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Russian Geology and Geophysics

2017 year, number 6

1.
PETROLOGY OF FOIDITIC AND MEYMECHITIC VOLCANISM IN THE MAIMECHA-KOTUI PROVINCE (Polar Siberia)

Yu.R. Vasilev1,2, M.P. Gora1, D.V. Kuzmin1,2
1V.S. Sobolev Institute of Geology and Mineralogy, Siberian Branch of the Russian Academy of Sciences, pr. Akademika Koptyuga 3, Novosibirsk, 630090, Russia
2Novosibirsk State University, ul. Pirogova 2, Novosibirsk, 630090, Russia
Keywords: Foidites, meymechites, melt inclusions, Arctic Siberia, Maimecha-Kotui province

Abstract >>
Comparative analysis of ultramafic meymechites of the Maimecha Suite and alkaline volcanics of the Ary-Dzhang Suite (foidites (nephelinites, analcimites, limburgites, etc.) and melilitites) has shown their consanguinity, which indicates their relationship with the same magmatic system periodically producing large amounts of alkaline ultramafic melts. We have studied the petrogeochemical and mineralogical compositions of rocks and melt inclusions in the hosted olivines. The rocks of the Maimecha and Ary-Dzhang Suite differ considerably in MgO content, which is well explained by the accumulation of olivine. The inclusions in olivines from the meymechites and the rocks of the Ary-Dzhang Suite correspond in composition to foidites. The trace and rare-earth element patterns are similar both in the foidites and meymechites and in the melt inclusions: They show negative anomalies of Rb and K and positive anomalies of Nb and Ta. The ratios of indicator elements (Nb/Ta, Ba/La, Ta/La, etc.) in the rocks of the Maimecha and Ary-Dzhang Suite are constant and almost independent of their Mg# values. The La/Yb ratio in the foidites is significantly higher than that in the meymechites and in the melt inclusions from their olivines, which indicates that the rocks of the Ary-Dzhang Suite resulted from the fractionation of highly magnesian alkaline picritoid melt.



2.
COMPOSITION AND GENESIS OF GARNET IN THE ROCKS OF PALEOPROTEROZOIC GNEISS-MIGMATITE COMPLEX (Sharyzhalgai uplift, southwestern Siberian craton)

O.M. Turkina1,2, V.P. Sukhorukov1,2
1S. Sobolev Institute of Geology and Mineralogy, Siberian Branch of the Russian Academy of Sciences, pr. Akademika Koptyuga 3, Novosibirsk, 630090, Russia
2Novosibirsk State University, ul. Pirogova 2, Novosibirsk, 630090, Russia
Keywords: Garnet, major- and trace-element zoning, paragneisses, migmatites, S-granites

Abstract >>
We present the results of study of garnet-bearing paragneisses, migmatites, and vein granites of migmatite-gneiss complex of the Irkut terrane (Sharyzhalgai uplift, southwestern Siberian craton), major- and trace-element zoning of the garnet, and the age and trace-element composition of zircon. The migmatite-gneiss complex of the Irkut terrane formed in the Paleoproterozoic, at 1.85-1.86 Ga. The maximum temperatures of metamorphism and partial melting evaluated with the Ti-in-zircon and Zr-in-rutile thermometers are 790-830 and 830-860 ºC, respectively. Three generations of garnet have been recognized according to texture and zoning: metamorphic, peritectic, and magmatic. Metamorphic generation forms the core of garnet in paragneisses and migmatites, contains numerous fine inclusions, and has the highest contents of grossular (Grs) component, HREE, and Y decreasing from core to rim, which agrees with the Rayleigh fractionation of compatible components. Peritectic garnet with large inclusions of quartz and feldspar is predominant in diatexites and in gneisses in contact with leucosome. It has almost constant low contents of Grs, HREE, and Y slightly increasing in the rim. Garnet in vein melanocratic granites is similar in composition to garnet in diatexites. Magmatic garnets in leucocratic granites are characterized by a decrease in the contents of Grs, HREE, and Y from core to rim and by a strong negative Eu anomaly. It seems to have resulted from the dissolution/precipitation of peritectic garnet in the melt. According to mineral and chemical compositions, the gneisses and migmatites are subdivided into high- and medium-alumina series produced through the melting of two source rocks, pelitic and graywacke, which is confirmed by their different REE patterns. The FeO and MgO enrichment of the granites relative to the melts of pelites and graywackes, the inherited contents of HREE in the diatexites and granites from paragneisses, and the presence of peritectic garnet in melanocratic granites evidence that the formation of granite was not accompanied by the effective segregation of garnet from the melt.



3.
REFLECTION OF HOLOCENE CLIMATIC CHANGES IN MINERALOGY OF BOTTOM SEDIMENTS FROM YARKOVSKY POOL OF LAKE CHANY (southern West Siberia)

A.N. Zhdanova1, E.P. Solotchina1, P.A. Solotchin1, S.K. Krivonogov1,2, I.V. Danilenko1
1V.S. Sobolev Institute of Geology and Mineralogy, Siberian Branch of the Russian Academy of Sciences, pr. Akademika Koptyuga 3, Novosibirsk, 630090, Russia
2Novosibirsk State University, ul. Pirogova 2, Novosibirsk, 630090, Russia
Keywords: Bottom sediments, carbonates, XRD analysis, IR spectroscopy, Holocene, paleoclimate, Lake Chany, West Siberia

Abstract >>
Sediments of lakes located in closed basins in inland areas are an excellent archive of environmental and climatic changes. One of such archives is the Chany lake system located in the Baraba steppe of southern West Siberia and comprising three associated lakes: Bolshie Chany, Malye Chany, and Yarkul, connected by watercourses. We present the first data on the mineral composition of the Holocene sediments of Yarkovsky Pool of Lake Bolshie Chany with predominantly carbonate sedimentation. The sediments were studied by X-ray diffraction (XRD), IR spectroscopy, electron microscopy, stable-isotope geochemistry (18O and 13C), laser granulometry, elemental analysis, and radioisotope dating. Mathematical modeling of complex XRD profiles of carbonate minerals in the sediments has revealed Mg-calcites with different Mg contents, excess-Ca dolomites, and aragonite. The obtained carbonate record gives an insight into the stratigraphic distribution of chemogenic carbonates, in which the number and proportion of phases are determined by the Mg/Ca ratio, salinity, and total alkalinity of the lake water. The phase proportions change depending on climatic cycles and lake level fluctuations. Comparison of the carbonate record with the lithologic data, d18O and δ13C values, and distribution of some geochemical indicators of depositional environments showed several stages of evolution of Yarkovsky Pool related to Holocene regional climatic changes.



4.
HYDROCARBON COMPOSITION OF BITUMEN FROM DEEPLY BURIED TERRESTRIAL ORGANIC MATTER (zone of apocatagenesis)

V.A. Kashirtsev1, K.V. Dolzhenko1, A.N. Fomin1,2, A.E. Kontorovich1,2, N.P. Shevchenko1
1A.A. Trofimuk Institute of Petroleum Geology and Geophysics, Siberian Branch of the Russian Academy of Sciences, pr. Akademika Koptyuga 3, Novosibirsk, 630090, Russia
2Novosibirsk State University, ul. Pirogova 2, Novosibirsk, 630090, Russia
Keywords: Vilyui syneclise, superdeep well SV-27, Permo-Carboniferous coal-bearing strata, meso- and apocatagenesis, vitrinite reflectance, biomarkers, alkenes, dimethylalkanes, asphaltene-occluded hydrocarbons

Abstract >>
We present new results on catagenetic alteration of dispersed organic matter (DOM) and individual hydrocarbon composition of bitumen extracts from the lower mesocatagenesis and apocatagenesis zone, based on the study of core samples from superdeep well SV-27 (Vilui syneclise), which penetrated Permian and Upper Carboniferous coal-bearing strata. The vitrinite reflectance data show a progressive increase in the thermal maturity of DOM at a depth of ~4 km. The major biomarker indicators of the thermal history of DOM in the central part of the Vilyui syneclise appear to play only a minor role below this depth, thus reflecting the early stages of mesocatagenesis. The pristane/phytane ratios begin to invert at the same depth. Bitumen extracts from core samples collected from this depth contain new hydrocarbons in trace amounts, which increase with depth. The identified compounds include homologous series of alkenes, 2,4- and 2,7-dimethylalkanes, and alkylcyclohexanes with a prevalence of compounds with an odd carbon number predominance. Unusual differentiation of aliphatic and cyclic hydrocarbons with even and odd carbon-numbered chains occurs at the maximum depth (6458 m). Among aromatic hydrocarbons, four new diastereomers are identified: 17-desmethyl-23-methylmonoaromatic steroids C27. Considerable variations in the composition of bitumen extracts from the apocatagenetically altered core samples appear to reflect the termination of hydrocarbon generation from kerogen and further thermolysis of residual bitumens, including their asphaltene components. This explains the low values of maturity biomarker indicators corresponding to the apocatagenesis grade, since in this case they reflect the composition of hydrocarbons generated during the early stages and later occluded and adsorbed by asphaltenes. Deep-seated micro-oil did not participate in the formation of oil rims and major gas condensate pools in the Vilyui petroleum area.



5.
DEPTH DIFFERENTIATION OF THE MIDDLE ORDOVICIAN GRAPTOLITE AND TRILOBITE COMPLEXES OF GORNY ALTAI

N.V. Sennikov1, A.V. Timokhin2, E.V. Lykova2
1Novosibirsk State University, pr. Akademika Koptyuga 3, Novosibirsk, 630090, Russia
2A.A. Trofimuk Institute of Petroleum Geology and Geophysics, Siberian Branch of the Russian Academy of Sciences, pr. Akademika Koptyuga 3, Novosibirsk, 630090, Russia
Keywords: Ordovician, graptolites, trilobites, biofacies and lithofacies analyses, paleobasin depths, Gorny Altai

Abstract >>
A biostratigraphic analysis of the Middle Ordovician reference sections of northeastern Gorny Altai is carried out. We study complexes of pelagic graptolites and benthic trilobites from the Dapingian-Darriwilian Tuloi and Karasu Formations. For the first time for the Late Paleozoic sedimentary basins of Siberia, lithofacies and biofacies analyses of the sedimentary successions and associated paleobiota are applied to estimation of the depths of the shelf basin and the remoteness of its particular parts from the shoreline. Proposed reconstructions are based on a complex analysis of the lithology and thickness of the successions and on the structure of associated complexes of pelagic organisms, graptolites (including evaluation of the population density and dominating taxa). Herein we appraise the bioindicator potential of the benthic trilobite paleocommunities.



6.
ACOUSTIC PROPERTIES OF HYDRATE-BEARING SAND SAMPLES: LABORATORY MEASUREMENTS (setup, methods, and results)

A.D. Duchkov1, A.A. Duchkov1,2, M.E. Permyakov1, A.Yu. Manakov3,2, N.A. Golikov1, A.N. Drobchik1
1A.A. Trofimuk Institute of Petroleum Geology and Geophysics, Siberian Branch of the Russian Academy of Sciences, pr. Akademika Koptyuga 3, Novosibirsk, 630090, Russia
2Novosibirsk State University, ul. Pirogova 2, Novosibirsk, 630090, Russia
3A.V. Nikolaev Institute of Inorganic Chemistry, Siberian Branch of the Russian Academy of Sciences, pr. Lavrentieva 3, Novosibirsk, 630090, Russia
Keywords: Hydrate-bearing samples, laboratory acoustic measurements, acoustic properties

Abstract >>
A new system has been designed for laboratory physical modeling of hydrate-bearing sand samples and measuring their acoustic properties at different temperatures and pressures. The system includes a pressure vessel, units of temperature control, external pressure, and gas/liquid delivery, and a unit for measuring velocities of acoustic waves. Measurements are carried out in 10-50 mm high cylindrical specimens 30 mm in diameter. The system provides methane hydrate formation in sand samples and their acoustic measurements for as long as several days due to automatic control. Hydrate-bearing samples are prepared by pressurized methane injection into pores of wet sand and are exposed to several cooling/heating cycles to increase hydrate formation rates. Hydrate-bearing samples have been prepared and travel times of acoustic P and S waves have been measured in dozens of successful experiments. Acoustic data confirm the formation of hydrates, with the related increase in wave velocities to values about those in frozen sediments. The prepared gas hydrates are inferred to be of cementing type, i.e., they form as cement at the boundaries of mineral grains. The obtained velocities of acoustic waves show a positive linear correlation with hydrate contents in sand samples.



7.
FRACTURE IN HETEROGENEOUS MATERIALS: EXPERIMENTAL AND THEORETICAL STUDIES

V.S. Kuksenko, Kh.F. Makhmudov
Ioffe Institute, Russian Academy of Sciences, St. Petersburg, 194021, Russia
Keywords: Zone of brittle failure, fracture, prediction, acoustic emission, fracture source, microseismic monitoring

Abstract >>
The kinetics of fracture in stressed heterogeneous materials is investigated in a differentiated way using the parameter Δ t , the interval between single or multiple (cooperative) microfracture events recorded by acoustic emission (AE) responses. The patterns of fracture nucleation and growth, which is a statistic process, are controlled by the heterogeneity of deforming material. There are two important aspects revealed by the study: 1) structural heterogeneity of materials causes uneven distribution of stress in loaded solids and thus creates local zones of microstress and ensuing microfracture in the overstressed zones; 2) AE measurements and microseismic monitoring are applicable to prediction of fracture by locating its source and thus allows predicting related hazard in mines, tunnels, bridges, nuclear-power plants, and other important engineering objects.



8.
WAVE TRANSFORMS OF TRANSIENT ELECTROMAGNETIC FIELD IN CONDUCTIVE EARTH

G.A. Gretskov1, M.I. Epov1,2, E.Yu. Antonov1
1A.A. Trofimuk Institute of Petroleum Geology and Geophysics, Siberian Branch of the Russian Academy of Sciences, pr. Akademika Koptyuga 3, Novosibirsk, 630090, Russia
2Novosibirsk State University, ul. Pirogova 2, Novosibirsk, 630090, Russia
Keywords: TEM soundings, wave transform, regularization

Abstract >>
The study aims at finding a stable method for transformation of time-domain electromagnetic diffusion field to an electromagnetic wavefield. Two ways of transformation are considered: singular-value decomposition (SVD) and Tikhonovs regularizations. Transformation is applied to TEM responses of a conductive half-space, a conductive S film, and to a series of horizontally layered models. The wave transforms are used to plot travel-time curves and to estimate the velocity of EM field propagation.



9.
JOINT INVERSION OF INDUCTION AND GALVANIC LOGGING DATA IN AXISYMMETRIC GEOLOGICAL MODELS

I.V. Mikhaylov1,2, V.N. Glinskikh1,2, M.N. Nikitenko1, I.V. Surodina1,3
1A.A. Trofimuk Institute of Petroleum Geology and Geophysics, Siberian Branch of the Russian Academy of Sciences, pr. Akademika Koptyuga 3, Novosibirsk, 630090, Russia
2Novosibirsk State University, ul. Pirogova 2, Novosibirsk, 630090, Russia
3Institute of Computational Mathematics and Mathematical Geophysics, Siberian Branch of the Russian Academy of Sciences, pr. Akademika Lavrent'eva 6, Novosibirsk, 630090, Russia
Keywords: Joint inversion, electrical logging, VEMKZ, BKZ, axisymmetric model, electrical resistivity

Abstract >>
We have developed a computational algorithm for joint inversion of array induction and galvanic data in 2D models. It is based on the finite-difference solver and nonlinear minimization and is designed to develop realistic geoelectrical models of complex fluid-saturated formations. The algorithm is tested and verified on noisy synthetic induction and galvanic data. The obtained 2D inversion results are compared with those corresponding to the traditional 1D radial approach. The developed algorithm was used to conduct joint 2D inversion of VEMKZ and BKZ logs from the Fedorovskoe and Vostochno-Surgutskoe oil fields in the E-W striking Ob River area.



10.
PARAMETRIC METHOD OF COMPENSATION FOR NEAR-SURFACE HETEROGENEITY IN PROCESSING CDP DATA

A.P. Sysoev, G.D. Gorelik
National Mining University Gornyi, 21 liniya 2, St. Petersburg, 199106, Russia
Keywords: Seismic reflection method, near-surface heterogeneity, variable ground surface topography, root-mean-square velocity

Abstract >>
Compensation for near-surface heterogeneity is an important part of the seismic reflection method. The problem is solved by continuing the observed wavefield to a horizontal datum. Traditionally, two reflection traveltime curves determined from survey and datum lines are related by static shift corrections. In this paper, we solve a continuation problem in which the relation between the traveltimes of the observed and continued wavefields is given by the root-mean-square velocity equation for a two-layer earth model. A comparative analysis is made for the two methods of compensation for surface heterogeneity due to the variable altitude of the ground surface.