred in the eponymous mountain range in the eastern Altai Mountains (Gorny Altai), in proximity to the Tuva Basin (50.51º N, 90.69º E). The Tsagan-Shibetu Range was seismically inactive in the twentieth century, while neighboring with seismically active ones: the focal area of the 1970 Ureg-Nur earthquake with M_S = 7.0 and the seismically active Shapshal Range where earthquakes with magnitude of up to five occurred quite frequently, however, no large earthquakes have hitherto been reported. Significant alterations in the structure of seismicity of Gorny Altai occurred after the 2003 Chuya earthquake with M_S = 7.3: the period of quiescence was followed by emergence of new zones of enhanced seismic activity, with the Tsagan-Shibetu Range representing one of them. The internal structure of the mountain range is characterized by the formation of a triple-planed focal area with the pulse-like seismic process developing over time. The evolution of high seismicity in the considered mountain range occurred in the presence of foreshocks.

This paper presents the results of experiments to strengthen the surface of a fluoroplastic composite by creating a protective layer. The protective layer was formed by detonation spraying of VSNGN-85 powder consisting mainly of WC (81.56 wt.%) and Ni (10.6 wt.%). The granulometric and morphological properties of VSNGN-85 powder were studied, and its X-ray diffraction analysis was carried out. Optimal spraying modes for obtaining a dense coating 100÷115 mu thick were selected. X-ray diffraction analysis showed the presence of WO₃ tungsten oxide and NiWO₄(II) nickel tungstate in the coatings. The microhardness of the composite material with the protective coating was found to be 48 times higher than the microhardness of the composite without coating. The applied coating increases the life of the fluoroplastic composite, improves its strength, and slows down the processes of its oxidation, corrosion, and thermal destruction.

Fracture of the electrodes of a three-electrode pulsed X-ray tube with a rechargeable insulated electrode operating in explosive emission mode at a voltage of 600 kV and pulsed current up to 1000 A was investigated. The fracture was produced by the action of high pulsed electric fields and pulsed flows of electrons and plasma during vacuum breakdown in X-ray tubes. X-ray fluorescence microanalysis using a scanning microscope revealed the presence of numerous metal globules of size 10÷40 mu formed from both the tungsten anode material and the material of the third insulated Kovar electrode. Several stages of separation of the globules by the electric field were detected on the insulated electrode. Quantitative estimates for the critical values of Coulomb forces at which droplets arise were obtained in accordance with a dynamic model (taking into account the kinetic energy accumulated by the mass during the exposure to the electric field and surface energy), and the electric field pressures during the operation of the tube were estimated, allowing an explanation of the observed phenomena.

Results of experimental and numerical simulations of interaction of plane shock waves with gas-permeable cellular-porous targets are presented. Some of these targets are homogeneous over the thickness, while others consist of material layers with pores of different diameters. The experiments are performed in a shock tunnel in the range of the shock wave Mach numbers M=1,2÷1,8. High-porosity cellular nickel is chosen as a gas-permeable material. In numerical simulations, such cellular-porous materials are described by a toroidal model of a porous medium. The mechanism of formation of reflected shock waves is revealed. The intensity of waves reflected directly from the structural elements of the material and of waves reflected from the rear end face of the wind tunnel is shown to be lower in the presence of targets made of a gas-permeable high-porosity cellular material. The most effectively reflected waves are suppressed by combined targets composed of material layers with pores of different diameters.