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Russian Geology and Geophysics

2007 year, number 11

1.
Structure of bottom sediments in Lake Hцvsgцl: geological and climate controls

Hцvsgцl Drilling Project Group: A.A. Abzaevaa, E.V. Bezrukova a , V.A. Bychinsky a , S.A. Fedenyad, V.F. Geletiy a , A.V. Goreglyada, E.V. Ivanov a , G. Inoue e , T. Kawai f , G.V. Kalmychkov a , K. Kashiwaya g , E.V. Kerber a , M.Yu. Khomutova a , G.K. Khursevich d , M.A. Krainov a , M.I. Kuzmin a , N.V. Kulagina b , P.P. Letunova a , K. Minoura h , Ts. Narantsetseg i , Yu.V. Osukhovskaya a , Ts. Oyunchimeg i , A.A. Prokopenko j , H. Sakai k , E.P. Solotchinac, L.L. Tkachenko a , D. Tomurhuu i
a Institute of Geochemistry, Siberian Branch of the RAS, 1a ul. Favorskogo, 664033, Irkutsk, Russia
b Institute of the Earth's Crust, Siberian Branch of the RAS, 128 ul. Lermontova, Irkutsk, 664033, Russia
c Institute of Geology and Mineralogy, Siberian Branch of the RAS, 3 prosp. Akad. Koptyuga, Novosibirsk, 630090, Russia
d Geological Institute, Belorussian Academy of Sciences, Minsk, Belorussia
e Ozuma Women's University, 2-8-1,Mejirodai,Bunkyou-ku, 112-8681, Tokyo, Japan
f Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8601, Japan
g Kanazawa University, Kakuma,Kanazawa,920-1192 Japan
h Tohoku University, Kashiwa-cho 3-54-2, Tachikawa, Tokyo, 190-0004, Japan
i Institute of Geology and Mineral Resources, Mongolian Academy of Sciences, Mongolia
j University of South Carolina, Columbia, SC 29208, USA
k Toyama University, 3190 Gofuku, Toyama 930-8555, Japan
Keywords: Bottom sediments; spore-pollen assemblages; Pleistocene; vegetation and climate change; Lake Hцvsgцl; Mongolia
Pages: 863-885

Abstract >>
A new experiment of the Hövsgöl Drilling Project was carried out in Lake Hövsgöl in 2004, as part of the international program of scientific drilling in the Baikal Rift. The reported data include a preliminary description of the recovered lake sediments (HDP-04 core), with their compositions and physical properties, and a tentative age-depth model based on the paleomagnetic polarity scale. This is the first evidence that the lithology of sediments deposited for the past ~1 Myr records periodic alternation of carbonate-free diatomaceous mud and carbonate-bearing silty clay.
The diatom intervals in the record are interpreted as corresponding to interglacials by analogy with the periodicity known since the Last Glacial. The core bears signature of at least nine lithological change events. The sediment lithology records extremely low stand of Paleo-Hövsgöl (shallow-water facies produced by erosion of older sediments at the point where the today's lake reaches a depth of 240 m). Correlation of the HDP-04 core data with reflection profiling evidence confirms the presence of quite a large gap in the Pleistocene sedimentary record from the Hövsgöl rift basin.
The discovery of alternating carbonate-rich/carbonate-free cycles and evidence for sudden lake level changes impart special importance to the Hövsgöl archive: It can provide a deeper insight into the regional water budget and humidity history than it has been so far possible for the Middle and Late Pleistocene.



2.
Chemical composition of pore waters of bottom sediments in different Baikal basins

T.V. Pogodaeva a , T.I. Zemskaya a , L.P. Golobokovaa, O.M. Khlystova, H. Minamib, H. Sakagamib
a Limnological Institute, Siberian Branch of the RAS, 3 ul. Ulan-Batorskaya, Irkutsk, 664033, Russia
b Research Center of New Energy Sources, Institute of Technologies, Koen-cho 165, Kitami 090-8507, Japan
Keywords: Pore waters; bottom sediments; ions; gas hydrates; Lake Baikal
Pages: 886-900

Abstract >>
Results of study of pore waters of bottom sediments from different Baikal basins are presented. The most typical ion distribution patterns reflecting the Baikal sediment diagenesis are given. We have established that in areas with regular sedimentation, in the absence of faults and inflows, the sediment pore waters of three lake basins inherit the chemical composition of the Baikal water, which is stable in time and space. Changes in pore water composition mark general natural anomalies, such as the presence of active faults, tectonic movements, and inflows along permeable zones. In areas with the subsurface occurrence of gas hydrates, thorough long-term research has revealed an anomalous composition of pore waters. It has been established that the anomalies are caused by a discharge of deep-level mud-volcanic fluids. The ejected mud-volcanic waters differ from each other in mineralization, ion composition, and sources, which determines the difference in hydrate formation and the composition of gas hydrates.



3.
Metasomatites of the Kara gold deposit (Eastern Transbaikalia)

Z.I. Kulikova, A.M. Spiridonov, L.D. Zorina
Institute of Geochemistry, Siberian Branch of the RAS, 1a ul. Favorskogo, Irkutsk, 664033, Russia
Keywords: Gold deposit; propylites; syn-ore metasomatites; zoning
Pages: 901-912

Abstract >>
Wall-rock metasomatites of the Kara gold deposit, a high-temperature medium-depth pneumatolytic-hydrothermal formation, have been studied. Gold mineralization is associated with the intrusion of granitoids of the Kara-Chacha massif (J3) and dikes of alkaline rocks (J3-K1), which include hybrid porphyries,



4.
Ore-magmatic systems and metallogeny of gold and silver in Northeastern Asia

G.N. Gamyanina, N.A. Goryachevb, N.E. Savva b
a Institute of Diamond and Noble-Metal Geology, Siberian Branch of the RAS, 39 prosp. Lenina, Yakutsk, 678980, Russia
b Northeastern Complex Research Institute, Far Eastern Branch of the RAS, 16 ul. Portovaya, Magadan, 685000, Russia
Keywords: Metallogenic belts; ore-magmatic systems; noble metals; types of mineralization
Pages: 913-922

Abstract >>
Regional ore-magmatic systems (OMS's) and metallogenic gold-silver belts in northeastern Asia are considered, with emphasis placed on their relationships owing to the effect of geodynamic settings and underlying and host rock sequences on the localization of gold and silver deposits of different types. Particular types of lithologic assemblages with specific mineralogical and geochemical features are persistent throughout the metallogenic belts, controlled by regional noble-metal OMS's. Regional OMS's with one-, two-, and multilevel local OMS's producing different types of noble-metal mineralization are described. The problem of mineral typomorphism in metallogenic analysis has been first raised. This analysis permits one to recognize indicators of ore formation (a particular genetic type of deposits, their formation and denudation levels), sources of ore-forming fluids, regional specific geochemistry and its relationship with magmatism. Regular presence of platinum in gold-bearing metallogenic zones is shown.



5.
Partitioning of species-forming and impurity cations among growth pyramids of pinacoid and prism faces in crystals of beryl, cordierite, and beryllian indialite

M.A. Mikhailov, T.V. Demina, O.Yu. Belozerova
Institute of Geochemistry, Siberian Branch of the RAS, 1a ul. Favorskogo, Irkutsk, 664033, Russia
Keywords: Crystals of compounds with beryl structure; face effect
Pages: 923-932

Abstract >>
The face effect was observed in all individual compounds with beryl structure having grown at a rate of 1-8 unit cells a second, with spontaneous crystallization in the system beryl (or cordierite)-Mg,Ca/Cl,F-impurity, where impurities are Ti, V, Cr and/or Fe oxides. By



6.
The Baikalian and Vendian sequences in the Lower Angara area ( southwestern Siberian Platform )

B.B. Kochnev, K.E. Nagovitsin, M.Sh. Faizullin
Institute of Petroleum Geology and Geophysics, Siberian Branch of the RAS, 3 prosp. Akad. Koptyuga, Novosibirsk, 630090, Russia
Keywords: Neoproterozoic; Vendian; Baikalian; microfossils; Chadobets uplift; Yenisei Range; Siberian Platform
Pages: 933-940

Abstract >>
In the section of Agaleevskaya BH-4 drilled in the lower reaches of the Angara River, Vendian and Baikalian sediment sequences have been recognized within Neoproterozoic strata. The Vendian sequence is formed by terrigenous-carbonate deposits of the Tetere, Soba, and Katanga Formations of the Danilovo Horizon, referred to as the Upper Vendian Nemakit-Daldyn Stage, as well as by terrigenous deposits of the Taseeva Group. The Baikalian Horizon is composed of the Brus Formation, earlier recognized only on the Chadobets uplift, and is separated from the Vendian deposits by a stratigraphic gap. In the Brus Formation, a microfossil complex similar to earlier described biotas of the Siberian Baikalian strata was found. The underlying deposits of the Terina Formation contain microfossils lacking below the basement of the Lakhanda Horizon (Neoproterozoic).



7.
Lower Cretaceous biostratigraphy of Northern Siberia: palynological units and their correlation significance

E.B. Pestchevitskaya
Institute of Petroleum Geology and Geophysics, Siberian Branch of the RAS, 3 prosp. Akad. Koptyuga, Novosibirsk, 630090, Russia
Keywords: Spore-pollen biostratigraphy; correlation; Berriasian-Barremian; West Siberia; East Siberia
Pages: 941-959

Abstract >>
The Berriasian-Barremian biostratigraphy based on spores and pollen of terrestrial plants found in sections from northern Siberia shows a succession of eight units. The ages of the units are proved by calibration against the Boreal zonal standard and their stratigraphic position is controlled by faunal and dinocyst records. The sections of the study are depth-stacked over one another, with partial overlap, and include several isochronous levels marked by the same palynological features. The levels are defined by changes in the taxonomic composition of spore-pollen assemblages found in the sections and recognized using published evidence from northern Siberia. Most of the identified boundaries of the palynostratigraphic units provide a good potential for northern Siberian regional correlation.



8.
Seismic stimulation of oil reservoirs

S.V. Serdyukov, M.V. Kurlenya
Mining Institute, Siberian Branch of the RAS, 54 Krasny prosp., Novosibirsk, 630091, Russia
Keywords: Producing formation; oil production; seismic stimulation; enhanced oil recovery; physical processes
Pages: 960-967

Abstract >>
Experimental studies of energy balance in low-field seismic stimulation of oil recovery show that producing formations can change their properties at the expense of internal energy activated by the applied seismic load. The suggested stimulation mechanism is based on the effect of low-amplitude waves on plastic strain in the formation as the latter becomes moved off its thermodynamic equilibrium by the production process. The suggested model explains many effects known from experiments which result from interplay of different physical processes.



9.
Nonlocal response functions in processing global electromagnetic data

V.V. Plotkin, A.Yu. Belinskaya, P.A. Gavrysh, A.I. Gubanov
Institute of Petroleum Geology and Geophysics, Siberian Branch of the RAS, 3 prosp. Akad. Koptyuga, Novosibirsk, 630090, Russia
Keywords: Upper mantle; global MVS; electrical conductivity; lateral inhomogeneity; nonlocal response functions; multipoint transfer operators
Pages: 968-975

Abstract >>
We discuss approaches to mapping lateral apparent conductivity variations at different periods from magnetic observatory data using multipoint transfer operators as nonlocal functions of the EM response. The multipoint operators provide correlation of three magnetic field components recorded at all observatories. The inversion procedure was applied to Sqobservatory data for 1964-68 and records of 30 magnetic storms for 1957-2001. To obtain lateral conductivity patterns, data on diurnal Sqvariations and global magnetic storms were processed with the spherical harmonic analysis. The same data were used to estimate the coefficients of first harmonics in the SH series of diurnal lateral variations of Earth's apparent conductivity.