The research in Mongolia, carried out by the teachers of the geological faculty of the IGU at different times, is characterized. In 1957-1958. N.A. Florensov and V.P. Solonenko studied the consequences of the Gobi-Altaic earthquake, which occurred on December 4, 1957, and based on the results of these works they opened a new scientific direction - paleoseismogeology. The idea to use seismic dislocations, newly formed during a strong earthquake, to evaluate past seismic events of the territory was eventually supplemented by American paleoseismogeologists by opening seismic ditches and dating events by the method of ¹⁴С. In the 1970s, A.G. Kuznetsov, V.A. Suldin and others participated in the work of the Soviet-Mongolian complex Khubsugul expedition. They assessed the prospects of the territory for phosphorites and bauxites and drew the first geological maps of Prihubsugul, which served as a basis for the work of hydrogeologists, paleoseismogeologists, biologists, soil scientists, chemists and other specialists who participated in the expedition. In 2001-2024, the authors of this paper substantiated in Mongolia the spatial and temporal change in the mantle sources of volcanic rocks of the newest geodynamic stage of the Earth's evolution and linked the origin of lithosphere deformations in the Baikal rift system with the development of processes in the Japan-Baikal geodynamic corridor.

At the Darigang volcanic field of Southeast Mongolia, basaltic and tephritic melts with MgO content of 5-11 wt% and La/Yb ratio of 7-40 - derivatives of the mantle transition region from the asthenosphere to the lithosphere - were mainly erupted in the last 14 Ma. A special role was played by basanitic melts with high MgO content (11-15.8 wt%) and phonotephritic melts with high La/Yb ratio (40-54). Some basanites were erupted in the time interval 10-5 Ma during melting of the residual slab source material with high potential temperature (Tp = 1489 °C), the other part - about 4-3 Ma during melting of the OIB-like source at Tp up to 1423 °C. Phonotephrites were generated at low temperature as a result of degassing of mantle fluids during Quaternary time. Pb-isotopic age estimates of 4.47 and 4.45 billion years ago of protomantle and 3.11 and 2.74 billion years ago of modified mantle, respectively, were obtained for basanite and phonotephrites sources. We suggest that Quaternary degassing of mantle fluids with phonotephritic eruptions at the Dariganga volcanic field is reflected in the generation of the local East Mongolian low-velocity transverse wave anomaly in the upper mantle on the southwestern flank of the Japan-Baikal geodynamic corridor, and that a similar mechanism of Quaternary degassing of mantle fluids resulted in the formation of the local North Baikal low-velocity root structure of the Vitimsky volcanic field in the axial part of the geodynamic corridor. High-Mg rocks (basanites and picrobasalts) of the latter volcanic field have shifted relative to the root structure by 300 km over the last 16 Ma.

The volcanism of the Dachi Zone (Dariganga, Abaga, Dailinor, and Chifeng) fields, extending over 500 km in the border regions of Southeast Mongolia and North China, is reviewed. The conclusion is made about the unified evolution of volcanism that started from the boundary of the North China Craton about 24 Ma with spreading to the north, through the sublatitudinal Solonker suture zone of the PaleoAsian Ocean, which closed in the Late Paleozoic, into the Paleozoic Xing'an block. The involvement of the Solonker Suture Zone in left-lateral movements is established after eruptions that occurred 15-14 Ma in the Dariganga, Abaga, and Daylinor fields, and then after eruptions that occurred about 5 Ma in the northern part of the Chifeng field. The pattern of source change during the evolution of volcanism is estimated from Pb isotopes of volcanic rocks with additional information on Nd isotopes. The sources of volcanic rocks in the southern part of the Dachi zone (Chifeng field) contain a component of the cratonic keel mantle, which is close in age to the craton crust. The development of mantle-crustal cratonization about 2.23 billion years ago under the influence of fluids from the mantle of the Gadean magma ocean that solidified 4.47 billion years ago is suggested. In the sources of volcanic rocks of the northern and central parts of the Dacha zone, older mantle components than the rocks composing the upper part of the crust are determined. The volcanic rocks of the Dariganga field distinguish between protomantle material characterized by geochrones of 4.47 and 4.45 billion years and mantle components evolved about 3.11 billion years ago, including residual slab material. Volcanic rocks of the Abaga and Dailinor fields are characterized by the youngest protolith, corresponding to a geochron of 4.44 billion years.

Researchers of the border regions of Kyrgyzstan, Kazakhstan and China actively discuss two alternative models of correlation of the main structural units of the Tien Shan. Most researchers believe that the structures of the Kyrgyz Middle Tien Shan wedge out in the eastern direction along the Atbashi-Inylchek-Nalata marginal fault. According to the second hypothesis, the structures of the Middle Tien Shan continue within the Nalati Ridge. Nalati Ridge, where they are described as the Chinese Central Tien Shan. Comparative characterization of sedimentary, volcanogenic, intrusive and metamorphic formations of the Paleozoic and Proterozoic of the mentioned regions leads us to the conclusion that the structural units of the Kyrgyz Middle and most of the Northern Tien Shan, including superimposed middle-late Paleozoic troughs, are not traced in the territory of China, but are successively sheared along the system of coulically articulating shears, united by us in the Frontal Tianshan Right Shear (FTLS). And only the northern segment of the Issykkul terrane can be considered as an analog of the Chinese Central Tien Shan, displaced along the MTFS to the northwest at a distance of at least 80 km. Geological complexes are sheared along the MTFS similar to the way oblique boundaries of converging lithospheric plates are subjected to tectonic erosion.

The paper presents some results of studying various samples of slip mirrors collected during expeditions from different-age seismic dislocations in Pribaikalie and Mongolia, including from deep segments of seismically active fault zones exhumed to the Earth's surface. Petrochemical and thermodynamic processes in paleoearthquake centers that occurred hundreds of millions of years ago in deep segments of faults were analyzed using methods of petrophysical study of the processes of hydrothermal-metasomatic transformation of fractured rock matter in slip mirrors. The data of in-situ and laboratory experiments conducted to study the mechanisms of formation of slip mirrors and tectonic pseudotachylytes, which arose during frictional heating of rocks at the moments of high-velocity displacements in faults, are also presented. The analysis of the totality of new data obtained indicates that a comprehensive study of slip mirrors allows us to supplement the existing ideas about seismogeological conditions of paleoearthquake sources in deep segments of active faults, and also contributes to the creation of new models of earthquake sources and the development of earthquake prediction methods. In the applied aspect, the obtained fundamental results become important for seismic hazard assessments and development of new methods for its reduction.

The composition of pebbles and sandy filler of the pebble pack completing the section of the Lower Pliocene Buguldean alluvium horizon in the middle part of the Pra-Manzurka valley is compared with the composition of pebbles and sandy cement of Middle Jurassic conglomerates of the Lower Kotov subformation from outcrops of the Angaro-Kotinsky depression in the southeastern part of the Irkutsk coal basin. Partial similarity of petrogenic oxide and trace element contents in trachydacites and rhyolites of pebbles from Pliocene and Jurassic sediments is established. The difference in the contents of petrogenic oxides and trace elements in the sandy filler of the lower and upper layers of the pebble pack of the Pra-Manzurka valley is determined and the conclusion is made about the difference in their sources. It is suggested that the convergence of the composition of the sandy fill of the lower layers of the Pliocene gravel pack with the composition of trachidacite-rhyolite pebbles and the composition of sandy cement of the Middle Jurassic conglomerates may reflect the erosion of clastic material of the Middle Jurassic conglomerates and its removal to the middle part of the Pra-Manzurka valley during the initial phase of the Primorsky Ridge uplift. The presence of Th/Co anomaly in the lower layers of the gravel pack, which is not characteristic of Jurassic conglomerates, indicates the formation of gravels from an additional source of clastic material.

Conglomerates exposed on the northwestern shore of Lake Baikal, in the areas of Bolshiye Kotov and Listvyanka, belong, according to paleontological data, to the upper part of the section of the southeastern part of the Irkutsk Basin (Angara-Kotinsky Depression) and are considered to be part of the lower sub-formation of the Kotov Formation, dated to the upper part of the Aalenian Stage of the Middle Jurassic (174-170 Ma). To identify the source of clastic material of conglomerates, the contents of petrogenic oxides and trace elements are determined, and slits of volcanic rock pebbles are examined. Five groups of trachidacite-rhyolite pebbles of plumasite composition are identified in the first outcrop and a group similar in composition to the main Bolshekotov group in the second outcrop. The difference between pebbles of conglomerates of the upper part of the section of the Angaro-Kotinsky depression and pebbles of alkaline effusives of acidic and medium composition of the lower and middle parts of the section is outlined. The composition of pebbles of the Upper Kotinsky subformation is assumed to be similar to the composition of Middle Jurassic volcanic and subvolcanic rocks of Transbaikalia. Their origin is assumed to be from three sources: 1) the nearest - an unknown Middle Jurassic volcano buried under the Cenozoic sediments of the South Baikal Depression, in the suture zone of the Siberian paleocontinent, 2) the middle distant (250-500 km) - Middle Jurassic volcanic-plutonic complexes of the Dzhida-Vitim fault zone, and 3) the more distant - the Mongolian-Okhotsk fault zone.

The paper deals with the structural and petrological evolution of one of the many gabbroic massifs of the Southern Pribaikalsky region - Snezhninsky, located near the river of the same name, characterized by the most typical structural-metamorphic paragenesis: comfort with layering of host rocks, located in a steep inverted wing of asymmetric folds of latitudinal strike with horizontal hinges and north-tilted axial planes. The wing of the fold and the lying southern side of the massif are complicated by a longitudinal oblique strike-slip fault with a thick zone of tectonites. The northwestern end of the massif is complicated by a northeastern strike-slip thrust. The massif dips to a depth of 4-5 km and is cut by another northwest strike-slip fault. The internal structure of the massif is characterized by a rather monotonous development of minor structural forms: magma flow structures emphasized by the elongation of flat xenoliths, asymmetric folds of the right pattern in plan, gradual interchanges between all varieties of rocks composing the massif, indicating a significant heating of all rocks during their formation and assimilation.