Òîì 32, 3, 2013 |
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V.B. Kaplun. Geoelectrical section of the
lithosphere of the southern Amur-Zeya sedimentary basin from results of
magnetotelluric soundings 3 V.P. Utkin. Strike-slip-related structural paragenesis and its role in continental riftogenesis of the eastern margin of Asia 21 I.V. Buchko, A.A. Sorokin, N.M. Kudryashov. Late Paleozoic gabbroids of Lesser Khingan terrane (eastern Central Asian fold belt): age, geochemistry, and tectonic position 44 N.G. Razzhigaeva, L.A. Ganzey, N.I. Belyanina, T.A. Grabennikova, Kh.A. Arslanov, N.F. Pshenichnikova, A.V. Rybin. Role of climatic and volcanogenic factors in the formation of organogenic deposits and landscape evolution of the Simushir Island, Central Kurils, during theMiddle/Late Holocene 55 A.V. Grebennikov, V.K. Popov, A.I. Khanchuk. Experienceof petrochemical typification of acid volcanic rocks from different geodynamic settings 68 S.V. Zyabrev, V.I. Ano'kin. New data on the ages of deposits in the Kiselevka-Manoma accretionary complex based on radiolarian fossils 74 V.D. Kozlov, S.V. Efremov. Mantle sources of granitoids of Central Chukotka (Iultin W-Sn ore district) 84 A.N. Fomin, G.L. Kirillova, E.A. Kostyreva, V.N. Melenevsky, G.A. Zlobin. Late Jurassic-Early Cretaceous terrigenous complex of the North Sikhote-Alin: composition, structure, geochemistry of the organic matter 93 D.A. Safonov, A.V. Konovalov. FOCMEC Computer Program Testing For Earthquake Source Mechanism Determination, Kuril-Okhotsk and Sakhalin Region 102 Ye.G. Glushkova, Z.S. Nikiforova. On the placer gold original sources of the Urinsky anticlinorium (south- eastern Siberian platform) 118 V.B. Kaplun Geoelectrical section of the lithosphere of the southern Amur-Zeya sedimentary basin from results of magnetotelluric soundings Magnetotelluric soundings are carried out in the Amur-Zeya sedimentary basin along 200 km long profile KorfovoAstashikha-Novosergeevka. The profile is located in the southern part of the basin and does not overcome its borders. The audiomagnetotelluric (AMT) soundings were conducted in the profile section KorfovoAstashikha at 1-km spaced observation sites, whereas in the section Korfovo-Novosergeevka combined AMT+MTS soundings were carried out at 5-km spaced observation sites. The magnetotelluric analysis of the data, characterizing the section, has been performed including MTS curve shapes and their variation along the profile, the shape of the main and additional impedance polar diagrams, the inhomogeneity parameter N values and those of asymmetry parameter, or skewness values. The dimensions of the geological medium have been estimated and the methods of magnetotelluric data interpretation have been chosen. The geoelectrical sections have been constructed down to 3 km and 150 km depths. The sedimentary cover and the crustal and upper mantle structures have been studied and their electrical properties have been determined. The thickness of the sedimentary cover reaches 1.51.7 km in the grabens of the basin. The blocks with different resistivity values were defined in the basement. The crustal thickness attaining to 3840 km was revealed from a contrasting alternation of electrical resistivity values. This crustal thickness value is consistent with that derived from seismic data. The geoelectrical section of the upper mantle of the basin has a relatively simple structure. A high resistivity layer with the values from the first hundreds to one thousand Ohm m was detected at a 5080 km depth range against the background of low electrical resistivity values of 2030 Ohm m observed within the mantle. This layer is not continuous but is divided into blocks by the low resistivity zones penetrating into the middle crust. These zones correspond to differently originated faults. The prospects of oil and gas content have been estimated for separate grabens of the basin. Key words: magnetotelluric soundings, deep structure, lithosphere, Amur-Zeya sedimentary basin, Far East. V.P. Utkin Strike-slip-related structural paragenesis and its role in continental riftogenesis of the eastern margin of Asia Spatial-genetic correlations of the transit fault systems belonging to the Eastern Asian Global Strike-Slip Fault Zone (EAGSSFZ) are analyzed. It is established that from the Okhotsk Sea to the South China Sea the EAGSSFZ infrastructure is identical to internal structure of world-known natural and experimental strike-slip fault zones. This corroborates evolution of the EAGSSFZ as an integral structure. Structural-kinematic analysis covers such systems as the Tan-Lu-Sikhote-Alin (TS) system of the NNE-trending (25-30o) sinistral faults and the Bohai-Amur (BA) system of the NE-trending (50-70o) reverse-and-strike-slip faults. The systems are shown to form as structural paragenesis for 2 main stages. The first Jurassic-to-Early-Cretaceous (strike-slip-and-thrust) stage took place under the NNW general compression with formation of the TS system of sinistral faults and their structural paragenesis (compression structures) as upthrust-and-thrusts of the BA-system. The second Late-Cretaceous-to-Cenozoic (strike-slip-and-pull-apart) stage occurred under the SW tangential compression. The latter resulted from left-lateral displacement of the continental crust in the SW direction along the Central Sikhote-Alin deep fault. Under the created dynamic conditions upthrust-and-thrust kinematics of the BA-system changed into sinistral one. Strike-slip faults formed under transtension regime (strike-slip with tension) that caused the development of the pull-apart structures in which a left-lateral component of tension played a key role. Synchronously, the Tan-Lu strike-slip fault was pulled into tension with formation of a rift valley and discrete development of sedimentary basins along the fault. Key words: strike-slip faults, structural paragenesis, dynamics of structure formation, structural-dynamic stages, sedimentary basins, riftogenesis, Far East. I.V. Buchko, A.A. Sorokin, N.M. Kudryashov Late Paleozoic gabbroids of the Lesser Khingan terrane (eastern Central Asian fold belt): age, geochemistry, and tectonic position The papers considers the results of mineralogical, geochemical, and geochronological studies of the leucogabbroids of the Karagai massif located in the vicinity of the Lesser Khingan superterrane, Central Asian fold belt. The main features of rock-forming gabbroid minerals are high calcium content of clinopyroxene, corresponding in composition to diopside-sahlite (Wo48-51En33-39Fs11-16) or augite (Wo22-35En46-47Fs18-33), high basicity of plagioclase (An90-92), and the presence of primarily magmatic magnesium amphibole. The age of the massif is 257±1 Ma as established by U-Pb zircon dating. The matter composition of gabbroids evidences that they were most probably formed in the island arc or active continental margin geodynamic settings. Taken into account existing geodynamic reconstructions and data obtained within the framework of the present study, it should be suggested that the formation of Late Paleozoic gabbroids of the Karagay massif is related with the final stages of subduction processes which preceded terrane accretion of the eastern part of the Central Asian fold belt. Key words: gabbro, Late Paleozoic, geodynamics, Lesser Khingan terrane, Central Asian fold belt. N.G. Razzhigaeva, L.A. Ganzey, N.I. Belyanina, T.A. Grabennikova, Kh.A. Arslanov, N.F. Pshenichnikova, A.V. Rybin Role of climatic and volcanogenic factors in the formation of organogenic deposits and landscape evolution of the Simushir Island, Central Kurils, during theMiddle/Late Holocene Landscape evolution stages of the Simushir Island in the Middle/Late Holocene are distinguished, boundaries of their reconstruction are defined, and the role of the climatic changes and volcanic eruptions in the development of natural components are clarified. Paleoreconstructions are based on the investigation of stratigarphic sections of soil-pyroclastic covers in different parts of the island. Besides, the section of the peat swamp on the coast of the Dushny Bay has been studied. Spores and pollen analysis of the buried, recent soils and peat swamp has been performed, and the diatom flora was examined. An age correlation of the events was made on the basis of radiocarbon dating and tephrostratigraphic data. Key words: Holocene, climatic changes, volcanic eruptions, paleolandscapes, Central Kurils. A.V. Grebennikov, V.K. Popov, A.I. Khanchuk
Experienceof petrochemical typification of acid volcanic rocks from different geodynamic settings The paper presents the results of empiric construction of classification diagram for acid volcanic rocks from different geodynamic settings which reflect the specific features of their chemical composition. Testing of the binary diagram Al2O3/(CaO+MgO) – Fe2O3Tot/(CaO+MgO) by the example of composition of the Late Cretaceous (Primorsky, Siyanovsky, Kamensky and Levosobolevsky ) and Paleogene (Bogopolsky) volcanic complexes of East Sikhote-Alin shows that it can be used to determine tectonic settings of acid volcanism manifestation during ancient geological periods. Key words: geochemical classification, geodynamic settings, petrogenic elements, rhyolites. S.V. Zyabrev, V.I. Ano'kin
New data on the ages of deposits in the Kiselevka-Manoma accretionary complex based on radiolarian fossils The Kiselevka-Manoma accretionary complex is the youngest in the Russian Far East region, and is composed of Jurassic to Lower Cretaceous pelagic and hemipelagic oceanic deposits. Radiolarian biostratigraphic study clarified the stratigraphy of the upper portion of the complex in the vicinity of Kiselevka village in the Lower Amur region. Transition from pelagic to hemipelagic sedimentation occurs in the geochronological interval from the late Barremian through to middle Aptian in different parts of the complex. The age of the accretion of the oceanic materials is defined as post-middle Aptian. Key words: biostratigraphy, Radiolaria, Jurassic, Cretaceous, oceanic deposits, Kiselevka-Manoma accretionary complex, Russian Far East. V.D. Kozlov, S.V. Efremov Mantle sources of granitoids of Central Chukotka (Iultin w-sn ore district) The petrochemical and rare-element composition of all magmatic rocks of the Iultin region (from early lamprophyres and monzodiorites to late rare-metal ore-bearing leucogranites) has been studied. The differential normalizing of the obtained data from clarkes of the analytical data of the gabbroids “ diorites–granodiorites–granites demonstrates the primary maximum enrichment of the monzonitoids and lamprophyres by volatile F and B and granitophyle rare elements (Li, Rb, Cs, Be, Sn, W, Mo, Pb). This confirms the endogenic (mantle) source of the high incoherent rare element ñoncentrations in the granitoids of the region. The primary enrichment of the deep-seated granitoids by the volatile and incoherent rare elements was the major factor of subsequent redistribution and concentration of rare elements during the magmatic differentiation process and forming of the ultra-rare-metal leucogranitic intrusions. Key words: petrochemistry, rare-element composition, lamprophyres, monzodiorites, granodiorites, leucogranites, Central Chukotka. A.N. Fomin, G.L. Kirillova, E.A. Kostyreva, V.N. Melenevsky, G.A. Zlobin Fractured reservoirs and hydrocarbon potential of the Late Jurassic-Early Cretaceous terrigenous complex of the North Sikhote-Alin The papers considers the composition and structure of the Late Jurassic to Early Cretaceous terrigenous complex located in the northern Sikhote-Alin in the marginal part of which in 2008 cutting-through of the Kuznetsovsky tunnel began. In the course of the works new outcrops in the road cavities appeared. Boreholes up to 300 m deep were drilled above the tunnel top being investigated and tested by the authors in 2010. To estimate oil and gas potential prospects of this complex, rock fracturing and organic matter have been examined. The studies included the determination of maceral reflectance, organic carbon content, pyrolithic characteristics (Tmax, S1, S2), chloroform bitumoids, and their group and hydrocarbon composition. The carried out investigations are obvious insufficient to evaluate oil and gas prospects of the Late Jurassic to Early Cretaceous Sikhote-Alin complex, but there is no question that the obtained results could be useful for future investigations of the region. Key words: composition, structure, geochemistry, organic matter, terrigenous complex, Jurassic, Cretaceous, Sikhote-Alin, Far East. D.A. Safonov, A.V. Konovalov FOCMEC computer program testing for determination of earthquake source mechanism, the Kuril-Okhotsk and Sakhalin Regions The results of FOCMEC computer program testing for single and mass determination of earthquake source mechanisms in the Kuril-Okhotsk and the Sakhalin regions were considered. Mass determination of source mechanism of earthquakes, occurred in the Kuril-Okhotsk region in 2005-2009, was carried out. Accuracy of the calculations was estimated by comparing the determined mechanisms with the solutions of world and regional seismological agencies. The paper presents the results of earthquake source mechanism determination, considering some seismic events in Sakhalin Island, local tectonic settings and its interpretation, and suggests methodological recommendations. Key words: earthquake, source mechanism, seismic station, digital recordings, seismic dislocation parameters, Sakhalin region. Ye.G. Glushkova, Z.S. Nikiforova On the placer gold original sources of the Urinsky anticlinorium (southeastern Siberian platform) Based on the study of the mineralogical and geochemical features of placer gold of the Urinsky anticlinorium, available published and fund materials, along with the history of its geological evolution, the original sources of low-sulfide mineralization of gold-quartz and hypabyssal gold-sulfide-quartz formations of the Mesozoic age, including those of the Kuranakh type have been first proposed . Keys words: typomorphism, mineralogical-geochemical features, placer gold, mineralization, formation, Urinsky anticlinorium. |