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Russian Geology and Geophysics

2008 year, number 5

The Oneka intrusive complex: a new structural type of large-scale manifestations of intrusive trap magmatism on the Siberian Platform

Yu.R. Vasil'ev a , S.N. Prusskayab, M.P. Mazurov c , A.Ya. Medvedev d , A.I. Al'mukhamedov d , M.P. Goraa
a Institute of Geology and Mineralogy, Siberian Branch of the RAS, 3 prosp. Akad. Koptyuga, Novosibirsk, 630090, Russia
b Institute of Mining, Geology, and Geotechnology, Siberian Federal University, 35 prosp. Krasnoyarskii Rabochii, Krasnoyarsk, 660025, Russia
c Novosibirsk State University, 2 ul. Pirogova, Novosibirsk, 630090, Russia
d Institute of Geochemistry, Siberian Branch of the RAS, 1a ul. Favorskogo, Irkutsk, 664033, Russia
Keywords: Intrusive traps; structural type; large-scale complex; Siberian Platform
Pages: 279-309

Abstract >>
The Oneka intrusive complex, recognized on prospecting for hydrocarbons in the western Siberian Platform, in the northern half of the Bakhta megablock (Tunguska syneclise), holds a special position among the known and new large-scale manifestations of intrusive trap magmatism. During the process, original data on the distribution of traps in the 4.2 km thick platform cover were obtained. Diverse in morphology and size, the intrusions are of the same genesis, composition, and character of intrachamber differentiation and form a

Melt inclusions in eclogite garnet: experimental study of natural processes

A.L. Perchuk a, b , V.O. Yapaskurt c , V.V. Davydova c
a Institute of Geology of Ore Deposits, Petrography, Mineralogy, and Geochemistry, Russian Academy of Sciences,
35 Staromonetnyi per., Moscow, 119017, Russia
b Institute of Experimental Mineralogy, Chernogolovka, 142432, Russia
c Lomonosov Moscow State University, Geological Department, Vorob'evy Gory, Moscow, 119899, Russia
Keywords: Eclogite; melting; garnet; inclusions
Pages: 310-312

Abstract >>
Experiment with poikilitic garnet at 3 GPa and 800

Equilibria in the system Au-Ag-S-fluid: computed and experimental data

Yu.V. Laptev
United Institute of Geology, Geophysics and Mineralogy, Siberian Branch of the RAS, 3 prosp. Akad. Koptyuga, Novosibirsk, 630090, Russia
Keywords: Thermodynamic computations; metastable equilibrium; gold; electrum; silver; pyrite ore deposits; hydrothermal processes
Pages: 313-322

Abstract >>
We present results of computations on the interaction of solid-phase electrum-argentite-pyrite (weight ratios 2·10-5 / 2 · 10-3 /1 and 2·10-5 / 4·10-2 / 1>) association with Cl-containing aqueous moderately acid solutions (0.5m NaCl, pH = 3.08) at 300

Mesozoic and Cenozoic collisional structures of the southern Great Altai

B.M. Chikov, S.V. Zinoviev, E.V. Deyev
Institute of Geology and Mineralogy, Siberian Branch of the Russian Academy of Sciences, 3 prosp. Akad. Koptyuga, Novosibirsk, 630090, Russia
Keywords: Continental collision; Mesozoic-Cenozoic tectonic events; dynamic metamorphism; Great Altai; Central Asia
Pages: 323-331

Abstract >>
We suggest a model of the continental collisional framework of the southern Great Altai (Central Asia) produced by the convergence of the Tuva-Mongolia and Jonggaria terranes (microplates) during the latest Permian-Mesozoic and Cenozoic tectonic activity. The collisional structures in the region classified on the basis of their geometry and deformation style, dynamic metamorphism, and compositions of tectonites are of three main types: (i) mosaic terranes made up of large weakly deformed Paleozoic blocks separated by younger shear zones, (ii) collisional deformation systems involving post-Paleozoic structures, parallel faults oriented along collisional deformation systems, and relict lenses of Paleozoic orogenic complexes, and (iii) isolated zones of dynamic metamorphism composed mostly of collisional tectonites.

Morphostructures and Cenozoic deposits on the right bank of the Kizir River (East Sayan)

N.N. Popova a , A.V. Matsera b
a Krasnoyarskgeols'emka Enterprise, 3d ul. Berezina, Krasnoyark, 660020, Russia
b Russian State Oil and Gas University, 65 Leninskii prosp., Moscow, 199991, Russia
Keywords: Morphostructures; buried placers; Cenozoic; East Sayan
Pages: 332-336

Abstract >>
Study of morphostructures and Cenozoic deposits is important for reconstructing the history of the recent evolution of East Sayan and search for buried gold placers. Regional positive morphostructures of mountains with well-pronounced relief stages have been recognized in the Altai-Sayan area. The upper stage is referred to the Cretaceous-Paleogene; the middle one, to the Miocene-Pliocene; and the lower stage is dated at the Late Pliocene-Early Pleistocene. Negative morphostructures are recognized as a chain of intramontane basins and graben-like valleys of the Transbaikalian type. Troughs in the section bottom are filled with Cretaceous-Paleogene clayey crusts of weathering overlain by Neogene-Pleistocene deposits of complex composition. We studied the sections of Cenozoic deposits in the valleys of the Shinda and Verkhnyaya Chinzheba Rivers and made their palynological description.

Array magnetotelluric soundings in the active seismic area of Northern Tien Shan

A.K. Rybina, V.V. Spichak b , V.Yu. Batalev a , E.A. Bataleva a , V.E. Matyukov a
a Research Station, Russian Academy of Sciences, Bishkek, 720049, Kyrgyzstan
b Geoelectromagnetic Research Center, Shmidt Institute of Physics of the Earth, Russian Academy of Sciences, P.O. Box 30, Troitsk,
Moscow Region, 142190, Russia
Keywords: Crust; faults; thrust; MT soundings; electrical conductivity structure; impedance tensor; Tien Shan
Pages: 337-349

Abstract >>
High-density array MT soundings of the crust in the seismically active northern Tien Shan were performed using Phoenix MTU-5 stations in the Bishkek Geodynamic Polygon, at the junction of the Chu basin and the Kyrgyz Range. The MT transfer functions were determined to an accuracy of 1-2% (amplitude) and about 0.5-0.8 deg (phase) in most of 145 soundings. Preliminary analysis of the collected data aimed at estimating the geoelectrical dimensionality. The Bahr decomposition analysis indicated the presence of local 3D structures in the crust of the area superposed on the regional 2D structure.

Time-dependent stress change during failure of rocks

V.T. Belikov, A.F. Shestakov
Institute of Geophysics, Ural Branch of the RAS 100, ul. Amundsena, Ekaterinburg, 620016, Russia
Keywords: Rock failure; energy balance; surface energy; stress; fracture-related stress change
Pages: 350-359

Abstract >>
The energy balance of a solid subject to fracture has been explored using heat and mass transfer equations with regard to the volumetric and superficial components. In the suggested model, brittle fracture of a cracked solid considered as a heterogeneous two-phase medium is described by an equation analogous to the Griffith's criterion for propagation of a single crack. The derived equation is used, together with estimates of relative change in specific interface area, to study the respective change of free strain energy and pressure in rocks associated with failure.