A key role in developing the Earth theory is played by comparative studies of orogens, rifts, and platforms in the equatorial, middle and high latitudes of Asia and the adjacent Arctic regions. The modern shape of the planet’s triaxial asymmetrical cardioid ellipsoid results from its latest (Late Phanerozoic) geodynamic evolution that began in Arctic and then commenced in Asia. At this stage, mechanisms of the lithosphere extension and compression, combined with extension, were launched in Arctic and Asia, respectively. The special issue of Geodynamics & Tectonophysics presents papers on this topic.

In our study, we have developed a new tectonic scheme of the Arctic Ocean, which is based mainly on seismic profiles obtained in the Arctic-2011, Arctic-2012 and Arctic-2014 Projects implemented in Russia. Having interpreted many seismic profiles, we propose a new seismic stratigraphy of the Arctic Ocean. Our main conclusions are drawn from the interpretation of the seismic profiles and the analysis of the regional geological data. The results of our study show that rift systems within the Laptev, the East Siberian and the Chukchi Seas were formed not earlier than Aptian. The geological structure of the Eurasian, Podvodnikov, Toll and Makarov Basins is described in this paper. Having synthesized all the available data on the study area, we propose the following model of the geological history of the Arctic Ocean: 1. The Canada Basin formed till the Aptian (probably, during Hauterivian-Barremian time). 2. During the Aptian-Albian, large-scale tectonic and magmatic events took place, including plume magmatism in the area of the De Long Islands, Mendeleev Ridge and other regions. Continental rifting started after the completion of the Verkhoyansk-Chukotka orogenу, and rifting occurred on the shelf of the Laptev, East Siberian, North Chukchi and South Chukchi basins, and the Chukchi Plateau; simultaneously, continental rifting started in the Podvodnikov and Toll basins. 3. Perhaps the Late Cretaceous rifting continued in the Podvodnikov and Toll basins. 4. At the end of the Late Cretaceous and Paleocene, the Makarov basin was formed by rifting, although local spreading of oceanic crust during its formation cannot be excluded. 5. The Eurasian Basin started to open in the Early Eocene. We, of course, accept that our model of the geological history of the Arctic Ocean, being preliminary and debatable, may need further refining. In this paper, we have shown a link between the continental rift systems on the shelf and the formation history of the Arctic Ocean.

A comprehensive model for deep dynamics in Asia has been developed from the data on the evolution of melting anomalies in the context of lithospheric plate motions, interactions, orogeny, and rifting. The key components of our model are the primary (transition layer) and secondary (upper mantle) melting anomalies (Gobi, Baikal, and North Transbaikalia; and Hangay, Sayan, and Vitim, respectively). It is inferred that the primary melting anomalies originated at the beginning of the latest geodynamic stage (ca. 90 Ma) as a result of the transition layer distortion by lower mantle flows. Such primary anomalies were caused by avalanche collapses of the slab material that had been stagnated under the closed fragments of the Solonker, Ural-Mongolian paleooceans and the Mongol-Okhotsk Bay of Paleopacific. The secondary melting anomalies occurred due to the Early-Middle Miocene structural reorganization in the Pacific-Asian and Indo-Asian interaction zones. The primary melting anomalies governed the spatial distribution of forces and processes of the latest geodynamic stage. The secondary melting anomalies resulted from the lithospheric motions relative to the primary anomalies and provided for the development of orogeny and rifting. The Baikal-Mongolian corridor of asthenospheric flows was limited by the lateral zones of convergent interactions between India and Asia in the southwest, and North America and Asia in the northeast. In these lateral zones, Late Phanerozoic paleoslabs and ascending mantle fluxes were revealed in the transition layer, as well as in the upper mantle, without any destruction by the asthenospheric flows.

We have studied the structural geology and geomorphology of the fault zones in the junction area of the Angara-Lena uplift and the Predbaikalsky trough. We have analyzed faults and folds and reconstructed paleostresses for this junction area named the Irkutsk amphitheatre. Our study shows that syn-fold (Middle Paleozoic) faults include thrusts, reverse faults and strike-slip faults with reverse components, that occurred due to compression from the neighbouring folded region. Recently, contrary to compression, faulting took place under the conditions of extension of the sedimentary cover: most of these recent faults have been classified as normal faults. In the Late Cenozoic, the platform cover was subjected to brittle and partly plicative deformation due to the NW–SE-trending extension that is most clearly observed in the adjacent Baikal rift. Thus, the divergent boundary between the Siberian block of the North Eurasian plate and the Transbaikalia block of the Amur plate is a zone of dynamic influence, which occupies the area considerably exceeding the mountainous region on the Siberian platform. Important factors of faulting are differentiated vertical movements of the blocks comprising the platform. Such vertical movements might have been related to displacements of brine volumes. In the Late Cenozoic basins, movements along separate faults took place in the Late Pleistocene – Holocene.

Attenuation of seismic waves in the crust and the upper mantle has been studied in three global rift systems: the Baikal rift system (Eurasia), the North Tanzanian divergence zone (Africa) and the Basin and Range Province (North America). Using the records of direct and coda waves of regional earthquakes, the single scattering
theory [Aki, Chouet, 1975], the hybrid model from [Zeng, 1991] and the approach described in [Wennerberg, 1993], we estimated the seismic quality factor (Q_C), frequency parameter (n), attenuation coefficient (δ), and total attenuation (Q_T). In addition, we evaluated the contributions of two components into total attenuation: intrinsic attenuation (Q_i), and scattering attenuation (Q_sc). Values of Q_C are strongly dependent on the frequency within the range of 0.2–16 Hz, as well as on the length of the coda processing window. The observed increase of Q_C with larger lengths of the coda processing window can be interpreted as a decrease in attenuation with increasing depth. Having compared the depth variations in the attenuation coefficient (δ) and the frequency (n) with the velocity structures of the studied regions, we conclude that seismic wave attenuation changes at the velocity boundaries in the medium. Moreover, the comparison results show that the estimated variations in the attenuation parameters with increasing depth are considerably dependent on utilized velocity models of the medium. Lateral variations in attenuation of seismic waves correlate with the geological and geophysical characteristics of the regions, and attenuation is primarily dependent on the regional seismic activity and regional heat flow. The geological inhomogeneities of the medium and the age of crust consolidation are secondary factors. Our estimations of intrinsic attenuation (Q_i) and scattering attenuation (Q_sc) show that in all the three studied regions, intrinsic attenuation is the major contributor to total attenuation. Our study shows that the characteristics of seismic wave attenuation in the three different rift systems are consistent with each other, and this may suggest that the lithosphere in the zones of these different rift systems has been modified to similar levels.

Modeling of physical and geological properties of a study object is an integral part of geological surveys at each stage. Without a model of physical and geological properties (PhGM) it is impossible to obtain a complete set of reflection indicators of an object in physical fields. The models are useful in solving a wide range of tasks on substantiation of survey methods and routines for interpreting the field data. Generally, a mineral deposit FGM contains the main elements represented by structural–material complexes (SMC) characterized by specific values of geometrical and physical parameters. We attempted at developing an PhGM of the diamond deposits controlled by the Middle Paleozoic trappe magmatism zone of the Vilyui paleoaulacogen. With this goal, in the period from 2002 to 2016, we carried out petrographic, paleomagnetic and geochemical studies of the SMC of the Nyurbinskaya pipe of Nakyn kimberlite field located in the Middle Markha district, West Yakutia. We studied terrigenous–carbonate rocks of the Late Cambrian of the Morkokinskaya and Oldondinskaya suites (Є₃mrk and Є₃–O₁ol, respectively), dolerites of the Vilyui–Markha intrusive complex (βPZ₂vm), autolithic kimberlite breccias of the Nakyn intrusive complex (iPZ₂nk), and sandstones of the Early Jurassic Ukugut suite (J₁uk). Important information was obtained on a wide range of petromagnetic parameters and paleomagnetism of the deposit SMC, elemental chemical composition of ferromagnetic minerals, and other data that can prove useful in discovering promising kimberlite sites in the Vilyui–Markha dike belt. The position of the paleomagnetic pole for the Late Cambrian of the Siberian Platform was clarified: latitude Φ=–35°, longitude Λ=136°, and confidence intervals dp/dm=3.5/6.9°. The poles were estimated for kimberlites (Φ=–11.5°, Λ=111.2°, dp/dm=3.5/7.5°) and pre-pipe basites (Φ=–14.6°, Λ=117.4°, dp/dm=3.7/7.1°). According to the Nyurbinskaya deposit PhGM developed on the basis of the paleomagnetic data, there was the Late Silurian – Early Devonian (S₂–D₁) stage of kimberlite- and trappe formation. The results of our study can enhance the prospects for discovering new primary diamond deposits on the Siberian platform.

The role of rifting in the formation of the recent structure of the Mongolia-Okhotsk orogen is extremely high, but it is still underestimated with regard to flanks of the Dzhagda segment of this orogen. Current researches refer to a combination of physical and chemical processes in the depth of the lithosphere, as well as interactions
between the Izanagi, Eurasian and Pacific plates as explanations of repeated rifting events in East Asia. Upwelling of the asthenosphere due to significant differences in the lithosphere thickness (150–200 km under cratons, and only 100 km under orogenic belts) was viewed as a cause of rifting. It was assumed that rifting was controlled by mantle plumes, volcanism and heat regime. Structures bordering the Mongolia-Okhotsk orogen from north and south were considered as superimposed or marginal troughs. Recent studies have revealed numerous riftogenic Late Mesozoic structures in the Central Asian orogenic belt, which resulted from the collision of the Siberian and North Chinese cratons. New geological survey and geochemical data on volcanites confirmed the riftogenic origin of the Zeya-Uda (or Uda) and Nora-Selemdzha troughs bordering the Mongolia-Okhotsk orogen from north and south, respectively
(Fig. 1, and 2). Geology and geophysics of those troughs has been described. It is noted that riftogenic volcanites formed later in the east than those in the west. The Late Mesozoic rifting is widely manifested in North Eastern Asia across the area exceeding two million square kilometers, from Lake Baikal to the Sikhote-Alin region (west to east) and from the Southern Yakutia basins to North China (north to south). It is evidenced by intra-continental rifts of
various trends, volcanic provinces and extension structures along large strike-slip faults [Renet al., 2002]. The Uda and Nora-Selemdzha marginal troughs located along the Dzhagda segment of the Mongolia-Okhotsk orogen give evidence that compression was replaced by extension in the study area. Rifting structures may be due to physical and chemical processes, the development of plumes [Yarmolyuk et al., 2000], as well as the interaction between the Pacific and Eurasian lithospheric plates. Volcanic activity took place earlier in the west and then propagated to the east due to the shifting of the subduction zone in this direction. This paper analyzes regional and global geological events on the basis of new drilling data and the geochronological dating of volcanites. It describes the Late Mesozoic stage of rifting at the flanks of the Dzhagda segment of the Mongolia-Okhotsk collisional orogen.

The paper describes the neotectonics of the Sakhalin Island and analyzes the latest and recent tectonic stresses in the study area in order to establish their differences in the Amur and Okhotsk microplates, which boundary is confined to the Tym-Poronaisk fault, the largest NS-striking fault in the Central Sakhalin (Fig. 1). Our map of the structural geomorphological features of the study area (Fig. 2) shows three longitudinal zones: the western and eastern uplifts, and the Central Sakhalin basin between the uplifts. In the Southern Sakhalin, neotectonic stresses were studied by a combination of tectonophysical methods and the method of structural geology (Figures 3 to 6, and Table). Our study shows that the regional axes of maximum and minimum compressive principal normal stresses are primarily of the subhorizontal orientations (Fig. 5, Д). In the Northern and Central Sakhalin, neotectonic stresses were reconstructed by the structural geomorphology method. The compression axes are oriented sublatitudinally, with the NE-trending strike in the Northern Sakhalin (Fig. 7, A), and the extension axes are oriented submeridionally; in the Northern Sakhalin, respectively, they are oriented in the NW direction. The results of our study of neotectonic stresses were used to construct a map of recent geodynamics of Sakhalin (Fig. 7, Б), which shows zones differing in the geodynamic settings of the most recent faulting. According to the analysis of the recent tectonic stress with respect to the earthquake focal mechanisms in the period from 1978 to 2015 (Fig. 8), recent stresses dominating in Sakhalin have mainly the sublatitudinal low-angle orientations of the deviatoric compression axis. The submeridional low-angle orientations of the deviatoric extension axes are observed in the Northern Sakhalin and partly in the north of the Southern Sakhalin (see Fig. 8). The high-angle axes of deviatoric extension are typical of the western and central parts of the Southern Sakhalin, and such extension leads to horizontal compression and reverse faulting. In some areas of the recent stress field, the deviatoric axes of compression and extension have unstable orientations. The latitudinal boundaries of such areas are nearly coincident with the boundaries of the zones that differ in the geodynamic settings of the most recent faulting, which means that these areas and zones are reliably identified. The relative inhomogeneity of the neotectonic and recent stress fields in the Southern Sakhalin does not give grounds to distinguish differences in the state of crustal stresses in the areas located on the sides of the Southern Sakhalin fault. As a consequence, a boundary between the Amur and the Okhotsk Plate in the South Sakhalin cannot be drawn along this fault. It is most likely that this boundary coincides with the Western-Sakhalin fault in the southern areas of the study region. Our data on the Central and Northern Sakhalin does not contradict with the conclusion in [Savostin et al., 1982] concerning this boundary.

Rift structures are considered as elements of the composite structural parageneses of deformations in the crust and lithosphere with respect to kinematic types of such deformations. Most of the studied rift systems are associated with shear zones that contain extension faults with normal fault components, as well as strike-slip and compression structures. The regular structural pattern on the Earth surface and its relation to the distribution of the mantle density variations reflect the deformation of the Earth as a triaxial rotating ellipsoid.