The technique of joint analysis of heterogeneous time series of geophysical monitoring systems for the purpose of detecting time intervals and specific periods of bursts of synchronous behavior is presented. The technique is based on the use of the Fourier‐aggregated signals and spectral measures of coherent behavior of multivariate time series, estimated in moving time windows. The article presents results of the analysis of data of underground electrical surveys at stations located in Kamchatka, Altai and Italy; the data were analysed together with torsion pendulum movements in Tula (Russia) and the time series of seismic noise parameters at the Japanese islands for the interval 2012–2015. The analysis identified a number of significant bursts of coherent behavior for these observations, some of which are presumably due to the strong mantle Okhotsk Sea earthquake of 24 May 2013. The coherent behavior of various geophysical fields before and after strong earthquakes is interpreted as a manifestation of the general pattern of increasing synchronization of fluctuations of complex systems at their approach to the rapid changes in their properties. 

We have compiled and analyzed earthquake focal solutions for the territory of Mongolia and its surroundings in order to reveal a spatial variability of stress orientation and stress regimes of the crust. According to the stress inversion results, the SHmax is turning from W-E in the eastern Mongolia to SW-NE in the Gobi Altay and the central Mongolia, and then to S-N in the western part of the region. Comparison with data derived from GPS measurements shows that directions of the strain axes revealed by the geodetic and seismological observations are generally consistent. A contradiction is found for the Bolnai zone where results of GPS estimation indicate the predominance of extension (in the SE-NW direction), whereas earthquake data for the longer period of seismic observations reveal compression. Compression in this zone is mainly due to the Tsetserleg-Bolnai earthquakes contribution; however, a part of the recent data on focal mechanisms fits an extensional stress field with the NNW orientated extension axis. These data are in accordance with some published works which suggest a transtensive field from some structural geology studies in the eastern part of the Bolnai zone.

The paper is supplemented with a list of M≥4.5 earthquake fault plane solutions and unpublished focal mechanisms for some M≤4.5 earthquakes of the northern Mongolia and the southern Baikal region.

The paper presents results of seismogeological studies of active faults bordering the Upper Kerulen basin, one of the largest intermountain basins of the Khentei upland. Morphometric and trenching methods were applied to estimate the main parameters of seismogenic dislocations and associated Holocene palaeoearthquakes (540–2810, 3170–3720, and 7480–9220 years ago). The maximum palaeoearthquake magnitude (7.5) characterizes the seismic capacity of the potential focal area (PFA) confined to the Kerulen fault. The new data show the need to revise the potential seismicity concepts of the southern Khentey area and to make appropriate changes in the general seismic zoning maps. The relationship between the dislocations and the modern topography features, as well as deformation of the subsurface sediments in the studied mine openings give evidence of thrusting under the sub-lateral to north-western subhorizontal compression. 

Cluster analysis is applied for computing stable combinations of geological and geophysical parameters, and areas with such combinations are interpreted as regions that differ in structural and geodynamic features. The shelf areas are distinguished by specific sets and patterns of parameters, including sedimentary cover thickness, tectonic heterogeneity of the basement, heat flow, anomalous magnetic field, and gravity anomalies that reflect the topography of the crust–upper mantle boundary. In the deep oceanic areas, S-wave velocity variations show abnormally ‘cold’ blocks, while the average heat flow values are high. This combination of parameters is typical of transform zones at the junction of the Atlantic and Arctic segments. Superimposed thermal domes are located symmetrically with respect to the axis of the mid-oceanic ridges (MOR). Such domes may occur on the continents located close to MOR. Similar indicators can be revealed along the transition zone to the north of the East Siberian Sea. 

Deep velocity sections of the transition zone from the Siberian platform to the Central Asian mobile belt are constructed by teleseismic tomography and P-receiver function techniques. An array of the dense ancient Siberian craton is identified in the velocity sections with areas of high seismic velocity. In the SSW section MOBAL_2003, the surface boundary of the craton corresponds to the southern margin of the Siberian platform and is nearly vertical to a depth of 120 km. At larger depths, the craton slides almost horizontally underneath the Tunka rift area. At depths from 150 to 250 km, it is in contact with the area under the Khamar-Daban mountain range. In the southeast, according to the SE velocity section PASSCAL_1992 across the South Baikal basin and the Khamar-Daban mountain range, the Siberian craton thickness is reduced from 270 to 150 km at the contact of the Siberian platform with the Baikal folded area. In this contact zone, the upper part of the craton is wedge-shaped and has an angle of about 45° with the ground surface; it completely tapers off at a depth of 150 km to the east of Lake Baikal. The vertical configuration of the southern segment of the Siberian craton, which evolved with time, may determine the nature of the Baikal rifting in the Cenozoic. 

The article provides an overview of experimental studies of charoite and charoite-containing rock formation hypotheses. The authors conducted experiments to clarify charoite and host rocks interaction and study charoite transformation processes at high temperatures. A series of experiments was aimed at improving the substandard charoite samples. The experiments show the formation of polymineral reaction zones due to the contact interaction between charoite and microcline-arfvedsonite lamprophyre. By studying the newly formed phases, the authors reveal the distribution of elements by phases and establish their compositions. It is shown that thermal decomposition of charoite leads to the formation of wollastonite, which amount increases with the temperature increase from 800 to 1000 °C, and heating above 1200 °C leads to the formation of pseudowollastonite. The physicochemical simulation of charoite decomposition under the specified temperatures and pressure shows the following paragenesis: quartz, wollastonite, alkaline pyroxene (aegerine), microcline, rhodonite, and sphene.

The experiments prove the formation of charoite at low temperatures and the lack of silicate melt in the systems studied. The calculated values are consistent with the results of experiments conducted to study the charoite and host rocks interaction, which allows identifying phases potentially co-existing with wollastonite.

Special studies using by the coloring technique were conducted to improve the decorative properties of charoite. The color close to natural high-grade charoite coloration was achieved by keeping the rock samples in the active bright purple dye 4KT solution for 72 hours at a temperature of 70 to 90 °C.

The content of hydrogen in the outer core of the Earth is roughly quantified from the dependence of the density of iron (viewed as the main component of the core) on the amount of hydrogen dissolved in the core, with account of the most likely presence of iron hydrogen in the outer core, and the matter’s density jumps at the boundaries between the outer liquid core and the internal solid core (that is devoid of hydrogen) and the mantle. Estimations for the outer liquid core show that the hydrogen content varies from 0.67 wt. % at the boundary with the solid inner core to 3.04 wt. % at the boundary with the mantle.

Iron occlusion is viewed as the most likely mechanism for the iron–nickel core to capture such a significant amount of hydrogen. Iron occlusion took place at the stage of the young sun when the metallic core emerged in the cooling protoplanetary cloud containing hydrogen in high amounts, and non-volatile hydrogen was accumulated. Absorption (occlusion) of molecular hydrogen was preceded by dissociation of molecules into atoms and ionization of the atoms, as proved by results of studies focused on Fe–H2 system, and hydrogen dissipation was thus prevented. The core matter was subject to gravitational compression at high pressures that contributed to the forced rapprochement of protons and electrons which interaction resulted by the formation of hydrogen atoms. Highly active hydrogen atoms reacted with metals and produced hydrides of iron and nickel, FeH and NiH. While the metallic core and then the silicate mantle were growing and consolidating, the stability of FeH and NiH was maintained due to pressures that were steadily increasing. Later on, due to the impacts of external forces on the Earth, marginal layers at the mantle–core boundary were detached and displaced, pressures decreased in the system, and iron and nickel hydrides were decomposed to produce molecular hydrogen. Consequences of the hydrides transformation into molecular hydrogen are important in terms of petrology, mineralogy and geodynamics. At high temperatures, molecular hydrogen can be involved in redox reactions with iron silicates and carbonaceous gases (CO and CO2), and the synthesis of water becomes possible throughout the entire mantle. It is known that water can significantly reduce the temperature of rock melting, which leads to partial melting of the rocks and pluming in the asthenosphere (in the D” layer) at the bottom of the mantle, and causes the hydrolysis of magnesium silicates, which results in the chemically bound state (hydroxyl ions). Highly ductile hydroxyl-containing magnesium silicates can alter rheological properties of the rocks. A combination of rheologically weak areas in the mantle rocks and the external cosmic effects can cause significant impacts on the tectonic activity and facilitate its manifestation throughout the entire mantle.