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Distribution of hydrogen and carbon isotopes (D/H and ¹³C/¹²C) in the microbial systems CH₄-H₂O and CH₄-CO₂ was studied in different world's regions. According to the distribution of these isotopes in the above systems, two types of microbial methane are recognized in the Earth's crust: (1) resulting from CO₂ reduction and (2) produced through acetate fermentation. In the case of methane 1, the biologic distribution of hydrogen and carbon isotopes in the above systems corresponds to the thermodynamic isotope exchange equilibrium at a given temperature of the methane genesis medium. In the case of methane 2, the same systems show mainly a nonequilibrium distribution of these isotopes. We have revealed a linear relationship between the isotopic compositions of CH₄, H₂O, and CO₂: δD - CH₄ = α _D ^b δD - H₂ O + b and δ¹³ C - CH₄ = α _C ^b δ¹³ C - CO₂ + d, where α _D ^b

In 1996 the Volgian Stage was divided into the Jurassic and Cretaceous units, removed from the Geological Time Scale, and substituted by the Tithonian Stage according to the guidelines of the Interdepartmental Stratigraphic Committee of the Russian Federation (ISC RF). Consequently, the Upper Volgian Substage including three zones (five subzones) was placed into the Berriasian Stage (the Cretaceous) proceeding from ammonite fauna, and the Cretaceous lower boundary was defined by the base of the Kachpurites fulgens Zone. Some stratigraphers, however, contested that decision and suggested to restore the former status of the Volgian Stage. Their idea has been validated by magnetostratigraphic studies carried out in 2003 in Jurassic-Cretaceous boundary strata in the Nordvik Peninsula (the Laptev Sea), which bear the most complete record of Boreal deposition and biostratigraphy. The new data prove that the Volgian Stage, in its nearly full stratigraphic volume, rather belongs to the Jurassic period.

We report new radiocarbon ages, pollen stratigraphy, and botanical composition of an organic sediment sequence from mountains along the northwestern side of Lake Baikal. The calendar age of the peat is ca. 9.5 kyr BP. The pollen spectra between 9.5 and 8.5 kyr ago show vegetation consisting mostly of open larch and spruce-larch forests with minor birch. The interval from 7.5 to 6.8 kyr BP is marked by broad fir spread confirmed also by the peat botanical composition. The climate inferred for the period of fir dominance combines mild winters, cool summers, thick snow cover, and abundant moisture, apparently due to more intense North Atlantic air transport. Fir percentages decrease dramatically after 6.8 kyr BP, when pines begin to spread in the Baikal watershed. The peat record bears imprint of North Atlantic cooling events identified as intervals of ice-rafted detritus deposition and low surface water temperatures. The new data allow a better insight into the regional climate and landscapes, and the reliable age model provides regional and inter-regional correlations of global change events.

The problem of an elastic stress field in a rotating medium is formulated and solved analytically within the limits of the classical theory of elasticity with a symmetrical stress tensor. This is a rotation elastic field of action at a distance. There are two specific types of elastic waves with a moment in rotating media: solitons and excitons, or rotation waves. The soliton solutions to the wave equation represent waves of global earthquake migration (slow tectonic waves) which are no faster than ~1 cm/s, i.e., approach the migration velocity of large and great earthquakes (M > 7.5). The exciton solutions correspond to waves of local migration of foreshocks and aftershocks in earthquake sources (fast tectonic waves) and have their maximum velocity comparable to faulting rate and/or to S-wave velocities.

We have designed a frequency-domain electromagnetic induction sensor for imaging the distribution of electrical conductivity of soils in civil engineering applications. The device implements the ultimate technical feasibility of measuring harmonic signals on the ground surface. Digital recording and narrow bandpass filtering of synchronous detection allows a sufficient measurement accuracy for ~1 μV signals and suppression of power-line noise of more than 100 dB. We suggest practical methods for investigating the characteristics of the sensor and estimating its measurement accuracy.

This paper reviews available the mantle plume models and formulates seven questions, which can be solved using geological and geochemical data in terms of the thermochemical plume model.
The main features of thermochemical plumes, including calculated plume parameters, are presented. It has been estimated how the power of a plume depends on water concentration in melt at variable melt portions and diffusion coefficients (Lewis numbers). A correlation between the latter and temperature drop at the base of a plume has been shown.
The obtained plume parameters are compared with model plume localities, such as the Hawaiian and East African plumes, Siberian and Emeishan flood basalts, etc. Based on the oceanic plate movement pattern and He, Os, and Sr isotope data, the Hawaiian plume was proved to be generated within the D₂ lower mantle layer; the diameter of the plume channel is about 100 km, the plume channel rotated and migrated to 100-200 km every 2 Ma; the plume power is about 3 · 10⁸ kW, changing each 15 Ma. The reconstruction of complex core material-plume melts and Layer C-asthenosphere interactions is possible only by isotopic data and primary olivine composition.
The plume model was applied to large igneous provinces (Siberian, Emeishan, and Ontong Java LIPs) using detailed mechanisms of plume head interaction with the lithosphere. Taking into account the similar age and evolution of the Tunguska syncline (Siberian LIP) and West Siberia, the plume-lithosphere interactions are deduced from the relationships between sedimentary and magmatic units, different modes of rifting, and variations of Sr and Nd isotopes.

The paper reports data on the age, composition, and geodynamic environments of Permian ultramafic-mafic complexes in the Zaisan-Gobi zone in the eastern Gobi-Tien Shan rift belt. The synchronous formation of these complexes with Early Permian lava alkali and tholeiitic basalts discovered beneath the cover of the Tarim and Junggar platform blocks suggests that they are derivates of the Tarim plume related to the Permo-Triassic Siberian superplume. This is evidenced from the composition and metallogeny of the complexes similar to those of magnesian trap intrusions on the western periphery of the Siberian Platform.
In the area of influence of the Tarim plume, including the Zaisan-Gobi zone and other structures of the Gobi-Tien Shan belt, diverse Cu-Ni-PGE, Ni-Co-As, Au-Hg, Cu-Mo, and ore deposits related to plume magmatism formed. Their composition, formation conditions, and relationship with magmatism are discussed.

New structural and petrological data have been obtained for the zone of Siberia-Kazakhstan oblique collision for Permian time. In terms of classical tectonics, the area coincides with the Zaisan folded area produced by closure of the Char paleo-ocean in the Late Carboniferous. However, the extent, structure, and composition of magmatism at the Carboniferous-Permian (280 ± 10 Ma) and Permian-Triassic (250 ± 5 Ma) boundaries require an active control from Morgan-type lower mantle plumes (Tarim and Siberian plumes). Structure formation in the lithosphere and heat sources of magmatism have been simulated in a 3D model including lithospheric strain rates (with regard to viscosity layering) and subcontinental upper mantle convection. According to our model, heat supply from slab break-off and/or delamination of lithosphere is insufficient to maintain large-scale mantle-crustal magmatism in the case of oblique collision between 80-100 km thick plates (

We have shown that the occurrences of Permo-Triassic magmatism in northern Vietnam compose the southwestern and southeastern flanks of the Emeishan large igneous province, shifted along the large-amplitude Ailao Shan-Red River shear zone. Based on new geochronological (U-Pb and Ar/Ar) data, two stages of magmatism related to the Emeishan plume have been recognized. At the first, Permian, stage (260 Ma), abundant picritoids of the Song Da and Song Hien zones formed, and at the second, gabbro-syenite and gabbro-monzodiorite associations of the Lo Gam zone, layered peridotite-gabbro massifs of the Nui Chua complex, high-alumina granites of the Phia Bioc complex, and basalt-rhyolite association of the Song Hien zone were produced. The metallogenic specialization of the Permo-Triassic magmatism of northern Vietnam is considered.

We investigate the dynamics of multilevel subcontinental melting beneath a lithosphere of variable thickness as a model simulating generation of melts that produced flood basalt in the Siberian Trap province. The inferred sequence of volcanic events correlates with upper mantle decompression melting above hotspots and related conductive melting of metasomatized depleted lithosphere. Numerical experiments show that complex mafic magmatic systems of this kind are at least two-stage with a zone of decompression melting in upwelling mantle flow and a sub-Moho lithospheric melting region; the shallower lithospheric melting region can be disconnected from the mantle zone of decompression melting along the edges of the magmatic system; the lithospheric melting region has a particular layered structure with its top at a depth of 60-70 km and a maximum size exceeding the length of the erupted lava field; mafic melts produced at different levels of the system have different compositions.