Home – Home – Jornals – Advanced Search

The formation mechanisms of sedimentary basins are considered as a response of deep processes in the mantle, therefore they carry important information about the geodynamics and thermal regime of the lithosphere. For different sectors of the northern margin of the Siberian Platform, the dynamics of sedimentation and subsidence was reconstructed. The analysis of subsidence curves shows that during the late Paleozoic the sedimentary infill formed in the foreland basin environment. In the Late Permian-Early Triassic time, in the central and western sectors, the subsidence was accelerating due to the development of a thick trap complex; after the Permian and Triassic boundary the subsidence slowed down. During the period of trap magmatism, an anomalously high subsidence rate up to 4.8 km/ Myr in the central and up to 0.5-1.1 km/ Myr in the eastern and western parts was reconstructed. The high rate and short duration of accumulation of volcanogenic sediments can be explained by an episode of short-term extension under the influence of a plume, followed by a long period of thermal subsidence. Numerical modelling of the temperature regime near mafic intrusive bodies was carried out, which showed that when determining the paleoheat flow, the influence of trap intrusions can be traced up to 400-500 m from the contacts. Estimates of the paleoheat flow for the Permian-Triassic stage of tectonic evolution of the eastern sector were obtained. It was calibrated using the PetroMod software package, based on laboratory measurements of modern values of vitrinite reflectance for rock samples from wells, modern temperature and heat flow in the sedimentary cover. It was determined that trap magmatism occurred at temperatures increased to 100 mW/m², while the mantle component of the heat flow reached 38-72 mW/m²; it is several times higher as compared to modern one. The obtained paleoheat flow estimates for the Late Permian-Early Triassic stage appear to correspond to anomalously high values of modern continental rifts.

In 2019, employees of the Research and Production Enterprise Luch jointly with specialists of the Seismological Branch of the Geophysical Survey of the Russian Academy of Sciences (GS RAS) carried out river seismic exploration works using the common depth point method (CDP-2D) along a 170 km long profile in the lower reaches of the Vitim River. The research was carried out according to the original methodology developed in the Siberian branches of the GS RAS, using the Baikal instruments recording seismic signals continuously (in contrast to traditional cable bottom or ground-based systems with time-limited recording). In this case, patented Malysh air guns were used in the water for the excitation of elastic waves, which have been recorded by ground registration method on the riverbank. To this day, the archives store primary materials from each receiving point (about 7000, with a distance of 25 m between them) in the form of a continuous hours-long digital recording of seismic signals and noise. These materials make it possible to generate seismograms of significant duration - up to 23 s, equal to the time interval between wave generations, in contrast to 6-10 second seismograms traditionally used to construct sections of the upper part of the Earth’s crust. In addition, the 24-bit Baikal recorder makes it possible to record signals with an amplitude two orders of magnitude lower than the amplitude of seismic noise. On the seismic sections constructed by the processor at arrival times of up to 13-14 sec, due to an increase in the stack fold of signals up to 1000-2000, we can select low-amplitude waves, reflected from boundaries in the middle and lower parts of the Earth’s crust to the Moho boundary. High fold is achieved by increasing the size of the stacking site (bin) by several times. By processing seismograms, generated from archival materials, for the first time, we have a complete vertical section of the Earth’s crust along a 170 km long profile, using low-amplitude signals. The profile passes through the junction zone of the Angara-Lena monocline and the Bodaibo-Patom folded system. The proposed approach can be used to obtain preliminary (and relatively cheap) information about the deep structure of the Earth’s crust along profiles performed using the CDP-2D river seismic exploration method.

The paper presents theoretical results on mathematical modeling and numerical inversion of transient electromagnetic data for the monitoring of the state of the cryolithozone. Solutions to the direct and inverse problems are considered based on the vector finite element method, the Sumudu integral transform and the apparatus of artificial neural networks. We show the capability of spatial localization of thaw zones (taliks) with transient cross-borehole exploration systems in a geoelectric model that takes into account the dispersive properties of frozen rocks. The performance and accuracy of the developed algorithms are assessed.

This paper describes a technique for hierarchical neural networks based on the nearest neighbor method with preliminary clustering of the original training dataset and construction of a search cluster decision tree. This method is a promising alternative to neural network technologies with deep learning and has quite a few advantages: high learning rate, identification of objects with a low degree of similarity, and the ability to generalize and retrain. As shown by testing the hierarchical neural network method on real data from the West Siberian oil and gas province, predicting the oil saturation in the Vikulov suite interval is much faster and more efficient than inversion approaches to quantitative interpretation of seismic data while achieving fairly similar geological results. This characterizes the proposed method of hierarchical neural networks as an effective tool for the quantitative interpretation of seismic data to solve geological problems.

We report study results of basic intrusive bodies in the middle Paleozoic Vilyui paleorift (eastern Siberian Platform). Geochemical data for basic sills penetrated by boreholes in the rift’s dike swarms are presented, as well as our data on the time of formation of sills and dikes. We also studied mineral-hosted melt inclusions from a dolerite dike of the Vilyui-Markha dike swarm on the northwestern flank of the Vilyui paleorift. Data on the compositions of homogenous glasses of mineral-hosted melt inclusions yielded the P-T parameters of mantle sources of basic melts responsible for the formation of the Vilyui paleorift gabbro-dolerites. Two depth levels of basic melt generation have been established: 95-65 km at 1480-1400 °C and 55-45 km at 1360-1320 °C. Crystallization of the melts occurred at a shallow depth of 12-4 km with a decrease in temperature from 1185 to 1125 °С. This occurrence of basic melt sources at two different depths, as well as the heterogeneity of the chemical composition of melt inclusions and their host minerals explains the presence of two pulses of Devonian basic magmatism. Our new numerical thermomechanical model of magma rise during melting of the lithospheric mantle above a mantle plume supports the existence of two chambers at the spinel-garnet peridotite boundary and under the base of the crust, as well as the two-stage nature of Devonian magmatism.

We discuss the rocks of the Larba granulite block in the Ilikan zone of the Dzhugdzhur-Stanovoi superterrane. The Larba block is dominated by basic schists and garnet-biotite-orthopyroxene and garnet-biotite-cordierite-sillimanite gneisses (metabasites and metapelites). Calculation of temperatures and pressures of mineral formation was carried out by multi-equilibrium geothermobarometry, which makes it possible to evaluate the degree of equilibrium of mineral compositions along with P - T parameters. The P - T estimates have shown metamorphism of aluminous gneisses under moderate-pressure granulite facies conditions (7-8 kbar, 800-850 °C). Orthopyroxene granulites formed under granulite-amphibolite transition facies conditions. The mineral compositions and parageneses in highly ferrous metabasites permitted estimation of the conditions of metamorphism, P = 4-5 kbar and T = 630-700 °C, and show no influence of earlier granulite facies metamorphism. The bimodal P-T distribution for most samples of aluminous gneisses most probably reflects progressive and near-peak conditions of granulite metamorphism. The time of enderbite magmatism is determined from the upper intercept of discordia with concordia at 2546 ± 52 Ma and should be verified. The age of metamorphic rims over enderbite zircon is 1882 ± 11 Ma. The model Nd age of enderbites, t _Nd(DM) = 2.57-2.58 Ga, is close to the age of the core of enderbite zircon and differs significantly from the model Nd age of the host metamorphic rocks (2.8-3.0 Ga). The Paleoproterozoic metamorphism of the Larba block rocks regionally coincides with the third stage of collisional granitoid magmatism of the southeastern Siberian craton and records the formation of this structure.

Ecosystems of the fjell fields in the Khibiny Mountains (Kola Peninsula), were investigated, including vegetation, soils, soil algae and invertebrate fauna. We used EUNIS habitat typification (2013) to differentiation of habitats. The most common habitat types were: (1) Crustose-lichens (Rhizocarpon geographicum) rocks habitat type on eluvia of base-rich, alkaline and siliceous rocks (U5111); (2) The lichens-, sedges-and dwarf-shrubs-dominated turfs and cushions on gravelly and rocky slopes (U5112); (3) Sedge-, moss- and-lichens-dominated habitat type on rubble and stony mountain plateaus and peaks (U5113); (4) Biological soil crusts (BSCs) habitat type on fine-earth and gravelly polygons edges (U5114); (5) Late snow bed moss vegetation (U5115). Soils of the fjell fields were Leptosols. Content of soil organic C was very high (26-32 %) despite the thin soil profile, which had no illuvial-eluvial differentiation by the content of SiO2 и R2O3. The total flora includes 176 species of plants and lichens. Soil algae flora comprised 43 species, where green algae of Chlorophyceae prevailed. Among soil microarthropods prevailed Collembola, Oribatida and Mesostigmata, which were also typical for mountain tundra. The soil microbial activity, diversity and abundance of soil algae and invertebrates depend on habitat type, soil moisture, as well as soil organic matter contents and gets higher on wet substrata or in more complex vegetation.

The materials and performs a systematic analysis of the elemental composition of 110 species and 28 families of plants that form tree-shrub layers of forest phytocenoses and form the structure of urban landscaping in South Primorye in the article was summarizes. A high differentiation of the species composition in the accumulative abilities to the weight of the metal, especially Zn and Mn was noted. The most stable indicator among of the species was recorded on the Cu content. The types and families of high, low and background of heavy metals content are distinguished by the basis of the author’s indicator, i. e. “the relative intensity of accumulation (RIA)” of chemical elements. The low content of heavy metals is more typical for the main arboriflora composition. At the same time, about the half of the studied species is accumulated some metals above the background (average) exponents. The maximum of metals content (for the 5 times and high more than the background exponent) was recorded in the leaves (needles) of the concentrator species: Zn - Salix udensis, Populus maximowiczii, P. nigra, P. tremula, Syringa wolfii; Mn - Salix udensis, Sorbus pochuashanensis, Picea sp.; Fe - Crataegus pinnatifida. The high heavy metals content among the families is most typical for Hydrangeaceae and Salicaceae, the low content - for Fabaceae, Pinaceae, Tiliaceae and Aceraceae, the background level - for Rosaceae. The phytogeochemical systematics of the Far East arboriflora for species and family ranks on the basis research results was developed for the first time.

The work summarizes the results of long-term field studies of 22 species of halophytic plants in the Elton region, belonging to 4 families and 14 genera. Plants were classified according to the ecological (salt-accumulating euhalophytes, salt-secreting crinohalophytes, salt-excluding glycohalophytes) and genetic (C3-type and C4-type of photosynthesis) system. The conditions of the abiotic environment (level of salinity and soil moisture) under which various groups of halophytic plants grew are shown. The composition of fatty acids of lipids in halophyte leaves was analyzed. It is concluded that the modulation of halophyte lipids, associated with changes in fatty acids composition depending on soil salinity and moisture, is one of the mechanisms of plant salt tolerance at the cellular level of organization.

Urbanization ongoing around the world leads to changes in ecosystems, and wildlife is forced to respond by adapting to this impact. First of all, plant communities change, which are actively being transformed inside and around the city what, with the stress of human presence, does not remain indifferent and for animals. For animals this often leads to decrease in biodiversity in the sites exposed to anthropogenic stress. However, for some mammalian species (especially small ones) what are more resistant to stress from human presence, urbanization has some advantages by creating modified habitats and reducing competition with natural forest species that are more sensitive to urbanogenic effects. For several years, we have been investigating the influence of the megalopolis located in the forest zone (Ekaterinburg city) on phytocenoses and communities of small mammals. The objects were two park-forests - areas of pine forest of the city outskirts, altered to varying degrees depending on the proximity to urban development, as well as the remains of a pine forest in the Central Park of Culture and Recreation. The forest phytocenoses were found have been changed through all park-forests area, especially strongly in places adjacent or close to buildings at the cost of weed vegetation and introduced plant species, as well as under the influence of recreation. In addition to the forest species, small mammals uncharacteristic for the forest of this zone were present at all sites. In outlying park-forest places where the anthropogenic load is much lower, forest mammal species are found in greater numbers, although and the presence of hemisynanthropic species, which in our forests include small wood mouse and striped field mouse, remains. In some cases, this might lead to an increase in community diversity indices. Naturally, the conditions of the plant environment affect the ability of rodents and shrews to form steady micropopulations and communities in the forest sites of the city, although and the disquiet factor plays a material role.