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EPR spectrscopy was used to study specific features of distribution of paramagnetic admixtures in endogenous carbonates formed in the zones of contact of trap complex with deposits of the Siberian Platform cover. It was established that the main paramagnetic centers in the studied samples are: a) ions Mn²⁺, isomorphously replacing Ca²⁺ and Mg²⁺, b) ions Fe³⁺, forming oxide or hydroxide clusters 100-1000 and more in size, and c) radiation centers, originated from natural ionizing radiation. Using indicator features of spectra, it was established that carbonates from magnesian-skarn associations are a solid solution of calcite with dolomite and ankerite. Compared with carbonatites, calcites from the contacts with traps have a lower Fe content and low concentrations of Fe³⁺ clusters. Radiation centers were detected in Fe-free calcites accompanying apatite. The number of paramagnetic ions Mn²⁺ decreases in low-temperature generations of calcite. All genetic groups have a tendency to replacement of structurally inhomogeneous high-temperature solid solutions of carbonates by stoichiometric calcites, dolomites, ankerites, and siderites.

The age of ophiolite plagiogranites from the Khan-Taishiri ophiolite complex, western Mongolia, was determined by the U-Pb zircon method as 568.1 4.0 Ma. This complex is a rare fragment of the ancient Central Asian blocks where real geological relationships within large tectonic slabs making up the ridge have been established between all ophiolite sequences but ultrabasic rocks: pyroxenite and gabbro from banded sequence, basic rocks of dike complex, dolerite sills, basic pillow lava, and deep-water clay-siliceous sediments.
The Neoproterozoic age of the Khan-Taishiri ophiolite complex suggests the presence of a Vendian island-arc system within the Central Asian Mobile Belt. The model for this system was described for the first time by L. P. Zonenshain and O. Tomurtogoo on geologic objects of western Mongolia from Dzavhan River to northern slopes of the Mongolian Altai Ridge (Dzavhan, Gobi-ALtai, Khan-Taishiri, Naran, Ulan-Shandian, and Kuroi subzones). This system obviously included the Daribi ophiolites of western Mongolia; the Agardag and Shishkhid ophiolites of Tuva; the Dzhida and Ol'khon fragments of island-arc system; the belt of subductional layered massifs of Northern Baikal and eastern frame of the Muya Block; the Naran, Eastern Sangilen, Southern Khamar-Daban, OL'lhon, and Bodaibo fragments of sedimentary basin; the Dzavhan, Hovsgol-Bokson, Western Baikal, and Baikal-Patom shelf fragments. Ocean lithosphere was represented by Bayan-Khongor ophiolites.

The effect of vibrations (storm microseisms) in Lake Baikal on seismicity in its shore zone is investigated by comparing the number of earthquakes that occur in winter in the absence of waves and vibration to that during the time of strongest storms. Observations over ten recent years show that the number of small and medium earthquakes (6 K 13) in "quiet" time is nearly twice as high as that during storms, which indicates the influence of storm vibrations on the seismicity. The observed vibrations have been analyzed in terms of their spectra, attenuation, amplitude, and radius of influence.

We present original precision data on the chemical and trace-element (Li, Rb, Cs, Ba, Sr, Pb, Zn, Sn, Co, Ni, Cr, V, Cu, Sc, Mo, W, Nb, Zr, Hf, Th, U, REE, and Y) compositions of igneous rocks of the Tundak sill (Northern Transbaikalia) - picroteshenites, meso- and leucoteshenites, and analcime syenites. These rocks are shown to have formed through intrachamber crystallization differentiation of the same teshenite magma within the sill. The K-Ar age of the teshenites is 118.83 3.56 Ma.
The Sr isotope characteristics of the sill rocks and their hosted minerals disagree with the isochron model. We have established that the dispersion of Sr isotope compositions is caused mainly by postmagmatic alterations of these rocks rather than by the isotopic heterogeneity of the initial melt. The (87Sr/86Sr)₀ value of this melt (0.7053-0.7056) does not rule out the presence of admixed assimilated crustal matter in it.
Geological and geochemical analyses showed a great similarity of the North Transbaikalian and Late Cretaceous West Transbaikalian teshenites. We have also established that the study teshenites are close in age and composition to trachybasalts that effused in both regions at the earlier stages of the Late Mesozoic taphrogenic volcanism. We propose a genetic model for the formation of basaltoid melts of both types (teshenite and trachybasaltic) from the same mantle source. The model implies that the compositional differences between these types are related to the long evolution of parental magmas and admits mixing of deeply differentiated and primitive melts in intermediate magma chambers.

The REE composition of uraniferous alluvial deposits in the Malinovka paleovalley of the Chulym-Yenisei depression is studied. The contents of elements are determined by the INAA and X-ray fluorescent methods and by emission and X-ray spectroscopies. The minerals are identified by X-ray, luminescent, and laser analyses.
According to clarke of concentration, the elements follow the sequence: Se (3600), U (250), W (185), As (47), Mo (13), V (6.3), Hf (2.1), Ge (1.8), Y (1.3), Sc (1.2), Zr (1.2), REE (0.9), and Th (0.4). Such elements as U, Mo, Se, V, Hf, W, As, and Y are characterized by an extremely uneven distribution in the deposits (V > 70%). The ore-bearing zone shows three types of elevated concentrations of elements: primary clastogene (W, Ge), primary sorption-biogenic (U, Se, Mo, V, As), and secondary redeposited infiltrogenic (elements of the first two types plus Hf, Sc, and REE). The high content of W is explained by its supply from primary deposits of the Altai-Sayan region, and the high content of Ge is due to the presence of fragments of Ge-bearing coals.

The Oka plateau exists as a moderately elevated (2400 m) intermontane area bounded by the major East Sayan dome, the Main Sayan Fault, and the Baikal Rift system, in the zone of the rift strike break. The plateau, which has a block structure, and its surroundings show specific features of recent geodynamics, including seismicity and distribution of Cenozoic basalts. These specific features are related to the position of the region over a hotspot swell along 100 E, which corresponds to a column of low-density material connecting a sublithospheric asthenolith with the lower mantle.

Kerogen of the dispersed organic matter (DOM) of the Lower Toarcian Togur Formation of the West Siberian Plate has been investigated by various methods: elemental analysis, analysis of the isotopic composition of organic carbon, and pyrolysis. It is shown that the kerogen composition depends of the facies settings of sedimentation. Two groups of DOM kerogen samples have been recognized. One of them formed under coastal conditions, and the other, in fresh-water basins with a considerable inwash of terrigenous matter. The kerogen of the first group is more aliphatic, yields more volatile compounds, has an elevated hydrogen index (HI 250 mg HC/g C_org), and is depleted in ¹³C (_av =

The composition of minerals and rocks of the Arban granulite massif has been studied. The massif is a tectonic block among stratified volcanometasedimentary deposits of the Onot greenstone belt (Sharyzhalgai protrusion of the Siberian Platform). According to mineral and chemical compositions two types of basic granulites are recognized: leucocratic, close in contents of major and trace elements to low-titanium tholeiitic basalts, and melanocratic, depleted in SiO₂, Na₂O, Rb, Ba, Sr, and LREE and enriched in Fe₂O₃, Ti, Nb, HREE, Y, and Sc (compared with the leucocratic granulites) and compositionally similar to restite equilibrated with tonalite melt. Acid plagiogranulites are compositionally close to high-alumina tonalite-trondjemites forming from a metabasic source at P 12

We report the first U-Pb dates for allochthone hypersthene granites – kuzeevites – from the Angara-Kan protrusion of the Yenisei Range. The obtained age 1734 4 Ma marks the termination of folding and metamorphism under the PT-conditions of granulite facies which determined the internal structure of the Kan crystalline rocks.

The Mongolo-Transbaikalian alkaline-granitoid province is more than 2000 km long and includes more than 350 plutons of alkali granites and syenites and numerous fields of volcanic derivates of alkaline-granitic magmas. Formation of the major volume of acid magmas in the province was considered to take place continuously from early Permian to early Triassic, about 280-240 Ma ago. The Rb-Sr and Sm-Nd isotope studies of the rocks of the typical trachybasalt-comendite bimodal series of the Tsagan-Hurtei Range showed its Late Triassic age, 2125 Ma. The isotopic Nd-Sm characteristics (_Nd(T) = + 1.9+2.8 both in trachybasalts and comendites) and a regular distribution of REE in basic and acid rocks of the series suggest affinity of these rocks and possible genetic relations of alkaline-granite melts with trachybasaltic magmas. Data on high-temperature homogenization of melt inclusions in phenocrysts of quartz from comendites (to 1100 ^oC) and on the presence of no less than 1 wt.% H₂O and F in these inclusions indicate considerable depths of magma generation or injections of high-temperature basaltic melts into acid magma chambers.