Volume 28, 4, 2009 |
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O.V. Avchenko, I.A. Alexandrov, V.O. Khudolozhkin, M.A. Mishkin. Fluid regime of amphibolite facies metamorphism of the Dzhugdzhur-Stanovoy fold belt (Far East) 3 Koloskov A.V., Flerov G.B., Kovalenko D.V. Late Cretaceous–Paleocene magmatic complexes of Central Kamchatka: geologic position and features of matter composition 16 N.P. Romanovsky, Yu. F. Malyshev, M.V. Goroshko, V.G.Gurovich, M.I. Kopylov. Mesozoic granitoid magmatism and metallogeny of the Central Asian and Pacific belts junction area 35 A.N. Ovsyuchenko, S.V. Trofimenko, A.V. Marakhanov, P.S. Karasev, Ye.A. Rogozhin, V.S. Imaev, V.M. Nikitin, N.N. Grib. Detailed geologic and geophysical investigations of zones of active faults, and seismic hazard of the South Yakutia region 55 I.S. Brandt, S.V. Rasskazov, V.K. Popov, S.B. Brandt. Potassic specificity of the Sineutesovskaya depression basalts: Geochemical correlations and problems of K-Ar dating (Southern Primorye) 75 S.Ye. Aprelkov, S.V. Popruzhenko. Penzhina-West Kamchaka fold zone and Ukelayat-Sredinnyi block in the structure of the Koryak upland and Kamchatka 90 M.E. Melnikov, S.P. Pletnev, I.A. Basov, T.E. Sedysheva. New data on the morphology and geologic structure of the Gramberg Guyot (Magellan Seamounts, Pacific Ocean) 105 B.S. Arkhipov. Chemical composition and metal content of thermal waters of the north-eastern Sikhote-Alin (Far East) 116 Discussions S.Î. Maksimov . “Eutectoid and cotectoid” types of volcanic rocks 123 Anniversaries Boris I. Vasil'ev (to the 80-th anniversary) 128 O.V. Avchenko, I.A. Alexandrov, V.O. Khudolozhkin, M.A. Mishkin Fluid regime of amphibolite-facies metamorphism of the Dzhugdzhur-Stanovoy fold area (Far East A consistent model has been constructed for fluid-rock interaction during amphibolite-facies metamorphism of the Dzhugdzhur-Stanovoy fold area. The model is based on gas chromatographic and electrochemical measurements, computer simulation of natural assemblages, and evaluation of the muscovite+quartz stability field. The model allows fluid differentiation into the “internal” and the “external” fluid, where the “internal” fluid is composed of volatile phases of the rock itself, while the “external” fluid arrives from the outer source – mantle or other reservoir. It is established that gas chromatographic and electrochemical measurements refer to the “external” fluid, whereas the redox state of the rock estimated from mineral equilibria is related to the “internal” fluid; the latter’s composition being buffered by minerals involved in the equilibria. Incidentally, the “external” fluid trapped by the rock maintains its own redox state only at the retrograde stage of the metamorphic event, when reactions involving solid phases are slackened drastically, and the buffer strength of the mineral associations is minimized. This aspect explains the contradiction between wide variations of oxidation of the mineral equilibria (lgfO2 -15 to -20) on the one hand, and the constancy of oxidation of the “external” fluid according to gas chromatographic and electrochemical measurements, on the other hand. The main reason for the prevalence of amphibole-bearing assemblages in the Dzhugdzhur-Stanovoy fold area is the high H2O pressure in the “external” metamorphic fluid. The composition of the “external” fluid is characterized by the following conditions: PH2Î>=0.7PS and ÐÑÎ2/PH2O = 0.01–0.3. The oxidation potential of the “external” fluid is close to that of the H2O-C model system (water vapor saturated with carbon). V.A. Koloskov, G.B. Flerov, D.V. Kovalenko Late Cretaceous – Paleocene magmatic complexes of Central Kamchatka: geologic position and features of matter composition A comparative analysis was made of the data on Late Cretaceous-Paleocene volcanism of four areas of Kamchatka: Prav. Tolbachik – Lev. Shchapina – Adrianovka rivers interfluve (northern Tumrok Ridge), the area south of the Ipuin River - Mt Hrebtovaya (northern Valaginsky Ridge), the area of Mt Savulch (Kitilgina River upper reaches, northern Valaginsky Ridge), and: Kirganik – Lev. Kolpakova rivers interfluve (Sredinnyy Ridge). New data on petrochemical, geochemical and isotopic composition of volcanic rocks from these areas are offered. The analysis of these materials together with the already published data on volcanics and also on plutonic rocks of close composition and age made it possible to establish the following: 1) the basaltoids under study are referred to the trachyandesite series with transition to the maymechite-picrite rock association, 2) in the rocks of the Valaginsky - Tumrok – Sredinnyy ridges alkali content increases with simultaneous increase in Rb concentration; the contents of highly charged and radioactive elements first drop and then grow. In the coordinates Ybn-Cen the presence of two trends is established: positive, which embraces the majority of volcanic and plutonic rocks; and negative, peculiar to the maymechite-picrite association. The former trend reflects rock evolution during crystallization differentiation; and the latter, a different degree of melting of initial substrate. Possible reconstructions of geodynamic conditions of volcanism manifestation are discussed. N.P. Romanovsky, Yu. F. Malyshev, M.V.Goroshko, V.G.Gurovich, M.I. Kopylov Mesozoic granitoid magmatism and metallogeny of the Central Asian and Pacific belts junction area Data on Mesozoic granitoids of the Central Asian and Pacific belts junction area and the adjacent platforms is summarized. Maps of massifs, extensiveness of granitoid magmatism, Mesozoic plumes manifestation and relief of the asthenosphere surface have been compiled. Location of major ore deposits are plotted on the maps. The distribution chart has been constructed for these deposits in the coordinates of the crust and lithosphere. Estimation of the depth of occurrence of the sources of large and superlarge gold, tin, polymetal, molybdenum, tungsten and uranium deposits has been made. Areas promising for major deposits are defined. A.N. Ovsyuchenko, S.V. Trofimenko, A.V. Marakhanov, P.S. Karasev, Ye.A. Rogozhin, V.S. Imaev, V.M. Nikitin, N.N. Grib Detailed geologic and geophysical investigations of zones of active faults, and seismic hazard of the South Yakutia region Active faults play a key role in morphostructure formation and seismic control within the Olekma-Stanovoy seismic zone. Detailed geologic-structural and morphotectonic investigations carried out in the fault zones made it possible to assess kinematics of active faults and the degree of their activity in the Holocene (the last 10,000 years). Ancient faults are present among them, for example, the Stanovoy suture of Proterozoic age. Most faults are young – Late Mesozoic and Cenozoic. The investigations were paleoseismogeologically oriented and were accompanied with mine workings driving through the land forms, which can be associated with zones of active tectonic dislocations; the latter have been geophysically prestudied. The practised approach made it possible to substantially specify the available data on the seismotectonics and potential seismic hazard of the region. I.S. Brandt, S.V. Rasskazov, V.K. Popov, S.B. Brandt Potassic specificity of basalts of the Sineutesovskaya depression: geochemical correlations and problems of K-Ar dating (Southern Primorye) New data are offered on the structure of the sections, chemical composition and age of volcanogenic-sedimentary and effusive assemblages of the Sineutesovskaya depression (Southern Primorye). The rocks filling the Sineutesovskaya depression are represented by two packets: the lower one made up of sedimentary-volcanogenic coal-bearing rocks – a stratotype of the Sineutesovskaya Formation, and the upper packet composed of tephroidal deposits and overlying basalt flows. The R-Ar dating 22.0 ± 1.0 Ma was obtained for the very tops of basalt flow. The middle and the lower part of the lava packet shows dating rejuvenation. The distortion of the datings is attributed to basalt heating as a result of Sineutesovskaya brown coals (underlying the volcanic cover) inflammation. Calculations show that argon could only partially be removed from the basalts at the expense of conductive heat transfer and was lost mainly due to hot gases infiltration in an inhomogeneous fractured medium. Basalt volcanism in the continental margin of Southern Primorye and adjacent territories of Korea and China which was evident at the Oligocene-Miocene boundary and preceded Early-Middle Miocene spreading and formation of the Sea of Japan depression. The origin of spreading of the Sea of Japan depression is indicated by non-differentiated moderately alkaline basalts of the intraplate geochemical type which became apparent within the Ambinskaya depression and a number of other structures of Southern Primorye, and also by intraplate alkaline basalts of the P’ohang graben, Korean Peninsula. Potassium-trachybasalt volcanism was locally evident within riftogenic depressions and shield volcanoes. In some structures it terminated in intermediate and acid volcanism. Such evolution of volcanism is related to selective contamination of basalt melts in their interaction with crustal acid material, and to generation of acid anatectic meltings. S.Ye. Aprelkov, S.V. Popruzhenko Penzhina-West Kamchaka fold zone and Ukelayat-Sredinnyi block in the structure of the Koryak upland and Kamchatka A tectonic map of the referred region, whose principal tectonic elements are areas with the consolidated Earth’s crust and zones with a fold imbricated-overthrust structure, was compiled on the basis of geologic and geophysical research. The relationship between the fold zone and the crustal blocks, and paleogeodynamic conditions of their formation are considered. M.Ye. Melnikov, S.P. Pletnev, I.A. Basov, T.Ye. Sedysheva New data on the morphology and geologic structure of the Gramberg Guyot (Magellan Seamounts, Pacific Ocean) Expedition investigations carried out by the “Yuzhmorgeologiya” Scientific Center in 2002–2004 in the western Pacific Ocean on board R/V “Gelendzhik” resulted in new material, which made it possible to define the features of the morphological structure of the Gramberg Guyot and specify the matter and paleontological character of the structural formation complexes of rocks from Early Cretaceous through Pleistocene. The analysis of macro- and microfauna in sedimentary rocks allowed us to distinguish the “transgressive” phases in the development of the Guyot: Cenomanian-Turonian, Late Campanian-Maastrichtian, and Late Cenozoic. Sedimentation conditions of the Gramberg Guyot are analyzed as compared with other guyots of the Magellan Seamounts. B.S. Arkhipov Chemical composition and metal content of thermal waters of the north-eastern Sikhote-Alin (Far East) A pattern of distribution of alkaline nitrogen hydrotherms of the north-eastern Sikhote-Alin is offered. A comparative characteristic of gas, chemical and microcomponent composition of thermal waters from the Lazarevskaya springs (Tumninskiy and Annenskiy deposits) is given. The reasons for the change in the chemical composition of hydrotherms at exploitation sites are analyzed. |