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Russian Geology and Geophysics

2010 year, number 2

1.
SEDIMENTOGENESIS AND RESOURCE POTENTIAL OF MIDDLEUPPER BATHONIAN RESERVOIRS IN THE MIDDLE OB REGION

A.E. Kontorovicha, L.G. Vakulenkoa, V.A. Kazanenkova, M.B. Skvortsovb, P.A. Yana, V.V. Bykovb, A.Yu. Popova, and L.S. Saenkoa
aA.A. Trofimuk Institute of Petroleum Geology and Geophysics, Siberian Branch of the Russian Academy of Sciences, 3 prosp. Acad. Koptyuga, Novosibirsk, 630090, Russia
bRosneft, 26/1 Sofiyskaya nab., Moscow, 115035, Russia
Keywords: Lithology, depositional environment, reservoirs, petroleum potential, Middle Jurassic, West Siberia
Pages: 147-158

Abstract >>
This study provides a comprehensive sedimentologic analysis of the J2 prospective horizon (MiddleLate Bathonian) in the central West Siberian Basin. Based on the extensive dataset, it was established that structural complexity of this horizon is largely caused by a variety of depositional environments. Sedimentary facies of this horizon pass upward from widespread continental at the base, through deltaic or coastal-continental, to marginal-marine at the top. Change in the paleohypsometry of the study area reflects the distribution of depositional environments, in terms of the proportions of continental, transitional, and marine deposits. The study also shows that facies variability and change in depositional settings can have a significant control on reservoir quality, as well as its vertical and lateral distribution. Using a combination of detailed GDE reconstructions, structure contour mapping on the top and base of the J2 horizon, analyses of well test data, probability of reservoir presence, distribution of average porosity and permeability within different subenvironments, a composite map showing variations in the reservoir effectiveness in the J2 horizon was generated.



2.
DISTRIBUTION OF HYDROCARBON ACCUMULATIONS IN A BASIN: A MATHEMATICAL MODEL FOR THE WEST SIBERIAN PETROLEUM PROVINCE

V.R. Livshits
A.A. Trofimuk Institute of Petroleum Geology and Geophysics, Siberian Branch of the Russian Academy of Sciences, 3 prosp. Akad. Koptyuga, Novosibirsk, 630090, Russia
Keywords: Petroleum basin, basin modeling, point random process, Poisson process, Monte-Carlo simulation
Pages: 159-162

Abstract >>
The distribution of hydrocarbon accumulations in a basin is modeled as a nonstationary Poisson field of points with the average density of accumulations as a function of distance fr om the basin margin. The model, in which this distance is a unique parameter to define the intensity function, is suitable, in a first approximation, for Monte-Carlo simulation of the real pattern of accumulations. The Poisson random field of points is described with a power function, wh ere the power is a fractal dimension used as an integral numerical parameter of the distribution.



3.
THE LATE PLEISTOCENEHOLOCENE CLIMATE HISTORY IN THE WESTERN TODZHA BASIN ( Eastern Tuva )

S.G. Arzhannikova, S.V. Alekseeva, A.V. Glyzinb, N.V. Kulaginaa, N.V. Ignatovaa, and L.A. Orlovac
a Institute of the Earth's Crust, Siberian Branch of the Russian Academy of Sciences, 128 ul. Lermontova, Irkutsk, 664033, Russia
bMuseum of Lake Baikal, Siberian Branch of the Russian Academy of Sciences, 1 ul. Akademicheskaya, Listvyanka, 664520, Russia
cV.S. Sobolev Institute of Geology and Mineralogy, Siberian Branch of the Russian Academy of Sciences, 3 prosp. Akad. Koptyuga, Novosibirsk, 630090, Russia
Keywords: Paleoearthquake, damlake, lacustrine-fluvial deposits, fossil soil, frozen ground, ice wedge, Eastern Tuva
Pages: 163-175

Abstract >>
The Late Quaternary history of climate and deposition environments in the western Todzha basin has been reconstructed fr om the respective lacustrine and fluvial deposits. Data from sedimentary sections have provided clues to the causes and timing of sudden deposition changes, including those associated with Holocene tectonic activity in the Taskyl fault. Especially informative are permafrost, diatom, spore-pollen, and tree-ring data from a section at the Merzlyi Yar locality, wh ere frozen ground has preserved the pristine rhythmic pattern of sediments. The Merzlyi Yar section stores a record of dramatic consequences of large earthquakes generated by the fault, which produced a large damlake. The revealed pattern of discontinuous limnic deposition, with prominent tree markers and syngenetic ice wedges, places exact constraints on the stratigraphy of the section and allows its correlation with Holocene climate events within the intervals of fossil soils and vegetation.



4.
COBALT BEHAVIOR DURING NATURAL AND TECHNOGENIC OXIDATIVE LEACHING OF Co-CONTAINING PYRITES ( Letnee chalcopyrite deposit, Southern Urals )

O.L. Gaskova, E.V. Belogubb, and D.V. Makarovc
a V.S. Sobolev Institute of Geology and Mineralogy, Siberian Branch, Russian Academy of Sciences, 3 prosp. Akad. Koptyuga, Novosibirsk, 630090, Russia
b Institute of Mineralogy, Ural Division, Russian Academy of Sciences, Miass, Chelyabinsk oblast, 456317, Russia
c I.V. Tananaev Institute of Chemistry and Technology of Rare Elements and Minerals, Kola Scientific Center, Russian Academy of Sciences, 26a ul. Fersmana, Apatity, Murmansk oblast, 184209, Russia
Keywords: Cobalt, pyrite deposits, oxidation zone, sulfate minerals, oxidative leaching, thermodynamic model
Pages: 176-185

Abstract >>
Cobalt behavior during the oxidation of sulfide ores, unlike that during the oxidation of Co ores, is poorly known. Moreover, cobalt sulfates are rare in the world. Complex hydrous Co-containing and cobalt sulfates have been found in technogenic zones at the Letnee chalcopyrite deposit (Southern Urals). They have been identified at pit bottoms, in the ore stockpile, as well as directly on ore fragments and the evaporation barriers of underdump water puddles. The paper reports the first experimental data on the oxidative leaching of Co-containing sulfide ores in the laboratory. Also, parts of a thermodynamic model for behavior in oxidized zones are presented.
Experiments have revealed an increase in acidity up to pH = 4.14, along with transport of sulfate sulfur and metals into solution. They suggest acid mine drainage during the development of the Letnee deposit. The published stability diagrams for hydrous Cu, Mg, Zn, Co, and Ni sulfates were analyzed and compared with mineralogical finds in a technogenic oxidized zone. This made it possible to explain the precipitation sequence of minerals from solutions during their concentration by evaporation. As salts of these elements are highly soluble, significant contents of toxic metals inevitably remain in equilibrium solution, necessitating additional waste-water treatment (for example, creating sorption geochemical barriers). Therefore, the paper describes regularities in Co behavior during its sorption on solid phases.



5.
THE AGE OF METAMORPHISM OF SILLIMANITE-BEARING SCHISTS AT THE KYAKHTINSKOE DEPOSIT ( southwestern Transbaikalia )

I.A. Izbrodina, G.S. Rippa, A.G. Doroshkevicha, S.A. Sergeevb, D.I. Matukovb, and V.F. Posokhova
aGeological Institute, Siberian Branch of the Russian Academy of Sciences, 6a ul. Sakh'yanovoi, Ulan Ude, 670047, Russia
bCenter of Isotopic Research, A.P. Karpinsky Russian Geological Research Institute, 74 Srednii prosp., St. Petersburg, 199106, Russia
Keywords: Sillimanite schists, zircon, U-Pb (SHRIMP-II), geochronology, Late Mesozoic, southwestern Transbaikalia
Pages: 186-189

Abstract >>
Results of U-Pb (SHRIMP-II) and Rb-Sr dating of sillimanite schists in southwestern Transbaikalia are presented, which testify to high-temperature metamorphism in the Late Mesozoic. The metamorphism might have been related to the formation of metamorphic cores or tectonoplutonic activity accompanied by the formation of rift structures in Transbaikalia and Mongolia.



6.
ECLOGITES OF THE LATE CAMBRIAN-EARLY ORDOVICIAN NORTH KOKCHETAV TECTONIC ZONE ( northern Kazakhstan ): STRUCTURAL POSITION AND PETROLOGY

F.I. Zhimulev, M.A. Poltaranina, A.V. Korsakov, M.M. Buslov, N.V. Druzyaka, and A.V. Travin
V.S. Sobolev Institute of Geology and Mineralogy, Siberian Branch of the Russian Academy of Sciences, 3 prosp. Koptyuga, Novosibirsk, 630090, Russia
Keywords: Eclogites, symplectites, Ar-Ar dating, tectonic sheets, North Kokchetav tectonic zone
Pages: 190-203

Abstract >>
We consider the structural position and petrology of eclogites in the North Kokchetav accretion-collision zone located north of the Kokchetav metamorphic belt formed by high- and ultrahigh-pressure rocks. In the Early Ordovician North Kokchetav tectonic zone, thin sheets of mylonite and diaphthoric gneisses with eclogites are tectonically conjugate with the volcanic and sedimentary rocks of the Stepnyak paleoisland-arc zone. Eclogites have been revealed at two sites of the North Kokchetav tectonic zone Chaikino and Borovoe. The Chaikino eclogites formed at 800850 C and 1820 kbar, and the Borovoe eclogites, at 750800 C and 1718 kbar. Study of pyroxene-plagioclase symplectite replacing omphacite of the eclogites at both sites has recognized three stages of regressive magmatism: (1) formation of coarse-grained clinopyroxene-plagioclase symplectite at 760790 C and 1112 kbar, (2) formation of fine-grained clinopyroxene-plagioclase symplectite at 700730 C and 78 kbar, and (3) amphibolization of pyroxene at 570600 C and 56 kbar. The Ar-Ar age of muscovite from the Borovoe mica schists hosting eclogites is 493 ± 5 Ma, which corresponds to the time of cooling of metamorphic rocks to <370 C. Hence, the peak of high-pressure metamorphism and all recognized stages of retrograde changes are dated to the Cambrian. The geological data evidence that eclogite-schist-gneiss sheets were localized in the accretion-collision zone and became conjugate with sedimentary and volcanic rocks no later than in the Middle Ordovician.



7.
TEM SOUNDINGS IN MAGNETIC MEDIA

M.I. Epov and G.M. Morozova
A.A. Trofimuk Institute of Petroleum Geology and Geophysics, Siberian Branch of the Russian Academy of Sciences, 3 prosp. Akad. Koptyuga, Novosibirsk, 630090, Russia
Keywords: TEM soundings, ferromagnetics, electromagnetic induction, hysteresis
Pages: 204-208

Abstract >>
TEM responses of conducting ferromagnetic materials to a complex current pulse have been modeled for a magnetic cylinder typical of well casing. The behavior of the responses is investigated as a function of different model parameters.



8.
ESTIMATION OF HEAT FLOW IN TUVA FROM DATA ON HELIUM ISOTOPES IN THERMAL MINERAL SPRINGS

A.D. Duchkov, K.M. Rychkovab, V.I. Lebedevb, I.L. Kamenskiic, and L.S. Sokolova
aA.A. Trofimuk Institute of Petroleum Geology and Geophysics, Siberian Branch of the Russian Academy of Sciences, 3 prosp. Koptyuga, Novosibirsk, 630090, Russia
bTuvinian Institute of Complex Exploration of Natural Resources, Siberian Branch of the Russian Academy of Sciences, 117a ul. Internatsional'naya, Kyzyl, 667009, Russia
cGeological Institute, Kola Scientific Center of the Russian Academy of Sciences, 14 ul. Fersmana, Apatity, 184200, Russia
Keywords: Thermal mineral springs, helium in fluids, helium isotopes, heat flow, deep-level temperatures, Tuva
Pages: 209-219

Abstract >>
Concentrations of helium isotopes were measured in gas and water samples from 28 thermal mineral springs in Tuva and adjacent regions of Buryatia and Gorny Altai. It is shown that fluids from 16 springs are rich in mantle helium (435%). With regard to the air contamination of the samples, the corrected ratios of helium isotopes (R cor = 3He/4He) in these springs vary from 5.3·108 to 422·108. Using these Rcor values, we estimated the heat flow; these estimates were then applied to calculate the deep-level temperatures and thickness of thermal lithosphere. According to these parameters, the Tuva region is divided into two parts. Eastern Tuva (from ~96o E to the boundary with Buryatia) is characterized by abnormal helium isotope ratios and heat flow values indicating the intense heating of the Earths crust in eastern Tuva. At a depth of 50 km, a temperature reaches 10001200 oC, and the thickness of thermal lithosphere is reduced to 7050 km. This testifies to a rift process west (probably, up to 96o E) of the Baikal Rift Zone. In western Tuva, the average heat flow is much lower, ~4550 mW/m2, which is commensurate with that in the Altai-Sayan folded area as a whole. The deep-level temperatures here are twice lower, and the lithosphere thickness increases to 150 km.



9.
RADON AS A TRACER OF TECTONIC MOVEMENTS

V.I. Utkin and A.K. Yurkov
Institute of Geophysics, Ural Branch of the Russian Academy of Sciences, 100 ul. Amundsena, Yekaterinburg, 620016, Russia
Keywords: Soil-gas radon surveys, strain, earthquake nucleation
Pages: 220-227

Abstract >>
We suggest a model of radon emanation under compression or extension strain from a medium equivalent to rocks containing pores and cracks. The model is shown in several examples to be suitable for simulating the nucleation of rock bursts in deep mines and earthquakes. According to correlation of strain and radon measurements at the same sites, a relative strain change of n · 10-7 corresponds to a 200 % change of radon activity concentration. This high sensitivity means that radon data can be good tracers of tectonic movements.



10.
NOTES ON THREE EARTHQUAKES IN SANTIAGO DE CUBA (14.10.1800, 18.09.1826, 07.07.1842)

M.O. Cotilla and D. Cordoba
Departamento de Fisica de la Tierra y Astrofisica 1, Facultad de Ciencias Fisicas, Universidad Complutense de Madrid, Ciudad Universitaria, s/n 28040 Madrid, Spain
Keywords: Earthquake damage, historical seismicity, intensity, Santiago de Cuba, Cuba
Pages: 228-237

Abstract >>
Damage and parameters of the earthquakes of October 14, 1800, September 18, 1826, and July 7, 1842, in Santiago de Cuba, southeastern Cuba, have been studied. A quantitative re-evaluation of the size of the events is not feasible due to a lack of data. Hence, we have reinterpreted existing data to establish likely intensities and determine the epicentral region of occurrence. Available data do not permit accurate depth determinations. Intensities estimated from contemporary documentary sources give maximum values of 8, 89, and 9 (MSK scale), respectively. These seismic shocks were located in the Southeastern Seismotectonic Province of Cuba, CaribbeanNorth American Plate Boundary Zone. The earthquakes are associated with the Oriente fault system.