Volume 28, 2, 2009 |
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L.A. Maslov, V.M. Anokhin. Principles of directivity of lineaments and faults at the bottom of the Sea of Japan Russian part 3 S.P. Pletnev. Paleodepths of the Sea of Okhotsk sedimentary basin in the Cenozoic 17 V.L. Bezverkhny, Ye.B. Osipova. A possible mechanism of inversion of lithosphere vertical movements within back-arc basins of the West Pacific region 27 M.A. Mishkin, G.M. Vovna. The origin of the deep metamorphic complexes of the Early Proterozoic fold framing, eastern part of the Aldan shield 36 A.N. Filippov, I.V. Kemkin. Siliceous volcanogenic assemblages of the western Sikhote-Alin: stratigraphy and origin 53 L.F. Mishin. Eutectoid and cotectoid petrographic types of acid volcanic and subvolcanic rocks of the marginal-continental volcanic belts, as exemplified by eastern Asia 69 V.B. Kaplun. The geoelectrical section of the lithosphere in the central part of the Middle Amur sedimentary basin from magnetotelluric sounding data (Far East) 86 N.I. Belyanina, P.S. Belyanin, Ye.V. Mituryova. New evidence of the Razdolnaya River flow reorientation in the Pleistocene, Southern Primorye 99 A.I. Gresov, A.I. Obzhirov, Ye.V. Korovitskaya, R.B. Shakirov. Methane content and prospects of development of methane resources of the coal basins and deposits of the southern Far East 103 L.A. Maslov, V.M. Anokhin Principles of directivity of lineaments and faults at the bottom of the Sea of Japan Russian part The configuration of the lineament-disjunctive network of the Sea of Japan Russian part was studied on the sheets K-52 and K-53 using geophysical and geomorphological data. Structural zoning of this water area bottom was performed. Azimuths of the lineament and fault strike were measured. Roses of lineament and fault directivity for certain areas of the sea bottom and for the whole region were constructed. Principles of directivity of lineaments and faults were shown. A comparison was made between the linear structures directivity of the Sea of Japan Russian part and the general directivity of the main systems of the global disjunctive network. The following conclusions were made. 1. A single lineament-disjunctive network with four principal systems of directions exists in the region: submeridional (0–5°), sublateral (86–90°), NE-diagonal (36–65°), and SE-diagonal (136–140°); 2. Conformity of the directions of these four principal systems with the directions of four main systems of the global disjunctive network (planetary fracturing); 3. The essentially rotational genesis of the identified network; 4. The patterns of distribution and orientation of faults and lineaments are determined by two interacting factors: stress and deformation concentration in the areas of the gradient of bed thickness, and variations of the rate of rotation of the Earth (the first factor determines the place of the fault origin; the second, its orientation). S.P. Pletnev Paleodepths of the Sea of Okhotsk sedimentary basin in the Cenozoic The biofacial analysis of fauna of benthic foraminifera in the deposits of the Sea of Okhotsk paleobasin has shown the presence in it of typical abyssal dwellers in Oligocene-Miocene time and their absence in the Pliocene and Pleistocene. The penetration and existence of such fauna in the Sea of Okhotsk basin was conditioned by the presence of deep-sea basins (> 2000m) there and active water exchange with the Pacific Ocean. The Sakhalin phase of folding at the Neogene-Quaternary boundary initiated upheaval of the Japanese-Kuril cordillera and separation of deep-sea basins of the seas of Japan and Okhotsk from the ocean. This fact caused unfavorable conditions for migration and existence of Pacific abyssal fauna. The similarity and common tendencies in the development of Neogene fauna of the seas of Japan and Okhotsk benthic foraminifera indicate the absence of such narrow and shallow-marine thresholds as the present-day Nevelskoy, and Sangarsky straits. Such bottom topography favored intensive water exchange from south to north, which actually determined the features of similarity in the composition of benthic foraminifera of the seas of Japan and Okhotsk paleobasins. V.L. Bezverkhny, Ye.B. Osipova A possible mechanism of inversion of lithosphere vertical movements within back-arc basins of the West Pacific region There have been presented the results of the study of the three-layer tectonosphere model for the West Pacific transition zone based on the modelling of the inhomogeneous medium movements caused by the asthenosphere local density reduction. The asthenosphere is characterized by viscosity reducing due to concentration of fluids. We used the viscous liquid movement equation in the Stokes approximation. There has been shown that the back-arc anomalous asthenosphere can move as a convective cell with the uprising flow in the zone of its maximal density reduction and distinct lithosphere extension over it. At the initial stages this process results in the formation of the crustal uplift, which is transformed into the downwarp system as the asthenosphere viscosity decreases to the values of about 4.0.1019 Pas. and less. The modelling results agree satisfactorily with reconstructions of Cretaceous-Cenozoic structure-and substance evolution in the Sea of Okhotsk region. M.A. Mishkin, G.M. Vovna The origin of the deep metamorphic complexes of the Early Proterozoic fold framing, eastern part of the Aldan shield It is shown that the base of the geologic section of the deep Early Proterozoic Dzhugdzhur and Sunnagin complexes is made up of the metabasite-enderbitic association. According to the patterns of distribution of the main rock-forming elements and trace elements, volcanics of the calc-alkaline and komatiite-tholeiitic series are the dominant protoliths of the association rocks. The accepted model of formation of the initial volcanics includes two stages. The first stage provides decompressional partial melting of the substance of the ascending mantle plume attended by the formation of melts of the komatiite-tholeiitic association. The second stage involves the formation of volcanics of the calc-alkaline series by partial melting of the initial metabasite crust due to the heat of the ascending mantle plume. The formation of the protoliths of the metabasite-enderbitic association occurred in the Early Proterozoic. A.N. Filippov, I.V. Kemkin Siliceous volcanogenic assemblages of the western Sikhote-Alin: stratigraphy and origin New data are offered on the age and structure of the siliceous volcanogenic assemblages from the lower reaches of the Ussuri River. These assemblages, which earlier were rated as part of one stratigraphic unit, are divided into the Snarsky tectonostratigraphic complex (end of the Middle Jurassic – Middle Aptian) and a basalt rock series (presumably, Campanian-Maastrichian). The Snarsky complex is made up of basic volcanics, cherts, cherty-clay rocks, and a small amount of limestone, sandstone and conglomerate. It is distinguished by a large quantity of basalts of different origin, abundance of volcanomictic and pyroclastic material in the cherty-clay rocks, absence of fragmental rocks of the continental convergence zone, and facial heterogeneity of the deposits. The complex is considered as the south-eastern continuation of the Kiselevka-Manoma terrane. Its origin is presumed to be related to tectonic piling up of genetically heterogeneous assemblages. Basalts, andesite basalts, their tuffs, and tuff conglomerates are assigned to the basalt rock series. Granites and garnet-bearing acid effusives are abundant among the fragments in the tuff conglomerates. The rock series formed in the late Cretaceous on the paleocontinent’s crystalline basement. L.F. Mishin Eutectoid and cotectoid petrographic types of acid volcanic and subvolcanic rocks of the marginal-continental volcanic belts, as exemplified by eastern Asia As exemplified by the marginal-continental volcanic belts of eastern Asia, the petrography and geochemistry of volcanic and subvolcanic rocks of acid composition are investigated. The cotectoid and the eutectoid type are distinguished among them. The eutectoid type is characterized by its nonequilibrium mineralogical composition, which includes an early “gabbro” paragenesis of impregnations (pyroxene, basic plagioclase, occasional olivine and amphibole), “granite” paragenesis of impregnations (soda-potash feldspar, quartz, and biotite), and the bulk of the composition represented by dry quartz-feldspathic eutectics. A linear dependence is noted between the quantity of impregnations of gabbro paragenesis and SiO2. The whole petrochemical variety of the eutectoid type rocks is determined by the quantitative ratio of gabbro paragenesis impregnations to the bulk of the composition. The cotectoid rocks are dominated by rare-impregnation and aphyric differences; melanocratic inclusions and xenogenic minerals are absent in them. In the cotectoid-type rocks the compositions of impregnations and of the bulk are complementary with respect to the bulk composition of the rocks and give evidence of equilibrium cotectic crystallization. V.B. Kaplun The geoelectrical section of the lithosphere in the central part of the Middle Amur sedimentary basin from magnetotelluric sounding data (Far East) The results of magnetotelluric sounding along the profile running across strike of the Middle Amur sedimentary basin are considered. An analysis was done of the field work results, and different factors are examined which govern the behavior of the sounding curves. Based on the results of previous work done by the magnetotelluric sounding method, a reference curve and a reference geoelectrical section were indicated within the basin, which made it possible to compensate the influence of different geoelectrical inhomogeneities and construct a start model for bivariate mathematical modeling based on the field data. The investigations resulted in the construction of the geoelectrical model of the lithosphere structure of the Middle Amur sedimentary basin across its strike. N.I. Belyanina, P.S. Belyanin New data on the pollen stratigraphy of the Late Neopleistocene-Holocene, eastern sector of the Circum-Khanka plain Problems of the dynamics of vegetation development of the Late Neopleistocene – Holocene of the eastern sector of the Khanka Lake plain are discussed. In the spore-and-pollen spectra of deposits penetrated by holes in the eastern sector of the Lake Khanka water area, phases of paleovegetation development are identified. The landscapes of the Riss-Würmian Interglacial (Q1III) were characterized by vegetation communities of oak – broad-leaved forests in the presence of hornbeam, beech, pine and tsuga. In Würmian-2 time (Q3III), southern Boreal dark-coniferous taiga was widespread. The glacial period of Sartan time (Q4III) was dominated by formations of northern Boreal taiga vegetation with alder forests, and maries. The Holocene Optimum (Q2III) is characterized by the development of elm-oak forests with hornbeam. A.I. Gresov, A.I. Obzhirov, Ye.V. Korovitskaya, R.B. Shakirov Methane content and prospects of development of methane resources of the coal basins and deposits of the southern Far East The paper offers a short description of methane content of coal basins and deposits of the southern Far East. Values of methane content of coal beds with respect to their depth of occurrence are given, which make it possible to carry out forecast of methane resources in the area of poor geologic and gas knowledge and in the areas lacking relevant methane content investigation.. Two groups of coal-methane deposits are distinguished, which are characterized by different features of methane content and methane resources distribution. These features are conditioned by a number of gas controlling factors. The principal ideas of the geo-technological concept of assessment of coal methane resources and prospects of their extraction are formulated. Three groups of deposits are distinguished with respect to the prospects of commercial development of methane resources of different categories implying their extraction potential. The information database of methane resources of coal beds of the basins and deposits of the southern Far East is given. The estimation of prospects of the organization of coal-methane mining in the southern Far East is made. |