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We studied interstitial glasses and melt inclusions in minerals of peridotites from Pliocene basanites of the Vitim volcanic field, Dzhilinda River basin. The glasses can be divided into two groups: A and B. The glasses of group A resulted from deep-level partial melting of mantle, and those of group B are the interaction products of the host basanite melt and peridotites. The heated glasses of group A in xenolith minerals are compositionally similar to experimental and model partial (<10%) melts of peridotites obtained at 10 kbar. They contain (wt.%): SiO₂ = 51-56, TiO₂ = 0.5-0.6, Al₂O₃ = 12-16, Cr₂O₃ = 0-0.5, FeO = 2-4, MgO = 7-10, CaO = 6-12, Na₂O = 3-7, and K₂O < 1.5. Glasses from Ti-rich peridotites contain 1.9-3.5 wt.% TiO₂. Glasses of group B have similar contents of SiO₂, Al₂O₃, and Na₂O, high TiO₂ and K₂O contents, and low Mg-number. Interstitial glasses of this group are abnormally enriched in K₂O (up to 10 wt.%). Glasses in spinel harzburgite are SiO₂-richest (up to 71 wt.%); their alkali concentration decreases with increasing SiO₂ content. These data are consistent with the model for the reaction of xenolith orthopyroxene with basaltic (or hybride) melt, producing olivine and medium- and high-silica glass. The regular compositional variations of olivine microlites with high Mg-number (up to 94) and coexisting glass suggest that they are in equilibrium. The coefficients of Fe/Mg partition between them are 0.25-0.33.

The available data show that the hydrogeology of the Nyurol'ka basin is characterized by widespread connate waters, in places diluted by ancient percolating waters. This basin has vertical hydrodynamic and hydrogeochemical zoning. Combined with elision, this favors oil and gas formation. We have established that the Lower-Middle Jurassic sediments are fed by their own saline waters as well as by the waters of Paleozoic and Upper Jurassic complexes at the sites where permeable sediments exist. This explains mixing of different genetic types of waters in the sediments. We have first revealed the existence of vertical water cross-flows between aquiferous complexes, which generally does not disturb their hydrodynamic isolation.

This is the second paper on the history of multiwave seismic exploration in Russia in the past fifty years. It considers the behavior of compressional, shear, and converted waves and their synthetic interpretation. Multiwave seismic exploration is analyzed in application to various geological targets, including petroleum prospecting.

A new teleseismic tomography approach (RR-R scheme), based on joint processing of differential travel times of P or S refracted rays and corresponding PP or SS rays with bounce points in a selected area, allows three-dimensional velocity images of upper mantle in aseismic regions with poor seismological coverage. The approach makes it possible to avoid the difficulty of source and station corrections which cause problems in teleseismic tomography. The RR-R scheme has been applied to more than 10,000 ray pairs from the ISC database to investigate a large territory from the North Arctic Ocean to northern China and Mongolia. Inversion was carried out in several separate blocks that cover the territory, and velocity anomalies were computed in grid nodes distributed in the 3D region according to ray density. The results from different blocks were synthesized into general maps and cross sections. The lithospheric structure imaged by the inversion includes positive P-wave velocity anomalies associated with the Precambrian Siberian craton and Tuva, negative anomalies corresponding to the thin lithosphere of the West Siberian Plate, and an intense negative anomaly beneath the Hangayn mountains, possibly, produced by a mantle plume.

Some stratigrapho-paleogeographic discrepancies have been removed from the interpretation of spatial-temporal relationship between leading factors of morpholithogenesis in the Late Pleistocene of West Siberia. New data obtained from mammoth remains indicate that there was no ice-dammed basin on the West Siberian Plain in the Sartan time. A hypothesis has been formulated that the Karga marine deposits occur in overdeepened lows, tens of meters below the paleolevel of the ocean, which formed when the ice-dammed waters broke the ice dam to run northward. This refines the configuration of the Karga marine transgression whose deposits are mapped on the north of West Siberia in accordance with a recent stratigraphic scheme. The Late Pleistocene and Holocene of West Siberia include relatively long stages of stable and metastable ecogeological settings alternating with short epochs of drastically contrasting transformations of paleolandscapes.

The paper presents a historic account of multiwave seismic exploration in Russia for the past fifty years: the origin of the method, its development in different institutions, and principal results concerning excitation and recording of shear and converted waves.

Evolution, space and time dynamics of stresses, geometry of basins, and other particular features of the Baikal rift can be explained in the context of stress changes associated with rifting initiation. Rifting may have been triggered by local heating of the 70 km thick lithosphere from a sublithospheric mantle plume. The impact of heating necessary to initiate extension has been estimated in terms of a thermoelastic loading model for rift-orthogonal plane strain. Finite element simulation using the NASTRAN software reveals a mosaic stress field in heating lithosphere. The existence of different stress zones may account for the rift asymmetry, initiation and/or development of major faults, horizontal layering of lithosphere, attenuated crust, etc. The plane strain finite element model of lithosphere subjected to thermal loading provides a sound clue to understanding the driving mechanism for rift formation.

The Tongulak metamorphic complex lies in southeastern Gorny Altai, in the Bashkaus-Kubadru interfluve. Four zones have been recognized in its composition: chloritic (on the periphery), cordieritic, sillimanitic, and staurolite-free. The metamorphic zoning is symmetrical, with a general width of 13-15 km. Conditions of metamorphism are estimated to have been 500-700

A detailed petrological study has been given to high-alumina ferriferous hornfelses characterized by the development of mineral associations (Cld+Bt, Cld+Bt+And, and Crd+Grt+Ms), quite rare for contact metamorphism. The sequence and stability of the observed parageneses were thoroughly analyzed in terms of the Harte-Hudson, Spear-Cheney, and Powell-Holland petrogenetic grids. It has been shown that in the contact aureole of the Ayakhta Massif: (1) the formation of chloritoid atypical of thermal metamorphism and the stability of rare parageneses (Cld+Bt and Cld+And+Bt) are explained by a rare combination of appropriate pressure (3 kbar) with a specific type of rocks enriched in both Al and Fe; (2) the appearance of the Grt+Crd+Ms paragenesis is caused by specific chemical compositions of Mn-enriched garnet and high-Al high-Fe rocks; (3) the development of Crd-And parageneses and staurolite-free associations at the intermediate steps of contact metamorphism is explained by the simultaneous expansion of the Grt+Chl field with participation of Mn-garnets and narrowing, up to complete disappearance, of the St+Bt stability field; (4) the sequence of the observed parageneses and reactions in high-Al Fe-rich hornfelses of the Ayakhta aureole is in agreement with the Spear-Cheney thermodynamic petrogenetic grid.

A brief 19-17 Ma episode that marks the onset of magmatism has been dated from Rb-Sr isochron and ⁴⁰Ar/³⁹Ar geochronology of lavas from the Rungwe volcanic province. According to ⁴⁰Ar/³⁹Ar and preliminary K-Ar geochronology, volcanism and rifting in East Africa initiated in the Eocene in the Turkana depression between the Ethiopian and East African plateaus. A strong thermal impact from a mantle plume impinged on the lithosphere beneath the Ethiopian plateau caused numerous volcanic eruptions along the central segment of the Ethiopian rift about 30 Ma ago and sublithospheric thermal erosion on the periphery of the East African plateau, since 23 Ma in the Kenya rift and since 19 Ma in the Western rift.