Том 513, № 1 (2023)

The paper deals with the results of geological and geophysical research of shallow-water areas of the East Siberian Sea, started in 2018 in the frame of State Geological Mapping project (Geological Map of 1 : 1 000 000 scale) and continued in 2022 under support of the Russian Science Foundation project. The seismostratigraphic scheme of the Quaternary sediment sequence is compiled, and the conception of the palaeogeographical evolution in the Late Pleistocene-Holocene is proposed.

The age of magmatic rocks of the basic composition sampled at the Alpha-Mendeleev Rise in the Arctic Ocean with the help of a research submarine was studied, based on the measurement of the U/Pb age of zircons separated from them. Early Cretaceous rocks of the moderately alkaline series, formed at the turn of 112 million years, are most common on the Rise. These rocks contain a large number of ancient xenogenic zircons, the age analysis of which shows that the subalkaline melts interacted with the crust at two levels: with the horizon of Early Cretaceous sandstones and with rocks of the Late Archean crystalline basement with an age of 2675.1 ± 11.6 million years. They also contain a small number of younger zircons with an age of 83–87 million years, which probably arose during the recrystallization of Early Cretaceous zircons under the influence of Late Cretaceous magmatism.

In the present contribution, we aim to determine the age of the oldest arc-related volcanic units in the North Tianshan of Kyrgyzstan (NTS) to better understand the early evolution of subduction systems in the western part of the Central Asian Orogenic Belt. We conducted zircon U–Pb dating (LA–ICP–MS) on andesitic tuffs from the Sultansary and Tashtambektor formations, which were previously believed to be of early Cambrian and middle Cambrian to early Ordovician age, respectively. Our results reveal age estimates of 491 ± 3 and 487 ± 3 Ma for these formations, indicating that both units are late Cambrian in age. The volcanic rocks belong to a major magmatic arc with a heterogeneous basement that evolved in the NTS during the late Cambrian and early Ordovician.

During the second half of the 20th century by the end of the first quarter of the 21st century the problem of differentiation and correlation of the main rivers of Western Siberia (primarily the Ob and Yenisey) valleys sediments was intensively discussed. Traditionally, the regional Quaternary history of the river valleys was considered as the “terrace flight” paradigm. According to it in the Neogene-Quaternary time alluvial terraces formed by sequentially from the older upper to the younger lower ones. It was considered that terrace formed by neotectonics, paleoclimate dynamics changed the fullness of the rivers, advance of the sea and dereliction influenced on base of erosion and blocking river valley by northern glaciers. As a result, in outside glacier zone appeared barrier basins and periglacial alluvium. However, on the official maps of the Quaternary deposits the heights, age and even the number of terraces differ significantly. Nowadays a lot of data are contrary to theory about flight consistently carved cycloclimatic terraces and periglacial alluvium facies replacing the ice-dammed northern lakes in the south of Western Siberia. In the article it was performed the updated concept of the sedimental structure of the Upper Neopleistocene in the main valleys of the region and taking into account data on glacier outburst floods from intermountain area to the plain. Its intensive erosional and accumulative activity has so far been underestimated.

The material composition, structural and textural features of porphyry-copper-gold ore reflect the conditions of ore formation and are of decisive importance for predicting the technological properties of ore and increasing the complexity of the use of mineral raw materials. The sequence of ore formation with three stages identified: greisen, sulfide (productive) and explosive microzones within the studied interval of the ore body is presented. Features of ore and rock-forming minerals that determine their flotation behavior and properties that hinder the selectivity of flotation were revealed. The complex composition of the studied ore was established.

At the boundary of the Meso- and Neoproterozoic, Grenville collision events were widely manifested on the margins of ancient continental blocks. Most of the sedimentary sequences that had accumulated by that time had undergone significant thermal–metamorphic changes. In many ways, this is the main reason for the lack of isotopic data for carbonate deposits in the interval of 1200–900 Ma in world practice. Sr–isotopic composition in carbonate rocks with an age of 980–920 Ma was determined in the only section of the World – the Huainan Formation of the North China Platform with accumulation time determined by U–Pb dating of detrital zircon grains. In the upper part of the Nizhny Tunguska suite of the Turukhansk uplift, among carbonate deposits, we established the presence of altered volcanic rocks, as well as weathering crust products along them – poor bauxite and chamosite ores. Based on U–Pb zircon isotope dating, the age of the volcanic rocks is 964 Ma. For the least altered limestones of the upper part of the Nizhny Tungusska Formation, received ⁸⁷Sr/⁸⁶Sr values are 0.70532–0.70578, which are close enough to those found in the rocks of the Huainan Formation. Geochronological age of the studied limestones gives us more correct data. These data can be used to refine the previously proposed configuration of the Sr–isotopic composition variation curve in the Early Neoproterozoic. The Nizhny Tunguska Formation is the only carbonate section of the Early Neoproterozoic in the world with correctly geochronologically substantiated dating (based on zircon from subsynchronous volcanic rocks). This compares favorably with the Huainan formation.

The unusual composition of the protolith, its structural and textural heterogeneity, limited mass transfer and high temperatures are the causes of rare mineral formation and mineral associations during metamorphism and metasomatism. Most often, this is observed in shallow conditions (pressure up to 3 kbar) when additional heat is supplied to the rocks by magmatic intrusions. In the article, these issues are discussed on a number of geological complexes, in which the manifestations of metamorphism with the development of rare minerals and mineral associations have been studied in detail.

The Tatar bauxite deposit on the territory of the Russian Federation was formed as a result of sedimentation in contact-karst depressions of the products of denudation of lateritic weathering crusts of amphibolites. Detailed mineralogical studies of bauxites made it possible to reliably reconstruct the conditions for their formation. As it turned out parent rocks and weathered before rocks occurred due to the close location of the areas of nutrition and accumulation and denudation. At the same time, chemical processes was continuing in karst depressions. For the first time, the presence of nanoparticles of amorphous aluminum oxide was revealed into contact-karst bauxites. This characteristic feature of the form of alumina precipitation is associated with the subsequent cessation of lateritization processes and their attenuation with depth. The presence of amorphous aluminum monohydrate must be taken into account when choosing a scheme for bauxite enrichment.

The paper presents new deep velocity of the earth’s crust and upper mantle in the Khibiny-Lovozero tectonic region located on the Kola Peninsula. The artifacts of plume-lithospheric interactions that occurred in the investigated area from the Proterozoic to the Paleozoic time are discussed. A detailed comparison of the velocity structure of the Imandra-Varzug rift, the Khibiny and Lovozero plutons, and the adjacent Archean part of the Fennoscandinavian Shield has been carried out. A significant heterogeneity of the structure of the crust, upper mantle, as well as the structure and depth of the crust-mantle transition is shown. The presence of a zone of low seismic velocities in the upper mantle associated with the mid-lithospheric discontinuity (MLD) has been revealed. Structural features of the Moho zone and the upper mantle in the region of the Khibiny and Lovozero plutons were interpreted as artifacts of the plume process.

In a detailed analysis of the local features of the stress-strain state within the framework of the geomechanical model of Southern California, a rapidly developing high-amplitude shear deformation anomaly was identified in the upper crustal interval (at depths of up to 10 km) – the so-called “intense deformation quantum” – with a maximum increase in deformation by two orders of magnitude within 0.5 month. Such “quanta” can be integral elements of the entire deep deformation process associated with seismicity. The paper discusses the quantitative characteristics of deep deformation “quanta” and the conditions for their occurrence.

For the first time, a continuous two-year study of the particle fluxes and associated environmental parameters in the axial zone of the Arctic segment of the Mid-Atlantic Ridge at the junction of the Mohns and Knipovich Ridges (Norwegian Sea) was carried out. Sediment traps were deployed from the R/V Akademik Mstislav Keldysh in June 2019 in the northeastern part of the Mohns Ridge and realized in July 2020. It was shown that the sedimentation of sinking particles in the study area was influenced by the global transport of water masses in the northeastern direction, with Atlantic waters in the subsurface, and water masses of Arctic origin recirculating deeper in the subsurface. A weak positive temperature trend at a depth of more than 2500 m (0.02°C) is detected. The bimodal vertical distribution of fluxes and changes in the composition of sinking particles corresponded to the pattern of sediment recycling in the ocean. The annual course of fluxes in the subsurface layer was determined by the activity of silicon-concentrating and calcifying plankton, with the maximum bloom period also manifested in the deep layer. At the same time, the main significant moderator of flux deeper than 2000 m is the inflow of lithogenic matter from the benthic nepheloid layer.

According to the data on the sizes and intensity of tornadoes and landspouts, their characteristic times and forcings are found. Depending on the intensity, the average times vary by a factor of 3 and the forcings by a factor of 6. The energy of the vortices has been estimated and is expressed, among other things, in TNT equivalent mass units.

During laboratorial study we have get data about mineral and granulometric composition, some physical and physico-chemical parameters of mudflow deposit, which made it possible to identify soil features in mudflows in Chukotka. Made a try to estimate influence this influence of these features on the formation of mudflow suspension, which is the transport substance of mudflow. In terms of structural rheological movement model, mostly cohesionless mudflow suppose to be formed within reviewed territory, in which main mass of water is in free state. However, laboratory investigations have shown high contain of fine-grained particles in samples of mudflow deposit, which is in aggregated state. When flooded, these particles saturate water flow with clay suspension that allows classification this flows as cohesive. The cohesion of mudflow mass is acquired by flows in the process of movement at the expense of aggregates destruction that leads to changing physical characteristics of the mudflow.

The interaction of alpha radiation from UO₂ micro- and nanoparticles (uraninite) with the substance was visualized using alpha-autoradiography data on A-2 thick-layer nuclear photographic emulsions. The spherical area of action of alpha particles around UO₂ micrograins, up to 100 microns in size, is a deeply transformed substance with a high density of radiation defects. The translation of these results on a living organism leads to the conclusion about the specific type of impact of micro- and nanoparticles of depleted uranium, in which prolonged internal irradiation in small doses of the whole organism is combined with catastrophically high doses of alpha radiation in local zones, near micro- and nanoparticles UO₂.