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We report reprocessed aftershock data from the

The three-dimensional velocity structure of upper crust in the epicentral area of the Chuya earthquake was imaged using traveltimes of P and S waves from aftershocks. The northeastern part of the area including the territory of the Chagan-Uzun block and the Kurai and Chuya intermontane basins corresponds to a zone of high S velocities and Poisson's ratios. The southwestern part is a zone of relatively low P velocities and Poisson's ratios within the North Chuya ridge. S velocities are rather uniformly distributed over the area and show no significant anomalies. The main shock and the aftershocks, which are aligned in the northwestern direction, originated at the edge of the revealed anomalous P velocity zone.

The stress field in the upper crust of the Baikal rift produced by the system of large faults, active in the Cenozoic, has been simulated in laboratory optical models and compared to the seismicity pattern. Different loading regimes in three sets of models provided extension strain in the central part of the rift and corresponded to impacts from different external forces. Stress distributions in the three model sets correlated to the superposed fault pattern showed features of similarity and difference. The distribution of large earthquakes in the Baikal rift can be accounted for in terms of the interplay of passive and active rifting mechanisms.

The geologic structure of shungite deposits in Karelia and the composition of shungites are considered. Modern models for the genesis of these rocks are presented. The specific features of the rocks are analyzed in terms of a recently proposed model for the genesis and evolution of shungites, implying the formation of soot during the combustion of deep-seated methane under oxygen deficiency conditions. It is concluded that the model is constructive and does not contradict factual data.

In this paper we generalize the data obtained for the Kuznetsk Basin traps studied over many years. A rich collection of samples from the Permian and Triassic igneous/sedimentary succession of the Kuznetsk Basin was analyzed. As a result, directions of characteristic remanent magnetization have been established ( D_s = 227.1, I_s = -64.3, α₉₅ = 2.8). Also, the paleomagnetic pole has been located accurately enough to be used in paleotectonic reconstructions. The Permian-Triassic age of the characteristic component of magnetization has been confirmed by fold and baked-contact tests. Comparative analysis of the magnetic zoning record in the sections of traps of the Kuznetsk Basin, northern Siberian Platform and West Siberian Plate shows that the processes of intraplate magmatism were mutually related in these areas about the time of the Permian-Triassic transition. Systematization of the obtained and available paleomagnetic data shows that the trap magmatism in the Kuznetsk Basin, as compared with the rest of Siberia, was an extremely short-term event. The entire section corresponds to the initial stage of the intraplate magmatic activity in the Siberian region, with their formation lasting no more than 1 Myr. The position of the calculated paleomagnetic pole (PLat = 60.0, PLong = 172.7, α₉₅ = 4.0) and the orientation of the Permo-Triassic latitudes of the Kuznetsk Basin have a considerable angular deviation from those of the Siberian Platform (PLat = 49.0, PLong = 151.6, α₉₅ = 5.0). The angular distance makes about 24

The olivines in dunites and harzburgites of ophiolite massifs in the Baikal-Muya belt are characterized by a great diversity of deformations with a regular change of microstructural types: protogranular, mesogranular, porphyroclastic, porphyrolath, mosaic, mosaic-lath, and parquet-like. Petrofabrics of the petro- and mesogranular types have been formed by the translation slip and static annealing recrystallization at 1100-1300

Using the ⁴⁰Ar/³⁹Ar method, an Early Cambrian age has been established for granodiorites stripped in the bottom-hole zone (4824-5005 m) of Vezdekhodnaya BH-4 (Tomsk Region) in the southeast of the West Siberian geosyneclise. Primitive crust of weathering is developed on the granodiorites. The rocks are overlain by gritstones of sedimentary nature. The results obtained suggest a short time gap between the intrusion of the granodiorites into volcanosedimentary strata and the first effusion of the overlying submarine basalts.

Study was given to granitoids of the Kitoi complex on the southern flank of the Siberian craton (Sharyzhalgai uplift). The granitoids are regarded as syntectonic in accordance with their regional occurrence, geology, and structure. Their U-Pb zircon age is 2532 ± 12 Ma. Petrological, geochemical, and isotopic data obtained suggest that the Kitoi granitoids might have been produced from the enclosing metamorphosed sedimentary rocks. The intrusion of these granitoids proceeded synchronously with the formation of the Late Archean Urik-Kitoi collision zone, which originated during the accretion of the Irkut and Oka superterranes of the Sharyzhalgai uplift. Granitoids of the Kitoi complex and coeval granulites of the Urik-Kitoi collision zone are indicators of Late Archean collision processes running within the Sharyzhalgai uplift. These collision and accretion processes correlate well with similar events that took place in the Aldan Shield and in some ancient cratons. On a global scale, these events proceeded during the formation of the Late Archean Pangea 0 supercontinent (Arctic).

By the example of West Siberia, it is shown that paleocarpology permits fractional division of continental Cenozoic strata in closed areas, impossible with other paleontological methods. Ten biostratigraphic zones have been recognized in the studied Upper Lutetian-Aquitanian stratigraphic section.

Structure of the deposits and basement beneath the South basin of Lake Baikal is investigated down to a depth of 14 km on a profile about 100 km long. Ray tracing modeling of refracted and reflected waves is applied. A discrepancy between the observed and calculated wave traveltimes does not exceed 0.05-0.1 s for the parameters of cross section. In addition, the reliability of the sedimentary cover structure is confirmed by similar synthetic and observed record sections. Four layers with individual characteristics are allocated, divided by seismic boundaries with rather sharp differences of velocity. Velocity changes with depth on the given profile are similar to results of seismic observations in the Selenga depression, in deposits of the West Siberian Plate, Siberian craton and Vilyui basin. It is possible to assume that the sedimentary cover up to 10-12 km thick hosts not only Cenozoic and Mesozoic but also Paleozoic rocks. Therefore it is possible that the age of the South basin of Lake Baikal is more ancient than the Cenozoic-Mesozoic.