Linear or lens-like carbonate (marble) and carbonate-silicate bodies among gabbro and amphibolites within the Krestovsky subterrane of the Olkhon composite terrane (West Baikal Area) are identified as dikes. The dikes commonly dip almost vertically, range in thickness from 20 cm to a few meters, and are up to 100 m long. The Olkhon marble dikes quite often coexist with dolerite dikes and/or granite veins and show signatures of emplacement synchronously with the igneous bodies. The marble dikes differ from mantle carbonatites in mineralogy and chemistry and thus may be derived from sedimentary carbonate rocks molten during collisional events.

The origin of the Olkhon carbonate and carbonate-silicate dikes may be explained with two possible geodynamic scenarios. They may be derived either from Neoproterozoic carbonate sediments upon the Early Precambrian basement of a cratonic block which was involved in collisional events, or from abundant carbonate sedimentary material in an island-arc terrane. Large-scale melting of silicate and carbonate rocks was maintained by heat released from mantle mafic magma intruding into the lower crust. The batches of both crustal (carbonate and granitic) and mantle (mafic) melts intruded late during the collision in a strike-slip tectonic setting.

There have been presented the results of the study of a thick (no less than 2–3 km), extended (for more than 200 km) volcanogenic formation (Tsetsen-Uul or Yargait) in the south of the Zavkhan terrane of the Central Asian fold belt. The formation is an assemblage of frequently intercalating effusive rocks of the subalkaline basalt-andesite-dacite-rhyolite series, their tuffs, tuffites, ignimbrites, and terrigenous rocks. Felsic rocks dominate over basites, and tuffogenic rocks dominate over effusives. There is some evidence that the formation emerged in a subaerial setting, with explosive eruptions, and the petrogeochemical features of the effusive rocks are typical for subduction environment. The felsic effusive rocks have high negative εNd from –11.5 to –12.8 and Early Precambrian model age TNd(DM)=2.4–2.5 Ga, which indicates the presence of an ancient crust at the depth and its involvement in magma. The evidence supports the formation of volcanic rocks within an active continental margin. The continental-margin formation stage ranges from ~860 Ma to ~780 Ma based on the LA-ICP-MS U-Pb dating of zircons.

The Tsetsen-Uul (Yargait) formation is similar in structure and composition to the Zavkhan formation of the Zavkhan terrane and the Sarkhoi group of the Tuva-Mongolian massif, and partially overlaps them in formation time. It is concluded that all three volcanogenic formations emerged in the same geodynamic setting and in the same time interval, and are the fragments of a continental volcanic arc belonging to both Zavkhan and Tuva-Mongolian paleomicrocontinents.

The results of U-Pb LA-ICP-MS dating of 150 detrital zircon grains from the Precambrian (Riphean?) sandstones of the Kildin group on the coast of the Ivanovka Bay (northeastern Kola Peninsula) are presented. A group of three youngest grains yielded constraint on the sandstone maximum depositional age of 1179±45 Ma. Detrital zircon age distribution is dominated by three maximums of 1.9, 2.4 and 2.7 Ga. The authors consider two complementary scenarios of interpretation of the data obtained. The first scenario involves the contribution of distant provenance out of granitoids in the Lapland-Kola orogen (~1.9 Ga) and adjacent areas of the Kola-Karelia region (~2.7 Ga), Imandra-Varzuga structure (~2.4 Ga), and Sveconorwegian belt (~1.2 Ga); the off-Baltic (Greenland?) sources of the detrital zircon also cannot be excluded. According to the second scenario, the Ivanovsky graben received zircons also from the proximal sources – sialic complexes formed upon melting of granite-gneiss substratum of the upper crust of the Murmansk craton during largescale episodic mafic magmatism 1.86, 2.50 and 2.68 Ga. The Raman spectroscopy showed that about 25 % of the analyzed detrital zircon grains experienced a 1.4-Ga-old thermal effect which did not lead to Pb losses but partially restored the crystalline structure of zircon. This result can be used as an additional constraint in the detailed provenance analysis of the northeastern East European Platform sedimentary basins and is indicative of 1.4-Ga-old large-scale magmatic events related to the breakup of the supercontinent Nuna.

This paper presents the results of petrographic, lithogeochemical, and U-Pb geochronological studies of detrital zircons in deep core sediments from the Vendian terrigenous sequences of the Nepa and Tira formations in the interior of the Siberian Platform. The section of the Nepa formation is characterized by a terrigenous sediment, the Tira Formation is composed mainly of carbonate rocks. The terrigenous rocks of the Nepa formation are composed of ill-sorted and poorly rounded clasts. Towards the higher part of the section of the Tira formation, there is observed an increase in the degree of sorting and roundness of detrital grains. It has been established that clastic rocks of the lower Nepа subformation are the products derived from rocks of mixed (acidic, basic) composition. The terrigenous rocks of the upper Nepa Subformation and the Tira formation accumulated mainly due to acid decomposition of rocks. The U-Pb (LA-ICP-MS) geochronological studies of detrital zircons from terrigenous rocks of the Nepa and Tira formations led to the conclusion that the sedimentary basin of these formations was contributred to by both the Archean-Early Proterozoic rocks in the basement of the Siberian Platform and the adjacent areas of the Central Asian foldbelt. It is assumed that the sediments of the lower Nepa subformation deposited in the residual basin, formed by joining of terrains and island arcs in the Paleoasian Ocean to the southern margin of the Siberian Platform during the Vendian accretionary-collisional events. This was followed by a transformation into a peripheral sedimentary basin and an occurrence of a transgression of the sea, which favored the accumulation of terrigenous-carbonate rocks of the Tira formation.

This paper presents the results of comprehensive geological and geochemical studies of sandstones from the Belaya basin of the Amur fragment of the Nora-Sukhotino terrane of the northeastern flank of South Mongolia-Khingan orogenic belt, as well as the results of isotopic (U-Th-Pb and Lu-Hf) studies of detrital zircons therefrom. The sandstones from the Belaya basin are characterized by significant variations in the composition of clastic material and major rock-forming elements, and by correspondence to arkoses and litharenites. They were accumulated due to erosion of geochemically mature felsic and intermediate igneous rocks. The sandstones are dominated by Ordovician, Cambrian, and Neoproterozoic zircons. The youngest zircons in sandstones from the Belaya basin are dated back to 451±8 Ma, with the lower age boundary set at the Late Ordovician. The Ordovician zircons, which have positive εHf(t) values and Early Paleozoic – Neoproterozoic Hf-model ages, could have been derived from island arc complexes. The Cambrian and Neoproterozoic zircon grains with positive εHf(t) values and Neo – Mesoproterozoic Hf-model ages could have been derived from Early Paleozoic and Neoproterozoic igneous rocks of the Bureya or Mamyn terranes. The available geological materials provide evidence that the sandstones from the Belaya basin are a fragment of the Early Paleozoic accretionary complex, which formed in the Early Paleozoic along the southeastern margin of the Mamyn (Xing’an) massif. However, a small amount of data on the Early Paleozoic and Neoproterozoic magmatism of the region hinders drawing more definite conclusions.

For the first time there were obtained LA-ICP-MS U-Pb age data on detrital zircons from sediments of the Bystraya and Ernichnaya formations of the Argun series of the northwestern Argun continental massif. The results obtained lead to the following conclusions: (1) the Bystraya series combines heterochronous Low Cambrian carbonate rocks and Upper Proterozoic terrigenous deposits; (2) the age of the youngest group of detrital zircons extracted from sediments of the Ernichnaya formation allows us to restrict the lower age limit to the Ediacaran (556±11 Ma), which does not contradict a standard stratigraphic age; (3) terrigenous materials entering the basin may come from the Argun continental massif. The inferred source areas of clastic materials are the Neo- and Paleoproterozoic magmatic and metamorphic formations, widespread across the Argun massif. Besides, the deposits we studied contain a smaller amount of the Mesoproterozoic zircons. Their provenance still remains unknown since the Argun massif does not include any Mesoproterozoic magmatic rocks with sufficiently accurate geochronological age estimates.

The paper provides an overview of the geological structure and presents new data on petrography and geochemistry of igneous rocks of the Tekturmas accretionary complex (TAC). Consideration is being given to the age, petrogenesis and probable tectonic settings of formation of igneous rocks. It is shown that the TAC and adjacent ophiolite belt are parts of the Late Cambrian – Ordovician Pacific-type orogenic belt formed at an active margin of the Paleo-Asian Ocean. The TAC is dominated mainly by tholeiitic mafic igneous rocks (basalt, dolerite, gabbro). There are recognized three groups of rocks: high-Ti, medium-Ti and low-Ti. Geological and geochemical features of TAC igneous rocks suggest their formation in three tectonic settings: mid-ocean ridge (medium-Ti), oceanic island/seamount (high-Ti) and over subduction zones (low-Ti).

The paper presents the first results of U-Th-Pb (LA-ICP-MS) isotopic dating of detrital zircons from the Paleozoic (?) metasedimentary rocks of the Nilan Terrane of the Mongol-Okhotsk orogenic belt to refine the age estimates and determine their probable correlation with earlier dated sediments of this belt. It has been stated that the metasedimentary rocks of the Olga, Salarin and Rovnen formations and of the Sivak formation of the Nilan terrane are characterized by the almost complete absence of the Early Precambrian zircons, slightly negative εNd(t) values, and Mesoproterozoic tNd(DM) and tNd(С) values. The isotope dataset obtained shows that most of the detrital sediments were carried from continental massifs of the Amur superterrane.

East Asia is the vast region of Asia which is characterized by a complex geological structure and high activity of seismic and tectonic processes. Satellite geodetic data, reflecting the recent crustal movements in the region, demonstrate a considerable variability in magnitude and direction of motions both along the strike of island-arc margins and deep into the continent. To explain the anomalies in the Earth's surface displacement field, the paper proposes a geodynamic model of East Asia which involves the mechanism of interaction between the continental lithosphere of the region and the continent-to-ocean transition area along the Kuril-Kamchatka and Japanese island arcs. The proposed concept includes the model of the upper-mantle convective cell, developing beneath the continental lithosphere, in combination with the keyboard-block model explaining the regularities of seismic cycle in the island-arc margins. It has been shown that the consideration of interaction between the lithosphere and upper mantle in the continent-to-ocean transition area in the framework of the model of non-stationary convective cell allows us to explain the recent crustal movements observed up to a distance of 2000 km and the seismic tomography data without involving additional lithospheric blocks. The model contributes to the development of the physically grounded geodynamic approach to the analysis of recent tectonics and eliminates the inconsistencies between the observed data and classical plate tectonics in East Asia.

This paper presents the results of a study on traces of ancient earthquakes in the lake bottom sediments of eastern Fennoscandia (Kola region and Karelia). Based on the sediment cores from six lake basins located within large active structures of the region, consideration is being given to the most typical features of sedimentation affected by neotectonic movements of the Earth’s crust. The data presented here provide lithological-stratigraphical, paleobotanical and chronometrical evidence for lakes. The paper causes and mechanisms of formation of seismic structures in bottom sediments and their distinction from deformations of another origin.

Generalized earthquake history in provided an opportunity to organize the existing information on the time of paleoearthquake manifestations and distinguish three active periods in paleoseismicity. These are Late Glaciation-Early Holocene marked by the most rapid uplift after the retreat of the last ice sheet (13500–8100 cal yr BP), Middle Holocene (6800–6600 cal yr BP), and Late Holocene (3100–200 cal yr BP). The results of this study showed that the number and intensity of seismic events changed at different stages of sedimentation. Since the Younger Dryas, fault zones (or their segments) have been repeatedly activated. Combined with the data on paleoseismicity in adjacent parts of Fennoscandia, our studies indicate an irregular pattern of the Late Pleistocene-Holocene seismic activity in stable areas formerly covered by glaciers. The obtained data make further adjustments to the neogeodynamic and seismic estimates of intraplate areas.

The article deals with the first results of integrated geohazard monitoring conducted by the Institute of the Earth’s Crust SB RAS on the territory of Pribaikalye in 2020. The pilot network consists of three sites: "Buguldeika", "Priolkhonye" and "Listvyanka", each of which is equipped with high-precision digital devices including a broadband seismic station, a GPS receiver, deformometers, a sensor of soil radon emanations, and an observation station for the Earth’s electromagnetic environment. This equipment is designed to acquire quantitative information on rock deformation, recent movements and geophysical field variations for solving theoretical and applied problems of geodynamics and seismology, including development of earthquake prediction methods. In the vicinity of the sites, there have been made the hydroisotopic measurements as well as observations over the character of some of exogenous processes. Based on the comprehensive analysis of the seismological, tectonic, deformation and emanation data, acquired also through monitoring, there has been obtained the preliminary characteristics of the Kudarinsky earthquake (December 9, 2020, MW=5.6) that was followed by intensity 5 aftershocks in large cities of the southeastern East Siberia – Irkutsk, Shelekhov, Angarsk, Usolye-Sibirskoe and others. It has been found that the seismic event manifested itself almost in all the fields monitored. This implies the network efficiency for a purposeful study of the precursors of large earthquakes which can initiate the development of other hazardous geological processes in Pribaikalye. The deformation monitoring data show some general patterns of earthquake source evolution which corresponds to the fundamental principles of physical mesomechanics. This opens the prospects for diagnostics of the final phase of earthquake generation in the context of meta-instable state of deformation process and rock mass disintegration.

Petrophysical, tectonophysical and paleomagnetic studies were done on the field of diamonds from the Komsomolskaya kimberlite pipe to interpret the observed gravimagnetic field. As a result of studying the structural-material complexes (SMC) of the field, there was formed a dynamic physical-geological model (DPhGM). The structure of the deposit is a dynamically developing network of faults that control heterochronous igneous complexes (kimberlites and traps). The features of the tectonic structure and physical properties of the SMC of the field were reflected in the nature of the observed gravitational and magnetic fields. DPhGM provides proofs for the existence of geophysical anomalies, genetically related to the structures of diatreme association – anomalies of the structural type.

The Main Saranovskoe deposit is one of the largest chrome deposits in Russia. The chrome ore bodies are localized in the ultramafites of the Northern Saranovsky massif which has been studied since 1907. The research revealed that the massif is similar to the Bushveld stratiform complex. Unlike other layered plutons, the Northern Saranovsky massif has a large amount of chrome ore bodies as compared to ultramafic host rocks. As many studies have shown, the chromitites of the Main Saranovskoe deposit are severely tectonized. The strike and dip of the ore bodies is complicated by numerous faults. These observations imply that the massif is a fragment of a large stratified pluton intruded into the Proterozoic metasedimentary unit. The fracturing reflects the massif intrusion conditions and provides new petrogenetic information on the relevance of our study of the tectonic fractures of the Saranovsky massif. Studies have been made on the fracture and furrow displacement orientations along the planes in the main ore bodies: western, central and eastern, within the two parts of the deposit. The local stress tensor has been reconstructed using the Angelier method in the Win-Tensor program. It has been stated that the chromitites studied contain 3–4 main fracture systems whose orientation varies together with the orientation of the ore bodies. The main compressive stress axis is oriented subvertically both in the central and southern parts of the deposit, and the main tensile stress axis forms an acute angle with the ore body contacts in the center of the deposit and is oriented subperpendicular to them in the southern part. It has been concluded that fracturing of the chrome ore bodies in the Main Saranskoe deposit took place during the massif motion into the upper crustal horizons with the subvertical orientation of the ore bodies remained unchanged. This casts doubts on the probability of formation of the Northern Saransky massif as a result of gravity differentiation of magmatic melt, since in this case the ore bodies should have undergone a vertical turn which is not exhibited by their fracturing.

The paper considers the properties of statistical function whose plot comprises a set of measurements of H-component of the magnetic field. There has been found a set of quasi-linear objects with very similar parameters. In the context of a hypothesis about the correspondence of these structures to seismic processes, there has been made an estimate of time intervals typical for the phases of decrease and increase in the level of compression of lithospheric plate material in the earthquake source zones. It has been shown that the application of statistical methods in geophysics may contribute to near real-time assessment of seismic hazard in the study area.