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2018 year, number
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S.B. Bortnikova1, O.L. Gaskova2, A.A. Tomilenko2, A.L. Makas1, E.A. Fursenko1, N.A. Palchik2, I.V. Danilenko2, N.A. Abrosimova1
1V.S. Sobolev Institute of Geology and Mineralogy, Siberian Branch of the Russian Academy of Sciences, pr. Akademika Koptyuga 3, Novosibirsk, 630090, Russia
2Trofimuk Institute of Petroleum Geology and Geophysics, Siberian Branch of the Russian Academy of Sciences, pr. Akademika Koptyuga 3, Novosibirsk, 630090, Russia
Keywords: gas-liquid inclusions, interstitial environment, stored waste
Abstract >>
The article presents the results of studies of inclusions in secondary sulfates (antlerite, a mixture of copiapite and coquimbite) and arsenates (erythrite and picropharmacolite) formed on the surface of technogenic bodies - stored waste from the enrichment of sulfide (Belovo and Ursk waste heaps) and arsenide (disposal maps of the Tuvacobalt plant) ores. A wide range of components have been identified in the composition of gas-liquid inclusions (GLI), the main ones being water and carbon dioxide. Hydrocarbons, O-containing organic compounds, N- and S-containing gases were found in smaller but measurable quantities. Arsine H3As was also found in inclusions of picropharmacolite (calcium and magnesium arsenate-arsenite). GLI of secondary minerals are a reflection of the composition of the interstitial environment in the waste body with one or another access of atmospheric gases, entering in free form and with seasonal precipitation into the waste body. The combination of locally generated and permeating gases determines the diversity of inorganic and biotic interactions in technogenic bodies. The presence of hydrocarbons and O-containing organic compounds is most likely associated with bacterial transformations of organic matter (residues of vegetation, wood, microalgae, fungi). At the same time, compounds such as carbon disulfide and sulfur dioxide indicate active inorganic reactions of decomposition of the sulfide matrix.
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V.L.Tauson, S.V.Lipko, D.N.Babkin, N.V.Smagunov, O.Yu.Belozerova, E.V.Kaneva
A.P. Vinogradov Institute of Geochemistry, Siberian Branch of the Russian Academy of Sciences, Irkutsk, Russia
Keywords: experiment, silver, gold, tin, sphalerite, hydrothermal systems
Abstract >>
Au-Ag mineralization occurrences in sphalerite ores of hydrothermal genesis are paradoxical in view of the incompatibility of these elements in sphalerite. The formation of sphalerite with Au and Ag impurities under hydrothermal crystallization of ZnS at 450 oC and 1kbar pressure was studied experimentally. Sn impurity was taken as a source of point defects in crystals modelling the interaction of Au and Ag with vacancies. The Ag solubility in low-Fe sphalerite is estimated as 3.80.7 g/g, Au ̶ ≤0.6 g/g. The main forms of Ag and Au occurrence in sphalerite are the inclusions of (Ag,Au)xS phases with x varies mainly from 1.8 to 2, and Au varies from 0.01 to 0.75 a.p.f.u. The primary forms of the elements in ores might be the microinclusions (Ag,Au)1.8-2.1S or close to (Ag,Au)S at higher fS2. In presence of Sn, the solubilities of Au and Ag become higher. The Au behavior corresponds to the substitution reaction Sn4+ + Au+ + v‒ ↔ 2 Zn2+ under the presence of two types of vacancy defects (v-) ‒ the inherent vacancies dependent on the crystallization conditions and the vacancies accompanying Sn4+
incorporation. Ag entrance is seemingly more dependent on fS2 conditions and does not correlate with Sn. The extra vacancies arise because of metastable crystallization under the conditions of oversaturation of growth medium. This is supported by the spherulite morphology of growth products and the admixture of wurtzite ZnS form. The elevation of distribution and
cocrystallization coefficients are observed for both noble metals (NM), upon that Au changes from incompatible to the category of highly compatible elements in sphalerite. The geochemical environments favorable for the formation of imperfect mineral crystals are considered. Such crystals are capable to uptake NM and other incompatible in ideal crystal elements because of their interaction with vacancies, both constitutional (inherent to the substance) and non-equilibrium defects, and surficial nano-sized formations (nonautonomous
phases). The evolution of these initially invisible forms of NM under metamorphic processes and remobilization of ore substance may result in Au and Ag escape and aggregation into microparticles.
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A.V. Poletayev, Y.V. Poletayeva
Oil and Gas Institute, Ministry of Science and Education Republic of Azerbaijan, Baku, Azerbaijan
Keywords: South Caspian depression, gas, formation, estimation, hydrocarbon.
Abstract >>
Maps of isotope composition changes according to area extent, as well as graphs of HC distribution depending upon stratigraphic age, including rocks, graphs of isotope composition change on sampling depth were compiled for HC study and oil-gas deposits formation. Gases genesis according to M. Shoelle and A. James methodic were studied. Two stages of formation were distinguished as a result of gases study of various forms of their manifestation. The first stage has begun in the underlying PS deposits and continued up to PS deposits. At this stage one various kind of tectonic fluctuations can observed. The second stage of HC formation has started from PS and characterized with a change of geodynamic conditions in region. Avalanche sedimentation, predominance of descending movements over ascending ones promoted the accumulation of thick sediments in PS age. As a result of sediments accumulation and tectonic processes (down warping) in the deep-seated basin led to the complication of thermobaric conditions in the sedimentary series. There were determined basic ways of HC migration as well as estimated oil-gas content prospective. The results of the gas survey within the deep-water part of the South Caspian were considered in detail and it was established that for this zone gas generation is typical, with the predominance of two components - methane and ethane. Study of HC migration trend in time and area as well as areas of generation etc. allows to reveal some structures where there is evidence of HC accumulation with large and gigantic reserves. It was established that hydrocarbon gases in bottom sediments and sediments of the upper part of the South Caspian section are closely related to the sources of hydrocarbon formation, migration and other processes occurring in deeply buried sediments, as well as in upper part of the section.
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D.D. Byzov, P.S. Martyshko, I.V. Ladovskii, A.G. Tsidaev
Institute of Geophysics, Ural Branch of the Russian Academy of Science
Abstract >>
density sections from seismic profiles, three-dimensional interpolated density model, linear inverse gravimetry problem, correctness class for two-dimensional density equivalents, layer-by-layer filtering of the observed field, lithostatic pressure anomalies, zoning of geological structures
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A. Ali, S. Ullah
Department of Geology, University of Peshawar, Pakistan
Keywords: Patala Formation; Upper Indus Basin; Smectite illitization; Geothermometry; R3 zone
Abstract >>
Smectite illitization geothermometry has been used to assess the thermal maturity and hydrocarbon generation potential of the Late Paleocene to Early Eocene Patala Formation in the Upper Indus Basin. X-ray diffraction (XRD) detected illite, muscovite, quartz, kaolinite, chlorite, and calcite. Comparison between air-dried (AD) and ethylene glycol (EG)-solvated XRD patterns reveal the absence of discrete smectite and interstratified illite-smectite (I-Sm). Additionally, authigenic illite-2M1
indicates that the Patala Formation has entered a late-stage diagenetic zone or low anchizone which lies in the R3 illitization zone. Abundant SiO2
and Al2O3 in the Patala clay fraction indicate the substitution of tetrahedral Si4+ by Al3+
within the smectite interlayers. Likewise, the relative abundance of K2O to CaO and MgO indicates the exchange of K+ with Ca2+ and Mg2+ during smectite illitization. Scanning electron microscopy (SEM) reveals in-situ growth of platy illite crystals that form
within the R3 zone. Furthermore, the total organic carbon (TOC) of the Patala shale exposed in Tirah suggests
a poor to good source rock. The absence of
discrete smectite and I-Sm,
combined with the detection of discrete illite in the Patala shale, suggests
that hydrocarbon might have
potentially migrated from the source to the reservoir rock during
smectite illitization.
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A. Kamal1, M. M. Shah1, H.U. Rahim1,2,*, T. Zafar3, R. Khalil4, M. Shahzeb1, M. S. Ahmed5, M. Sami6,7
1Department of Earth Sciences, Quaid-i-Azam University, Islamabad 45320, Pakistan
2Earth Sciences Division, Pakistan Museum of Natural History, Islamabad 44000, Pakistan
3Institute of Geochemistry, Chinese Academy of Sciences, Guiyang, 550081, China
4Faculty of Earth Sciences, King Abdulaziz University, Jeddah 21589, Saudi Arabia
5Geology and Geophysics Department, College of Science, King Saud University, Riyadh 11451, Saudi Arabia
6Geosciences Department, College of Sciences, United Arab Emirates University, 15551, Al-Ain, United Arab Emirates
7Geology Department, Faculty of Sciences, Minia University, Al-Minia, 61519, Egypt
Keywords: Dolomites, Samana Suk Formation (SMSF), Middle Jurassic, Petrography, Stable Isotopes
Abstract >>
Diagenetically modified carbonate rocks are more common in the rock record. Among these modifications, multiphase dolomitization is the most common process. The Middle Jurassic carbonates of the SMSF are extensively altered by the dolomitization process in the Kahi Section, Nizampur Basin. The primary objective of this study is to investigate this multiphase dolomitization and to elucidate its possible mechanism.
Field investigation show both host limestone (oolitic, fossiliferous and massive) and dolomites. Dolomite bodies are of both bedding parallel and cross cutting the bedding planes. Different types of dolomites were recognized on the basis of color contrast as dark grey colour replacive dolomite, light grey dolomite, brownish dolomite and yellowish dolomite. Beside replacive phase voids and fracture filling cementing saddle dolomite, and cementing calcites are also recognized in the field. Petrographic studies show the complex diagenetic history of Samana Suk Formation from near surface diagenesis including micritization, neomorphism and several varieties of dolomites. These varieties are: RD1 is very fine to fine grained dolomite, RD2 is medium to coarse grained and anhedral to subhedral dolomite, RD3 is coarse to very coarse grained and planner euhedral zoned dolomite and RD4 is coarse grained euhedral to subhedral ferroan dolomite. In addition, cementing saddle dolomite SD have large crystal, curved faces with sweeping extinction. cementing calcite phases are CC1 is granular mosaic, CC2 is twin CC3 is fracture filling and CC4 is ferroan calcite. The stable isotope values of limestone (δ18O: -7.13 to -0.73 V-PDB and δ13C: -0.05 to 1.32 V-PDB) showing depletion in from the Jurassic marine signature. The multiphase dolomites RD1-RD4, SD values (δ18O: -8.65 to -3.16 and δ13C: -3.56 to +2.09) indicate multiphase dolomitization. The C1-C3 values (δ18O: -11.07 to -8.97 and δ13C: -2.14 to +0.76) indicate highly depleted values of δ18O showing its source from the hydrothermal origin. From field, petrography and geochemistry data it is deduced that possible source of the Mg for hydrothermal dolomites is through activation of faults and fractures during active tectonic regime in the area and can be related to activation and reactivation of Kahi Thrust system.
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A.S. Dushin1,2, A.N. Lubochko1, I.S. Krivoshchekov1, A.N. Inozemtsev3
1 RN-BashNIPIneft, Ufa, Russia
2 UFA State Petroleum Technological University, Ufa, Russia
3 Roxar Paradigm - Software Solutions, Moscow, Russia
Keywords: Organogenic structures, facies heterogeneity, carbonate rocks, ES360 full-azimuth angular migration, horizontal transverse (HTI) anisotropy, acoustic scanner, diffractive and scattered components, fractures, vugginess
Abstract >>
The work shows a solution to the problem of searching for cavernous-fractured zones, as well as zones that determine reservoir heterogeneity in the Frasnian-Famennian deposits, of one of the licensed areas of the Republic of Bashkortostan. This article describes the application of complex approach to the study of azimuthal horizontal transverse isotropy of rock, using well data and modern methods of processing areal seismic data for carbonate deposits associated with the development of organogenic structures. The results of using the full-azimuth angular migration technology are described.
Implementation of high-tech approaches in the exploration area using full-azimuth seismic data processing, spectral decomposition, AVA/AVAZ inversion and complex analysis of dynamic characteristics of the wave field in combination with well logging and core data made it possible to identify the zones of derated carbonate reservoir with changes in the characteristics of the rock skeleton, the presence void space of the porous-cavernous-fractured type and zones of lithological replacement and secondary processes, thereby reducing the risks associated with subsequent production drilling.
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P.S. Minyuk
N.A. Shilo North-East Interdisciplinary Scientific Research Institute, Far Eastern Branch of the Russian Academy of Sciences, Magadan, Russia
Keywords: Olduvai event, geochemistry, Pleistocene, Lake Elgygytgyn, orbital cycles
Abstract >>
The distribution of geochemical characteristics in the sediments of Lake Elgygytgyn (Chukotka) formed during the Olduvai event has been studied. A clear geochemical and rock magnetic zones of the section has been established, reflecting global climatic changes. The geochemical zones coincide with the marine isotope stages 75-61. Sediments of the warm stages are characterized by increased contents of mobile elements (SiO2, CaO, Na2O, K2O, Sr), high values of magnetic susceptibility, low contents of Fe2O3, MgO, TiO2, Al2O3, Rb, Zr, Ni, low values of LOI, paramagnetic component, chemical indices of alteration. The reverse pattern is observed for sediment of the cold stages. The low values of magnetic susceptibility in sediments of the optimal stages of MIS 63, 65, 71 and 75 are due to the dilution of detritus material by biogenic. The upper boundary of the Olduvai event takes place in the warm stage of MIS 63, the lower one coincides with the boundary of the stages of MIS 74 and MIS 75. The catchment for the sediments of Lake Elgygytgyn were the products of weathering of acidic Cretaceous rocks of the Pykarvaam and Ergyvaam formations, located near the lake. According to the geochemical and rock magnetic data, the cyclicity of sedimentation during the Olduvai event was established with periods of about 54, 40-43, 23 thousand years. Orbital cycles of 40-43 and 23 thousand years indicate global causes of changes in geochemical characteristics.
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T.V. Donskaya1, D.P. Gladkochub1, A.B. Kotov2, E.B. Salnikova2, E.E. Badashkova1, A.M. Mazukabzov1, V.P. Kovach2, U.S. Efremova1
1Institute of the Earths Crust, Siberian Branch of the Russian Academy of Sciences, Irkutsk, Russia
2Institute of Precambrian Geology and Geochronology, Russian Academy of Sciences, St. Petersburg, Russia
Keywords: Diorites, U-Pb age, geochemistry, Early Proterozoic, Siberian craton
Abstract >>
A detailed geological, geochronological, geochemical and isotopic study of diorites from a dyke located in the central part of the Baikal uplift of the Siberian craton was carried out. Moreover, a comparison of geochemical and isotopic data obtained for diorites of the studied intrusion with coeval mafic and intermediate igneous rocks of the southern part of the Siberian craton was carried out. The U-Pb (ID-TIMS) baddeleyite age of 18627 Ma was obtained for diorite from a dyke located in the area of the Onguren village. The obtained data is the first reliable age determination for the Early Proterozoic mafic and intermediate igneous rocks of the Baikal uplift, which are part of the South Siberian post-collisional magmatic belt. The dyke has a northeast strike. The dyke rocks correspond to diorites in chemical composition and are highly differentiated varieties (mg# = 36.537.4). There were no significant variations in the composition of diorites in the marginal and central parts of the dyke. The rocks are characterized by low contents of TiO2, P2O5,
Nb, high concentrations of Th, Zr, Ba, light rare earth elements and exhibit low
negative values εNd(t) = -5.9...-6.2. It is assumed that the source of diorites was the enriched
subcontinental lithospheric mantle. Analysis of geochemical and isotopic data
obtained for Early Proterozoic mafic and intermediate igneous rocks of the South
Siberian post-collisional magmatic belt within the Aldan
shield, the Baikal uplift and the Irkut block of the Sharyzhalgay uplift showed
that most rocks showed similar negative values of εNd(t) in range from
-4.3 to -11.6 and geochemical characteristics corresponding to rocks, the
formation of which is associated with the melting of subduction-modified
lithospheric mantle sources in a post-collisional extension environment at the
final stage of formation of the Siberian craton in the Early Proterozoic.
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Yazgul Nugumanova 1, Anna Doroshkevich 1,2, Anastasiya Starikova 1, Anton Ponomarchuk1
1V.S. Sobolev Institute of Geology and Mineralogy, Siberian Branch of the Russian Academy of Sciences Novosibirsk, Russia
2Geological Institute, Siberian Branch of the Russian Academy of Sciences Ulan-Ude, Russia
Keywords: Aillikites, 40Ar/39Ar age of phlogopite, Reverse zoning, Polyphase inclusions
Abstract >>
The paper presents data on the age and composition of phlogopite from dykes of ultramafic lamprophyres (aillikites) of the Zima complex, located within the Urik-Iya graben, Eastern Sayan region, southern margin of the Siberian craton. Samples for study were selected from post-carbonatite dykes of the Bolshaya Tagna massif, Bushkanay dyke and Southern pipe. The studied samples consist of olivine macrocrysts and fully crystallized groundmass. The groundmass consists mainly of phlogopite, perovskite, spinel and apatite group minerals, carbonates and other minerals. Phlogopite is a typical groundmass mineral in the ultramafic lamprophyres of the Zima alkaline ultramafic carbonatite complex. Phlogopite was also found in polycrystalline inclusions of olivines and in polyphase inclusions of chromites. In the studied samples, phlogopite has tabular, zoned crystals; the size and composition of the phlogopite grains vary greatly. Phlogopite is mainly represented by anticrystals, with cores composed of ferruginous high-alumina phlogopite. Phlogopite cores of the Zima complex aillikites containing Al2O3 (14-18 wt.%), FeO (7-18 wt.%), TiO2 (3-6 wt.%) were formed from early portions of a more evolved aillikite melt. Phlogopite containing Al2O3 (10-14 wt.%), FeO (4-10 wt.%), TiO2 (1-2 wt.%) was crystallized from the parental magma. The age of formation of the Bolshaya Tagna aillikites, obtained from phlogopite, is 6357 Ma (TGK 3). The age of phlogopite from the Southern pipe aillikites is 6477 Ma (BZT 4/21). The obtained ages are consistent with the age of formation of Neoproterozoic alkaline-ultramafic carbonatite complexes of the Siberian craton and other occurrences of aillikites formed as a result of extension of the Rodinia lithosphere.
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R.A. Valiullin, A.Sh. Ramazanov, R.F. Sharafutdinov, D.V. Kosmylin, F.F. Davletshin, R.Z. Akchurin
Ufa University of Science and Technology, Ufa, Russia
Keywords: active thermometry, temperature, shut-in well, behind-the-casing-flow, induction heating, casing, natural thermal convection, experimental studies
Abstract >>
The paper presents the results of experimental studies of the thermal field in the nonoperating well (without movement of liquid in the casing) in relation to the determination of the column flow upward (movement of liquid in the behind-the-casing flow from the lower to the upper formation) by the method of active thermometry. The research was carried out on a physical model of the well, which is a vertically positioned steel pipe, to which a system of copper tubes is attached from the outside, modeling the channel of the backflow. The pipe contains a local heating section, above which a temperature sonde is located to register a thermal disturbance from the heating section. The effect of natural thermal convection in a liquid on the temperature field in a pipe during and after heating is stopped has been studied. The fact of the presence of high-frequency temperature fluctuations on sensors registering the temperature of the inner surface (wall) of the pipe and liquid above the heating site has been established. The magnitude of temperature fluctuations reaches more than 2 degrees Celsius and decreases with increasing distance to the heating section. An empirical relationship has been obtained linking the arrival time of the front of the temperature disturbance associated with natural thermal convection and the distance to the heating section of the pipe. The curves of the azimuthal temperature distribution on the inner wall of the pipe above the heating section are constructed in the absence and presence of a behind-the-casing flow. Qualitative criteria have been obtained indicating the presence of azimuthally localized behind-the casing flow (sector overflow) of liquid based on the analysis of the azimuthal temperature distribution..
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A.G. Konstantinov
Trofimuk Institute of Petroleum Geology and Geophysics Sibirian Branch of the Russian Academy of Sciences, Novosibirsk, Russia
Keywords: Ammonoids, Late Anisian, paleobiogeography, Boreal Realm
Abstract >>
Identification of patterns of geographic differentiation of individual groups of marine invertebrate fauna in the geological past is important for understanding their evolutionary history, solving issues and problems of biostratigraphic subdivision and correlation of deposits. Paleobiogeographic data are also necessary to identify the stages of development of biota and the geological history of marine paleobasins and to verify paleogeodynamic reconstructions. In this work, taking into account the latest data on paleontology and biostratigraphy of the Boreal Triassic, the taxonomic composition and distribution of Upper Anisian ammonoids in various regions of the Boreal region are revised. A correlation of Upper Anisian deposits of Northeast Asia, British Columbia, Arctic Canada, Svalbard, Franz Josef Land and Khabarovsk Territory was carried out at the zonal level and a basis was obtained for a comparative analysis of coeval ammonoid faunas. As a result of a qualitative and quantitative comparative analysis of ammonoid complexes for various chrons of the Late Anisian, it was established that in the Late Anisian, British Columbia was constantly part of the Canadian province of the Boreal region, and Northeast Asia was part of the Siberian province. At the end of the Late Anisian (most of the late part of the Frechites nevadanus or Frechites chischa chrons), provincial differences were smoothed out and for the first time all Boreal regions were included in the Siberian province, with the exception of the territory of British Columbia. Analysis of the geographical distribution of some groups of ammonoids in the Late Anisian and changes in the areas of taxa over time made it possible to identify probable migration routes of Longobarditidae (genus Longobardites) and to introduce significant changes in the ideas about the centers of origin and migration of some Beyrichitidae.
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E.V. Levashova1, D.R. Zozulya2, L.N. Morozova2,3, S.G. Skublov1,4, P.A. Serov3
1Institute of Precambrian Geology and Geochronology, Russian Academy of Sciences, St. Petersburg, Russia
2 Geological Institute of the Kola Science Center, Russian Academy of Sciences, Apatity, Russia
3All-Russian Research Institute of Mineral Resources named after N.M. Fedorovsky, Moscow, Russia
4Saint Petersburg Mining University named after Empress Catherine II, Saint Petersburg, Russia
Keywords: zircon, geochemistry of trace elements, geochemistry of rare-earth elements, rare-metal pegmatites, Kolmozo deposit, Polmostundra deposit
Abstract >>
A detailed mineralogical and geochemical study (using EPMA and SIMS methods) of zircons from rare metal pegmatites of the Polmostundra and Kolmozero lithium deposits of global significance (Kola Peninsula, Arctic zone, Russia) has been conducted. The distinctive characteristics of the studied zircons are: (1) anomalously high lithium content (up to 327 ppm Li according to SIMS data); (2) high hafnium content (up to 39.21 wt.% HfO2 according to EPMA data); (3) low Zr/Hf ratios
(ranging from 0.74 to 4.70); (4) high volatile component content (up to 5.98 wt.%
water, up to 0.65 wt.% F, up to 0.12 wt.% Cl according to SIMS data); (5)
high content of trace elements, the main of which are Th, Ta, U, Nb, Ca, P. The
results obtained indicate the rare metal specificity of the composition of the
highly fractionated pegmatite melt of the Polmostundra and Kolmozero deposits,
from which the zircons crystallized, and indicate a high degree of its fluid
saturation. The extremely low values of the Zr/Hf ratio for zircons can be
explained by the combined effect of fractionation of the original granite melt
with lithium accumulation in the residual melt during the final stage of
pegmatite evolution and the role of fluids saturated with volatile elements.
Zircons crystallization occurred during the magmatic stage of pegmatite
formation, while its alteration took place during the hydrothermal stage. The
distribution of REE in zircons from the Polmostundra and Kolmozero deposits
indicates the formation of core zones of grains during the magmatic stage and
rim zones during the hydrothermal stage
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A.F. Emanov1, A.A. Emanov1,2, I.S. Novikov3, E.A. Gladyshev1, A.V. Fateev1,2, P.O. Polyansky1, E.V. Shevkunova1, R.A. Ershov1, V.V. Arapov1, A.A. Krivov4
1Altai‐Sayan Branch of Geophysical Survey of the Russian Academy of Sciences Novosibirsk, Russia
2 V.S. Sobolev Institute of Geology and Mineralogy, Siberian Branch of the Russian Academy of Sciences,Novosibirsk, Russia
3 Trofimuk Institute of Petroleum Geology and Geophysics, Siberian Branch of the Russian Academy of Sciences Novosibirsk, Russia
4 Novosibirsk Higher Military Command School of the Ministry of Defense of the Russian Federation, Novosibirsk, Russia
Keywords: Aigulak earthquake, Gorny Altai, fault structure, aftershocks
Abstract >>
Years after the Chui earthquake of 2003, geological structures adjacent to the focal area of the Chui earthquake are seismically activated. The Aigulak focal area is one of them, but energetically the most pronounced. Detailed studies have been carried out with the network of stations of the Altai seismological polygon, supplemented by temporary stations. The region was activated in the form of a local and compact structure measuring 10km×10km with focal depths from the first hundred m to 20km. The focal area is not a further activation along the same fault with the Chui earthquake, but is located on a subparallel fault in the nodal region with its branching into three faults. The seismic activation of the Aigulak focal area is not an aftershock process after a major earthquake, but is an activated structure with a dynamically changing seismic process. An intensive process has formed since the earthquake in 2012 with ML=6.1 with a gradual decrease in the number of earthquakes, and in 2019 the Aigulak earthquake with ML=5.5 occurred with a very strong aftershock process after it. The results of an area study of earthquake density in the focal zone indicate a change in the regime over time: from chaotic to self-organizing along short faults. It is suggested that the focal area has not reached the maximum level of seismic energy release.
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.N. Fomin
Trofimuk Institute of Petroleum Geology and Geophysics, Siberian Branch of the Russian Academy of Sciences, Novosibirsk, Russia
Novosibirsk State University, Novosibirsk, Russia
Keywords: Anabar-Khatanga saddle, Proterozoic and Phanerozoic deposits, catagenesis of the organic matter, petroleum potential.
Abstract >>
The degree of the organic matter (OM) maturation in Proterozoic, Paleozoic, and Mesozoic deposits in the Anabar-Khatanga saddle is determined from examination of reflectance characteristics of macerals (mainly vitrinite). Deposits of the Proterozoic are marked only by the presence of graphite inclusions of uncertain origin. In Cambrian, Devonian, and Carboniferous strata, the organic matter is transformed predominantly to apocatagenesis grades (C2-3). Approximately similarly altered OM (C1-3) is reported from the Tus-Takh Formation and Lower Kozhevnikova Formations (Lower Permian). In individual wells and areas, the degree of OM transformation is shown to be not higher than C12-C2 grades of mesocatagenesis (classification after A.E. Kontorovich). In the Upper Kozhevnikova Formation, catagenesis grades range within C11-C1 for the Upper Permian, and within C11-C32 for the Triassic. In Jurassic deposits, the organic matter has generally reached early mesocatagenesis (C11-C12 grades), and C2 grade in the deepest buried areas. In Cretaceous strata, the OM has been altered to a lesser extent, corresponding to PC3-C11, rarely to higher, grades of catagenesis. Prospects of petroleum generation may be associated with individual Permian, Triassic and Jurassic-Cretaceous sequences showing moderate level of the organic matter maturity.
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G.A. Leonova, A.E. Maltsev, L.M. Kondratyeva, V.A. Bychinsky, L.V. Miroshnichenko, S.K. Krivonogov
V.S. Sobolev Institute of Geology and Mineralogy, Siberian Branch of the Russian Academy of Sciences, Novosibirsk, Russia
Institute for Water and Environmental Problems, Far Eastern Branch of the Russian Academy of Sciences, ul. Khabarovsk, Russia
Vinogradov Institute of Geochemistry, Siberian Branch of the Russian Academy of Sciences, Irkutsk, Russia
Kyzylorda University named after Korkyt-Ata, Kyzylorda, Kazakhstan
Keywords: Geochemistry, early diagenesis, organic matter, sulfate reduction, authigenic mineral formation, pore water
Abstract >>
The chemical composition of bottom sediments and pore waters of organic-mineral sediments (sapropel) of Lake Kotokel (Eastern Baikal region) based on long drilling cores, 14.5 and 16.5 m. A reduction type of diagenesis has been established, during which destruction of organic matter occurs, transformation of the chemical composition of pore waters and the formation of authigenic minerals. Already in the uppermost intervals of sapropels, organic matter is subject to deep transformation processes and differs significantly in composition from that of bioproducers (plankton). The main role in diagenetic transformations of organic matter belongs to different physiological groups of microorganisms, primarily heterotrophic, amonifying and sulfate-reducing bacteria. During diagenesis, there is a change in the basic chemical composition of pore waters (HCO3, SO42, Cl, Ca2+, Mg2+, K+, Na+), a redistribution of trace elements (Fe, Mn, Sr, Ba, Pb, As, Co, Ni) and an increase concentrations of HCO3, NH4+, PO43, and Si, which is a consequence of the destruction of organic matter. In the process of bacterial sulfate reduction in pore waters, the concentration of SO42 decreases along the depth of the section, and in the sediment the proportion of reduced forms of sulfur increases and the isotopic composition of δ34S changes. Transformation of the chemical composition of pore waters and the activity of microorganisms leads to the formation of authigenic pyrite, rhodochrosite, and barite.
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