The number Ka=N/N₁ is used to evaluate the thermal power of a plume; N is the thermal power transferred from the plume base to its conduit, and N₁ is the thermal power transferred from the plume conduit into the surrounding mantle. At the relative thermal power 1.9<Ka<10, after eruption of the melt from the plume conduit to the surface, melting occurs in the crustal block above the plume roof, resulting in the formation of a mushroom-shaped head of the plume. A thermochemical plume originates at the core-mantle boundary and ascends (melts up) to the surface. Based on laboratory and theoretical modeling data, we present the flow structure of melt in the conduit and the head of the thermochemical plume. The features of melting in the plume conduit are elucidated on the basis of the phase diagram of the CaO-MgO-Al₂O₃-SiO₂ model system. The two upper convection cells of the plume conduit relate to the region of basic and ultrabasic compositions. Our study shows that melting in these cells proceeds according to monovariant equilibria of eutectic type L=Cpx+Opx+An+Sp and L=Fo+An+Cpx+Opx. In case of the CaO–MgO–Al₂O₃–SiO₂–Na₂O system, crystallization differentiation proceeds as separation of plagioclase crystals. Separation of plagioclase crystals enriched in anorthite component leads to enrichment of the residual melt in silica and alkaline components. Assuming the initial basaltic melt, we calculated the compositional changes in the melt, which are powered by the heat and mass transfer processes in the mushroom-shaped plume head. The calculations were performed in two stages: (1) after settling of refractory minerals; (2) after settling of plagioclase in the melt resulting from the first stage. In the second stage, the melt contains 88.5 % of plagioclase component. The calculations were performed for melt temperature T_melt=1410 °C and pressure P=2.6 kbar and 6.3 kbar. The calculated weight contents of oxides, the normative compositions for solid phase, and the oxide content and normative composition for the residual melt were tabulated. The SiO₂ content in the residual melt amounts to 59.6–62.3 % and corresponds to the crustal SiO₂ content.

The sources of the natural stress-strain state (SSS) of epiplatform orogens are investigated by tectonophysical methods based on seismological data. According to the available data, the horizontal axes of the main deviatoric extension are dominant in depressions, while in the ridges of the orogens, the axes of the main deviatorial compression are dominant.Our comparative analysis is focused on SSS of the orogenic crust. It is generally accepted that the sources of such SSS are geodynamic processes, including the pressure on the Eurasian Plate from the Indian Plate, and the small-scale thermogravitational asthenospheric convection. In the mathematical (analytical) simulation technique used in our study, the main criterion for the correctness of models in terms of tectonophysics is the correspondence between the orientation pattern of the principal stress tensor axes in the crust model to the natural data. According to Model I, the lithospheric SSS under lateral compression is less consistent with the sought-for SSS. Model II also gives the results that do not fully correspond to the stress data from tectonophysical reconstructions. However, additional analysis suggests that asthenospheric convection is a more promising (from the point of view of tectonophysics) geodynamic process for explaining epiplatform orogenesis. In our opinion, more complex and probably non-analytical mathematical models should consider this source of loading of the lithosphere as one of the most significant factors in the formation of the orogenic crust SSS in Central Asia.

Tectonophysical experiments show that the evolution of the Fen-Wei Rift is controlled by oblique rifting. A key characteristic of the model in our study is that the western and eastern borders of the transfer zone between the adjacent NEE-striking extensional basins tend to form right-lateral strike-slip faults with slight normal slip as a result of the interaction between the adjacent NEE-striking extensional basins under oblique rifting. The current deformation of the Fen-Wei Rift can be clarified by testing this predicted deformation characteristic. Our analysis of the relocation and focal mechanism solutions of the 1989 M 6.1 Datong-Yanggao earthquake swarm, which was the largest earthquake that occurred in the Fen-Wei Rift in the last 200 years, suggests that the transfer zone between the Yangyuan and Hunyuan basins is bounded by the NNE-striking right-lateral strike-slip faults with slight normal slip at its eastern and western edges. This consistency between the model and the current tectonic activity in the study area indicates that oblique rifting still plays an important role in the current deformation of the northern Fen-Wei Rift.

The article presents the main results of more than forty-year studies of the hydrogeodeformation field. We have establish some new properties of lithospheric massifs, which are clearly detectable during the periods of fast geodynamic activation (FGeDA). These processes are contrastingly manifested within the planetary megastructure – the Global Endodrainage System (GEDS) of the Earth. The article discusses ideas about the conditions of formation, the specific features of functioning and the role of the asthenosphere as an essential element of the GEDS. It shows the dominant role of fluid processes that take place in the GEDS and provide the conditions for the ‘maturation’ of geodynamic catastrophes. The features of the formation of deformation disturbances and the dominant directions of the planetary migration of deformation impulses from the places of future catastrophic seismic events along the GEDS are considered. The regional hydrogeodeformation monitoring (HDGM) results give evidence of a close relationship between the lithospheric massifs in distant regions of the Earth: replica signals along the GDES length repeat an initial impulse originating from the area of a future seismic event. Attention is given to trigger effects that cause a seismic energy discharge at a large distance and, in some cases, can cause a cascade of earthquakes. It is proposed to create a HDGM system for monitoring of large seismic regions of the Earth.

The history of the Central Asian Orogenic Belt (CAOB) was marked by several major events of magmatism which produced large volumes of volcanic and intrusive (mafic-ultramafic and granitic) rocks within a relatively short time span (30–40 Ma) over a vast area. The magmatic activity postdated the orogenic stages of accretionary-collisional belts in Central Asia and likely resulted from the impact of mantle plumes that formed Large Igneous Provinces (LIPs). The formation of the Tarim–South Mongolia LIP at 300–270 Ma is the best known among the major Permian events of basaltic and granitic magmatism. Early Permian igneous rocks (volcanic, subvolcanic and intrusive suites that vary from ultramafic to felsic compositions) of the same age range (300 to 270 Ma) have been recently found also in Eastern Kazakhstan, within the late Paleozoic Altai collisional system. The compositions and ages of the rocks suggest that the Eastern Kazakhstan magmatism was the northward expansion of the Tarim LIP. The spread of the Tarim LIP was apparently facilitated by lithospheric extension after the Siberia-Kazakhstan collision. The extension led to rheological weakening of the lithosphere whereby deep mantle melts could penetrate to shallower depths. The early Permian history of Eastern Kazakhstan was controlled by the interplay of plate tectonic and plume processes: plate-tectonic accretion and collision formed the structural framework, and the Tarim mantle plume was a heat source maintaining voluminous magma generation.

The Markov Deep (the axial part of the slow-spreading Mid-Atlantic Ridge, 6°N, Sierra Leone oceanic core complex) and the Paleozoic Voikar ophiolite association (Polar Urals) formed in the back-arc sea conditions. In both cases, the lower crust of a close structure was formed on the basements composed ofdepleted peridotites of the ancient lithospheric mantle. The available data show that the composition of the lower crust of the oceans and back-arc seas is dominated by layeredmafic-ultramafic intrusions originating from the MORB melts, and suggest a similar asthenospheric source of magmas. Sills and dykes formed from other magma sources represent the second structural element of the lower oceanic crust: in case of the ocean, mainly ferrogabbroids originating from specific melts with the OIB involvement, and, in case of the back-sea sea, gabbro-norites of the supra-subduction calc-alkaline series. In both cases, the upper crust originates frombasaltic flows that occurred later and are associated with new episodes in the tectonic development. According to [Sharkov, 2012], the development of slow-spreading ridges takes place in discrete impulses and non-simultaneously along their entire length. Furthermore, oceanic core complexes (OCC) in their axial parts are the ridge segments, where spreading is resumed. At the OCC stage, newly formed basalt melts move upwards from the magma generation zone into fractures (dykes) through the lithospheric mantle, and the thickness of the lower crust is built up by sills. As spreading develops in this area, the crust becomes thicker from below due to underplating in form of large layered intrusions. The newly formed restites, in their turn, cause an increase in the lithospheric mantle thickness from below. Apparently, the lower crust formed in the back-arc seas according to a similar scenario, although complicated by the processes taking place in the subduction zone.

In 2000–2017, the GPS technology was first applied to study inter-seismic, co-seismic and post-seismic processes in the crust of the Altai Mountains (Gorny Altai). Our study aims at investigating the fields of displacement and deformation in the Gorny Altai region as a part of Asia.The 3D displacement fields are reconstructed for the period before the M 7.3 Chuya earthquake that occurred in the southern sector of the Altai GPS network (49° to 55°N, and 81° to 89°E)on 27 September 2003.Anomalous behavior features are discovered in the displacement orientations, as well as in the distribution of velocities and deformation in the zone of the future earthquake.The spatial displacement pattern defined for the period of co-seismic displacements corresponds to the right-lateral strike-slip along the vertical fault. The fault depth is estimated using the elastic model and the experimental data (change in displacement from 0.30 m to 0.02 m at the distances of 14 km and 84 km from the fault, respectively); it amounts to 8–10 km.The co-seismic deformation field is investigated.In the post-seismic stage (2004–2017), displacements revealedin the epicentral zone show the right-lateral strike-slip along the fault at the rate of 2 mm/yr. Therefore, two-layer viscoelastic models can be considered. The estimated viscosity of the lower crust ranges from 6×10¹⁹ to 3×10²⁰Pa×s, and the elastic upper crust thickness is 25 km. Analyzed are modern movements in the Gorny Altai region outside the Chuya earthquake area.The results of our study show that modern horizontal displacements occur in the NNW direction at the rate of 1.1 mm/yr, which is twice lower than the displacement rate before the earthquake.

Our detailed study of the crust and upper mantle of the South Baikal basin focused on seismic coda and seismic S-waves attenuation and estimated seismic quality factor (Q_S and Q_C), frequency parameter (n), attenuation coefficient (δ), total attenuation (Q_T), and the ratio of two components the total attenuation: intrinsic attenuation (Q_i), and attenuation due to scattering caused by the inhomogeneities of the medium (Q_SC). We calculated the sizes of inhomogeneities revealed in the block medium, which put their effect on the attenuation of seismic waves in different frequency ranges. The seismic wave attenuation field was analyzed in comparison with the geological and geophysical characteristics of the medium, and a direct relationship was established between attenuation, composition and active processes in the crust and upper mantle of the studied area. According to the estimated intrinsic attenuation (Q_i) and scattering attenuation (Q_SC) contributions into the total attenuation, intrinsic attenuation is generally dominant in the studied area, while the Q_SC component increases in the areas of large active faults.

The Kurai Basin of Gorny Altai is located in the area of high seismic activity, which is involved in the focal zone of the 2003 M7.3 Chuya earthquake. Its aftershock process has not ceased yet, and shows the likelihood of major seismic events. The seismic monitoring records of the last 15 years after the devastating earthquake show the state of stress in the basin. A comprehensive field database has been consolidated from the studies of direct and alternating currents by electromagnetic methods, including transient electromagnetic sounding, vertical electrical sounding, and electric field tomography. Using a combination of the research techniques and the method of interpretation based on data inversion, it becomes possible to select optimal models, ensure higher reliability, and improve the contents of the study. The available seismological data are used to identify the zones of concentration of seismic events in the southern mountain frame of the Kurai Basin. Our study aims to determine and clarify the geoelectric structure of the southern troughs. The first section of the Southwestern trough is constructed, and the latitudinal fault boundaries of the Eshtykel graben are confirmed. A comparison of electromagnetic and seismic data for 2015 shows that the earthquake epicenters were mainly confined to the submeridional fault zones. In our study of the Southwestern trough, it is established that most of the earthquakes concentrated in active fault structures separating the blocks of varying depths, which are identified from the geoelectric data. The southern piedmont troughs of the Kurai Basin are cut by numerous faults of latitudinal and submeridional strikes.

Nikolai Aleksandrovich Florensov is a Russian scientist who is famous for his contribution to the theoretical foundations of structural geomorphology.He formulated the law of the circulation of material in the Earth's crust, which is manifested by a periodically arisinglithodynamicflow, in the development cycle of which two main phases are distinguished as ascending and descending geodynamics. In our opinion, there is also the third phase, stabilization.This process is reflected in the morphological types of mountains. Considering the conditions of intracontinental orogeny, N.A.Florensovdistinguished two main types: constructive and destructive.Developing this concept, he solved a number of theoretical and philosophical problems concerning the inextricable relationship between the relief and the structure of the geological substratum, its geodynamics and, as a consequence, proposed to consider their relationship as changes in geomorphological formations in time and space. The scientific creativity of NA. Florensov, as a whole, is comparable in importance with that of other most prominent geomorphologists of the late 19th and 20th centuries, including V.M. Davis, W. Penk, S.S. Shults, I.P. Gerasimov, and L. King.