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Russian Geology and Geophysics

2023 year, number 3

1.
STRATIGRAPHIC DRILLING IN THE NORTHERN KARA SEA: FIRST CASE AND PRELIMINARY RESULTS

N.A. Malyshev1, V.E. Verzhbitskii1, M.V. Skaryatin2, M.D. Balagurov3, D.V. Ilyushin2, A.A. Kolyubakin2, O.A. Gubareva2, Y.A. Gatovskii4, V.G. Lakeev5, R.V. Lukashev5, A.V. Stupakova4, A.A. Suslova4, V.V. Obmetko1, D.K. Komissarov1
1Rosneft Oil Company, ul. Dubininskaya 31a, Moscow, 115054, Russia
2OOO RN-Exploration, Mozhaiskii Val 8, Moscow, 121151, Russia
3OOO Arctic Research Center, Leninskii pr. 55/1, bld. 2, Moscow, 119333, Russia
4Lomonosov Moscow State University, Leninskie Gory 1, Moscow, 119991, Russia
5National Intellectual Development, Lomonosovskii pr. 27, bld. 1, Moscow, 119192, Russia
Keywords: Stratigraphic drilling, sedimentary cover age and composition, petroleum potential, North Kara Basin, Arctic shelf

Abstract >>
Until recently, the sedimentary cover age and composition of the marginal North Kara Basin (northern part of the Kara Sea, Russian Arctic) remained uncertain because of the absence of direct data from parametric and exploration wells. Taking into consideration the absolute importance of these issues for understanding the regional geology of the Arctic shelf and evaluating its petroleum potential, Rosneft Oil Company, together with AO RosGeo, drilled ten shallow stratigraphic wells in fall 2020 using the research vessel (RV) Bavenit to reveal the complete stratigraphic range of the North Kara Basin. The ultrahigh-resolution (UHR) seismic survey was carried out by the RV Kapitan Voronin to adjust the well site locations and integrate the well sections into the regional geological model based on 2D seismic data during the drilling campaign. As a result, 300 m core was recovered from 11 Paleozoic and two Mesozoic stratigraphic units, previously investigated by 2D seismic and outcrop studies of the Severnaya Zemlya Archipelago. Lab analyses (biostratigraphy, lithology, sedimentology, geochemistry, and other types of core analysis) were performed at Lomonosov Moscow State University. We present obtained lab results confirming that the main part of the North Kara Basin section belongs to the Paleozoic; late Cambrian-Late Devonian rock ages have been derived. Several Paleozoic units tend to be older than those in previously published models. Core samples include mainly terrigenous rocks with insignificant carbonate presence. Paleozoic units are overlain by a thin Mesozoic terrigenous section dated from Middle Triassic to Middle Jurassic above a distinct angular unconformity. After a thorough analysis of all the lab results, we will obtain data on the ages of sedimentary units, as well as their lithology and depositional environments, and establish elements of the hydrocarbon system (source rocks, reservoirs, and seals) to evaluate the North Kara Basin petroleum potential with lesser uncertainty. We suppose that our results will significantly contribute to establishing a stratigraphic framework, reconstructing the basin history, and evaluating the petroleum potential of the whole Arctic region.



2.
LITHOLOGY OF THE UPPER TRIASSIC SEDIMENTARY ROCKS OF CHUKOTKA AND WRANGEL ISLAND AND THEIR RELATIONSHIP WITH COEVAL ROCKS OF THE EASTERN ARCTIC

M.I. Tuchkova1, S.D. Sokolov1, A.V. Moiseev1, V.E. Verzhbitskii2, V.V. Kostyleva1, E.V. Vatrushkina1
1Geological Institute, Russian Academy of Sciences, Pyzhevskii per. 7, Moscow, 119017, Russia
2Rosneft Oil Company, Sofiiskaya nab. 26/1, Moscow, 117997, Russia
Keywords: Upper Triassic, sedimentology, petrography, heavy minerals, geochemical analysis, provenance, correlation, paleoreconstruction, Chukotka, Wrangel Island

Abstract >>
The correlation between the sedimentologic characteristics of the Upper Triassic deposits of Wrangel Island and the Chukchi Peninsula (Chukotka) is discussed. These deposits are similar in isotopic, petrographic, and geochemical features. It has been established that the Upper Triassic sand strata accumulated at different sites of a single sedimentary basin, in shallow-water prodeltas of Wrangel Island and in deeper-water environments of Chukotka. In the latest Triassic, the portion of the sand component in the sections increased. At the same time, the average size of the sand grains decreased, which indicates weakening of the tectonic factor in some zones of the provenance and its general peneplanation with the formation of a weathering crust. The eroded complexes are composed of granitoid, metamorphic, and metavolcanic rocks. They stayed on land for a long time, being subjected to chemical weathering. The depth intervals with the large amount of sandy material in the section of Wrangel Island and Chukotka are correlated with those in the sections of the Sverdrup Basin and the northern slope of Alaska.



3.
REEF COMPLEXES OF THE LATE ORDOVICIAN--EARLY SILURIAN ALTAI BASIN: CLASSIFICATION, STRUCTURE, PALEOBIOTA, AND PALEOGEOGRAPHY

N.V. Sennikov, O.T. Obut, R.A. Khabibulina, V.A. Luchinina, E.V. Lykova, D.A. Tokarev, T.A. Shcherbanenko
Trofimuk Institute of Petroleum Geology and Geophysics, Siberian Branch of the Russian Academy of Sciences, pr. Akademika Koptyuga 3, Novosibirsk, 630090, Russia
Keywords: Reef, Late Ordovician, Silurian, Telychian, Sheinwoodian, Altai

Abstract >>
The paper presents data on the classification, structure, and biota of reef complexes from the Late Ordovician--early Silurian Altai Basin. The early Paleozoic history of the Altai Basin included the early--middle Katian, late Katian, early Hirnantian, late Telychian, and middle--late Sheinwoodian events of large-scale reef formation which produced framework reefs, mud mounds, and coral meadows. The early Paleozoic reefs of the area formed at rates of 40 to ~12 cm per thousand years. The late Telychian reef system, which formed in 0.5-1.0 Myr, occupied the largest area of the basin. The lateral extent of reef systems in the Late Ordovician-early Silurian basin of Altai depended more on the rates of vertical and lateral growth, as well as on the previous sea bottom topography and clastic inputs, than on the duration of reef formation. Carbonate deposition in the Altai basins of that time can be simulated with a general model implying formation of distal barrier reefs.



4.
ORGANIC MATTER AND GENERATION POTENTIAL OF PALEOZOIC DEPOSITS IN THE TAL'BEI BLOCK OF THE CHERNYSHEV RIDGE (Timan-Pechora petroleum province)

O.S. Kotik, I.S. Kotik, I.I. Dan'shchikova, L.V. Sokolova
Institute of Geology of Komi Science Center, Ural Branch of the Russian Academy of Sciences, ul. Pervomaiskaya 54, Syktyvkar, 167982, Russia
Keywords: Organic matter, hydrocarbons, petroleum source rocks, catagenesis, Paleozoic, Chernyshev Ridge, Timan-Pechora petroleum province

Abstract >>
The study area is located within the Chernyshev Ridge, a fold-thrust structure, which is a promising area for oil and gas exploration in the Timan-Pechora province. Petroleum source rocks of Paleozoic (from Upper Ordovician to Lower Carboniferous) deposits stripped by the Vorgamusyur-1 well in the Talbei block of the Chernyshev Ridge were studied by lithological, petrographic, organic-petrology, and organic-geochemistry methods. Most of the section is characterized by low values of Corg (<0.5%), genetic potential (S1 + S2 < 0.5 mg HC/g rock), and hydrogen index (HI < 100 mg HC/g Corg). Petroleum source rocks with elevated values of Corg (up to 0.9%), S1 + S2 (up to 2.1 mg HC/g rock), and HI (up to 277 mg HC/g Corg) were identified at different stratigraphic levels of the section: Upper Devonian (D3tm-sr), Upper Silurian (S2gj), and Upper Ordovician (O3mt). The maceral composition of organic matter (OM) and the distribution of hydrocarbons in the saturated fraction of bitumens indicate that petroleum source rocks include only marine OM (type II kerogen). The catagenetic transformation of OM was assessed based on the bituminite reflection (RVeq), Rock-Eval pyrolysis temperature (Tmax), and conodont color alteration index (CAI). The available RVeq (0.63-0.84%), Tmax (430-443 °C), and CAI (1.5-2.0) data indicate that the entire Paleozoic well section is in the oil window (MC1-MC3). The new data refined the catagenetic zonality of the sedimentary section, according to which the OM reached the following gradations: MC1 in the lower Carboniferous and Famennian deposits, MC2 in the interval from the Frasnian to the upper part of the Lower Silurian, and MC3 in the Lower part of the lower Silurian and in the Upper Ordovician. The results of a study of petroleum source rocks and the type and maturity of OM will be the basis for basin modeling, which will increase the reliability of reconstructions of oil and gas formation at the Chernyshev Ridge.



5.
THE KATAEVO ISLAND ARC SYSTEM OF THE PALEOASIAN OCEAN (Transbaikalia): COMPOSITION, AGE, PALEOMAGNETISM, AND FORMATION GEODYNAMIC SETTINGS

I.V. Gordienko1, D.V. Metelkin2,3, V.S. Lantseva1, A.L. Elbaev1
1Dobretsov Geological Institute, Siberian Branch of the Russian Academy of Sciences, ul. Sakhyanovoi 6a, Ulan-Ude, 670047, Russia
2Novosibirsk State University, ul. Pirogova 1, Novosibirsk, 630090, Russia
3Trofimuk Institute of Petroleum Geology and Geophysics, Siberian Branch of the Russian Academy of Sciences, pr. Akademika Koptyuga 3, Novosibirsk, 630090, Russia
Keywords: Kataevo volcanic arc, Neoproterozoic, geochemistry, U-Pb age, paleomagnetism, Paleoasian Ocean, Siberian paleocontinent

Abstract >>
Based on new data on the geology, composition, U-Pb isotopic age, and paleomagnetism of the metavolcanic rocks of the Kataevo Formation, we consider the geodynamic conditions of their formation and alteration. The Kataevo Formation metavolcanic rocks belong to the K-Na-high-alumina andesite-andesibasalt-basalt volcanic series. Results for U-Pb analysis of magmatic zircon (SHRIMP II, 8 spots) from a metaandesibasalt sample of the stratotype section on Ungo R. yielded and age of 852 ± 9 Ma. Isotope systems for Sm-Nd yield a positive εNd(852) = + 9.29, which indicates a juvenile magmatic source, close to depleted mantle (DM), with a Neoproterozoic protolith TNd(DM) model age. The content of the less mobile HFSE and REE (ppm) is consistently low for Nb (8-15), Ti (7074-12,410), Ta (0.32-0.93), Eu (1.80-2.29), Ñå (50-79), Y (21-25), Yb (2.1-2.8), Rb (10-24) and elevated for Sr (1000-1500), Zr (170-270), La (25-41), and Ba (600-800). All studied parameters place the metavolcanic rocks close to the contemporary Kurile-Kamchatka type of developed island arcs. Paleomagnetic analysis of the section of metavolcanic rocks shows a complete remagnetization ca . 120 Ma. This is synchronous with manifestations of intraplate basaltoid magmatism in the studied region, the most typical example of which is the Lower Cretaceous Khilok Formation.



6.
THE MAL'DZHANGARKA CARBONATITE MASSIF (Anabar Shield): THE AGE OF MAGMATISM AND MINERALIZATION (U-Pb and Re-Os isotope systems)

A.V. Molchanov, V.E. Guzev, E.N. Lepekhina, R.Sh. Krymskiiy, A.V. Antonov, B.V. Belyatsky, E.I. Khorokhorina
A.P. Karpinsky Russian Geological Research Institute, Srednii pr. 74, St. Petersburg, 199106, Russia
Keywords: Carbonatite, U-Pb age, zircon, pyrochlore, Re-Os isotope dating, Mal’dzhangarka massif, Anabar Shield

Abstract >>
We present the first results of a comprehensive isotope-geochemical study of dolomitic carbonatites of the Mal’dzhangarka massif located in the southeast of the Billyakh melange zone (southeastern periphery of the Anabar Shield). Zircon grains separated from core samples from a depth of 6-30 m have a three-phase structure. All of them were trapped from the host metamorphic rocks and mark the age of the main stage of high-gradient metamorphism in the region, 2027 ± 9 Ma. Pyrochlore containing 38-705 ppm U and 5-21 ppm radiogenic Pb, with weak metamictization of the crystal lattice and an undisturbed U-Pb system, made it possible to estimate the concordant age of rare-metal mineralization in the massif, 167 ± 4 Ma, which is probably close to the crystallization age of the host carbonatites. The estimated age corresponds to one of the stages of kimberlite-carbonatite magmatism on the eastern slope of the Anabar dome. The Rh-Os isotope system of pyrite from superposed late carbonate-sulfide veinlets in the carbonatites testifies to a close (within the error of determination) age, 179 ± 14 Ma, and a low initial Os isotope ratio, which indicates the contribution of mantle material to the formation of this isotope system.



7.
ANALYSIS OF TRANSIENT CHARACTERISTICS OF INDUCED POLARIZATION IN INNOVATIVE MINERAL EXPLORATION SOLUTIONS (from case studies of gold deposits)

G.V. Gurin1,2, A.V. Tarasov1,2, K.V. Titov2
1Rudgeofizika, ul. Aerodromnaya 8A, St. Petersburg, 197110, Russia
2St. Petersburg State University, Universitetskaya nab. 7/9, St. Petersburg, 199034, Russia
Keywords: Spectral induced polarization, relaxation time, chargeability, gold deposits

Abstract >>
The paper discusses current state of the spectral approach to analysis of induced polarization (IP), its possibilities and limitations, along with directions for the method development. Reviewed are the main methods and approaches for estimation of spectral IP parameters and their specific features. Our practical experiments have shown the advantages of analysis of transient IP characteristics over standard approaches to the IP data analysis and processing. Results of the standard and spectral approaches application to analysis of IP data when solving mineral exploration problems at the Maletoyvayam gold deposit (Kamchatka Peninsula) and the Yasnoe gold occurrence (Taimyr Peninsula) are compared. Here, we demonstrate that low efficiency of works is erroneously regarded as one of the main factors hindering a broad adoption of the spectral IP method in mineral exploration activities. Rather, it is a lack of automated techniques for analysis of transient IP characteristics. We propose a new approach to spectral analysis of IP data, based on the algorithms for image recognition of a reference object, and describe pioneering efforts of its practical application.



8.
BUILDING OF THERMOPHYSICAL ROCK PROPERTIES FROM ELECTROMAGNETIC SOUNDING DATA AND LABORATORY MEASUREMENTS

V.V. Spichak, A.G. Goidina, O.K. Zakharova
Geoelectromagnetic Research Centre of the Schmidt Institute of Physics of the Earth, Russian Academy of Sciences, Troitsk, Moskovskaya obl., 108840, Russia
Keywords: Thermal conductivity, heat flow, specific heat capacity, magnetotelluric sounding, geothermal reservoir, artificial neural network

Abstract >>
Possibilities to construct the sections of thermal conductivity, specific heat capacity, as well as heat flow density at the surface, using electromagnetic sounding data and laboratory measurements on core samples, have been studied. It has been shown that neural network prediction of thermophysical properties from electromagnetic sounding data and laboratory measurements enables estimating these properties not only below boreholes but also in the interwell space, with relative accuracy around 6-10 %. Sections of «dry» and «warm» thermal conductivity, specific heat capacity and a profile of the heat flow density at the surface of the study area, along magnetotelluric sounding profile, have been built.



9.
PREDICTING DYNAMIC EFFECTS OF LARGE EARTHQUAKES IN AREAS OF DEGRADING PERMAFROST (Baikal-mongolia region)

V.I. Dzhurik1, E.V. Bryzhak1, Ts. Batsayhan2, S.P. Serebrennikov1
1Institute of the Earth's Crust, Siberian Branch of the Russian Academy of Sciences, ul. Lermontova 128, Irkutsk, 664033, Russia
2Institute of Astronomy and Geophysics, Mongolian Academy of Sciences, District 15, Ulaanbaatar, Mongolia
Keywords: Seismicity, permafrost, dynamic effect, seismogram, frequency response, Burenhan mining and processing works, Ìóya basin, Baikal-Mongolia region

Abstract >>
The study addresses basic problems of modern geodynamics and seismicity of the Central Asian lithosphere. It aims at predicting dynamic effects of large earthquakes for seismic safety of the Baikal-Mongolian region. Special focus is made on the seismic behavior of areas where seismic risk zoning is problematic because of permafrost. The paper presents synthesis of previous and new data on ground responses to large earthquakes in specific territories of the Baikal-Mongolia region with complex cryological conditions. The results include shaking intensity patterns and predicted seismic parameter values for degraded permafrost in zones of different climates and seismicity levels. The obtained prediction maps can make reference in studies of variable permafrost responses to temperature, seismic, and mining-related impacts.