1Geological Institute, Russian Academy of Sciences, Moscow, Russia 2Shirshov Institute of Oceanology, Russian Academy of Sciences, Moscow, Russia 3Moscow Institute of Physics and Technology, Dolgoprudny, Russia 4Trofimuk Institute of Petroleum Geology and Geophysics, Siberian Branch, Russian Academy of Sciences, Novosibirsk, pr. Akademika Koptyuga 3, Russia 5Novosibirsk State University, Novosibirsk, Russia 6VNIIOkeangeologia, St. Petersburg, Russia 7Polar Geophysical Institute, Murmansk, Russia 8Schmidt Institute of Physics of the Earth, Russian Academy of Sciences, Moscow, Russia
We provide a brief description of the main structures in the Eastern Arctic, in the evolution of which two major stages have been distinguished and considered: the late Paleozoic–early Mesozoic and the Late Jurassic–Early Cretaceous. We have established the synchronicity of tectonic events on the Arctic margins of Northeast Asia and Arctic Alaska and within the structures of the Amerasia Basin, indicating the existence of a cause-and-effect relation between the compression (fold-and-thrust structures) and extension (rifting and spreading in the Canada Basin). We have proposed the tectonic models of the formation of fold-and-thrust structures in Chukotka and Arctic Alaska and have determined their similarities and differences. Paleotectonic reconstructions have been performed for 160 and 120 Ma. We present a critical review of the concepts about the formation of the structures in the Amerasia Basin and provide a subduction-convection geodynamic model according to the analysis of seismic tomography of the mantle and regional geology and tectonics data. This model was previously used to describe the Cretaceous and Cenozoic evolution of the Arctic lithosphere at a qualitative level. The model is based on the idea of the existence of a two-tier subduction system: a horizontally extended convection cell in the upper mantle, coupled with a conveyor mechanism of subduction of the Pacific lithosphere. As a result, there is a convergence of the “outer” Pacific subduction zone and the “inner” subduction zone located inside the South Anyui and Angayucham oceanic basins, which provides their closure and subsequent collision. Under the influence of the reverse upper mantle flow, scattered deformations of the Amerasia lithosphere occur, caused by viscous dragging with flows beneath the lithosphere, which is the reason for the diversity of the structures in the Amerasia Basin and the Canada Basin in particular. In addition, the developed geodynamic model is supplemented by a tectonic and magmatic mechanism of crustal subsidence and the formation of sedimentary basins.
A.Sh. Shavekina1, V.A. Danilovsky1, O.L. Gaskova1, Yu.A. Kalinin1, R.V. Kuzhuget2 1 V.S. Sobolev Institute of Geology and Mineralogy, Siberian Branch of the Russian Academy of Sciences,Novosibirsk, Russia 2 Tuvinian Institute for Exploration of Natural Resources, Siberian Branch of the Russian Academy of Sciences, Kyzyl, Russia
Keywords: Ag, silver, oxidation zone, halides, chalcogenides, supergene processes, Kyzyk-Chadr deposit, thermodynamic modeling.
The behavior of silver (Ag) in the oxidation zone of the Kyzyk-Chadr gold-sulfide-quartz deposit (Tuva Republic, Russia) has been studied. The main focus was on the mechanisms of Ag differentiation under supergene conditions, including the formation of its secondary minerals and its incorporation as an isomorphic impurity into other phases. It was found that Ag in the oxidation zone forms chalcogenides (acanthite, petrovskaite, uytenbogaardtite, jalpaite) and halides (iodargyrite, bromargyrite, mayersite), which are associated with malachite, chrysocolla, brochantite, quartz, and iron hydroxides. Electron probe microanalysis (EPMA) revealed that Ag concentrates in secondary copper sulfides (covellite, chalcocite, yarrowite, etc.), with levels as high as 0.7 wt.%. Optimization of EPMA parameters to improve resolution lowered the detection limit, enabling the determination of low Ag contents in chalcopyrite (up to 0.05 wt.%) and bornite (up to 0.09 wt.%). The sources of Ag are primary Ag tellurides and selenides, as well as primary and secondary Cu sulfides that break down during oxidation. Thermodynamic modeling simulated the behavior of Fe, Cu, and Ag during progressive oxidation of the primary assemblages (bornite, chalcopyrite, acanthite). The Eh-pH conditions controlling mineral migration and reprecipitation were calculated, and the element concentrations necessary for the formation of secondary phases were estimated.
The paper reviews the results of comprehensive studies and dating of contourite deposits from the Southwest Atlantic. It focuses on sediment transport and depositional processes as well as sediment sources in the context of Pliocene-Quaternary environmental and climatic changes. The work primarily highlights investigations conducted over the past decade by the Laboratory of Paleoceanology of the Shirshov Institute of Oceanology RAS in collaboration with other research groups over the last decade. The study examines contourite systems along the Argentine Patagonian continental slope, on the Santa Catarina and São Paulo plateaus, the Ioffe contourite Drift and the gravitite-contourite system, at the foot of the São Tomé Seamount . These systems were identified using a comprehensive approach combining seismo-acoustic, lithological, geochemical, and magnetic susceptibility data. Specific features of contourites that distinguish them from other types of deep-sea sediments are considered. The sediment age was defined by biostratigraphy and/or oxygen isotope stratigraphy and confirmed by AMS-14C dates (within the last 50 ka). The depositional system formation was predominantly controlled by erosion-depositional activity of bottom along-slope currents of the Antarctic origin. These Antarctic waters are a key component of Atlantic meridional circulation and the global conveyor system. Consequently, the contourite systems formed under the influence of these waters preserve a geological archive of the region's climatic and oceanographic history. The Ioffe Drift contains the longest sedimentary record in the study area, spanning the last 3.2 Ma. This time interval captures the development of modern-type paleoceanographic variability following the closure of the Panama Gateway. Other studied systems preserve sedimentary sequences documenting glacial-interglacial stages and associated changes in sea level, climate, and bottom current circulation during the Late Quaternary.
Merkulov O.I., Afanasenko A.P., Moskovsky I.G., Glukhova E.V. 1. JSC «Rosgeology», Moscow, Russia
2. JSC «Nizhne-Volzhsky Scientific Research Institute of Geology and Geophysics», Saratov, Russia
Keywords: hydrocarbons, hydrocarbon system modeling, geochemistry, hydrocarbon generation, compositional kinetic spectra, oil and gas source rocks, hydrocarbon potential, chromatography, pyrolysis
This article presents the fundamental principles of the author's technology for the justification and reconstruction of compositional kinetic spectra GeoArrhenius/SpectrOptim. The advantage of this technology lies in its ability to confidently separate gaseous hydrocarbons on the chromatogram and reconstruct multi-component (with an arbitrary number of components) kinetic spectra at the onset of catagenesis based on neural network modeling. Utilizing this technology in modeling hydrocarbon systems allows for accurate assessments of the volumes of hydrocarbons generated by the oil and gas source rock, and consequently, enables the evaluation of hydrocarbon resources in the area of study. This approach reduces the reliance on external and internal analogs during calculations, as well as the expert opinions of geological researchers.
U.A. Moroz1, A.V. Nikiforov1, V.V. Yarmolyuk1,2, A.M. Kozlovsky1, A.A. Ivanova3, E.V. Salnikova3, V.M. Savatenkov3, U.V. Plotkina3, А.К. Khertek2, N.A. Polyakov1 1 Institute of Geology and Ore Deposits, Petrography, Mineralogy and Geochemistry, Russian Academy of Sciences, Russia 2 Tuvinian Institute for Exploration of Natural Resources of Siberian Branch of the Russian Academy of Sciences, Kyzyl, Russia 3 Institute of Precambrian Geology and Geochronology, Russian Academy of Sciences, St. Petersburg, Russia
Keywords: nepheline syenites, Central Asian Orogenic Belt, magma differentiation, isotopic composition, geochronology, Sangilen, rare-metal magmatism.
Massifs of alkaline granitoids and nepheline syenites are quite widespread in the territory of Eastern Tuva. Rare metal deposits and ore occurrences, which were formed mainly at the end of the Carboniferous period and in the Permian, are often associated with them. The Naryn massif includes nepheline syenites of the main phase, contact zone and a complex of 3 types of foidite microsyenite dikes. The age of the massif determined by zircon from the rocks of the main phase (SIMS – 315±3 million years) and dikes of microsyenites-1 (CA ID TIMS – 318±1 million years) showed an earlier time of its formation in the middle of the Carboniferous. Mineralogical, geochemical and Nd-isotope characteristics of the massif rocks suggest that the diversity of its rocks is associated with the same type of differentiation of a single initial magma, but occurring at different hypsometric levels. Crystallization of biotite-pyroxene-amphibole nepheline syenites of the main phase and feldspar liebnerite syenites of the marginal zone occurred at the upper level. From the lower chamber with the differentiating melt, dykes of apo-amphibole nepheline microsyenites-1, pyroxene-biotite microsyenites-2 and biotite nepheline microsyenites-3 were successively intruded. The evolution of melts, both at the upper and lower levels, occurred due to the precipitation of mafic minerals (amphibole), apatite and feldspar. With an increase in the alkalinity of the melts, accumulation of rare elements (Zr, Nb, Ta, REE) occurred, which are included in their own minerals at the late stages of rock crystallization. These data indicate that the foidite series rocks, widespread in Eastern Tuva, may be potentially ore-bearing, and the middle of the Carboniferous period should be considered as a phase of alkaline magmatism of the East Sayan rare-metal metallogenic zone. The Nd isotopic composition of the Naryn massif rocks (Nd(T) +6.3 – +7.1) does not suggest significant participation of the continental crust in the source of melts, therefore, sublithospheric alkaline-basaltoid magmas probably served as parental rocks for all the Naryn massif rocks.
Using a model sample of pyrite ore collected at the Degdekan gold deposit (North East Russia), we demonstrate the use of different variants of the IСP-MS method to determine the ratio of surficial-bound and structural-bound forms of trace elements (TE) in pyrite. Despite the difference in the physicochemical nature of the analysis methods involving the decomposition of crystals of different sizes (analytical data selections for single crystals - ADSSC) and direct determination by scanning the surface with a laser beam of different power (LA-IСP-MS), it has been shown that a number of elements tend to enrich the surface layer of pyrite crystals. The ratio of TE contents in the surface layer and in the volume (structure) of the crystal is defined as the selectivity (S) of surficial phases in the uptake of a given element. According to ICP MS – ADSSC data, the selectivity was 3.9 (Mn), 3.3 (Ag), 6.4 (Pd), 6.4 (La), 0.3 (Pr), 0.8 (Tb), 2.6 (Ho), 0.5 (Er), 1.0 (Lu), according to the results of LA-ICP-MS 3.9 (Mn), 1.4 (Co), 6.2 (Ni), 1.6 (Cu), 0.9 (Sb), 0.2 (Au), 0.3 (As), 6.8 (Ag), 18 (La), 46 (Ce), 5.2 (Pr), 11 (Nd), 1 (Eu), 0.6 (Dy). A comparison with experimental data for S Mn, Pd, and Ag reveals comparable results. However, it is concluded that LA-IСP-MS should be more representative in order to enable criterion-based statistical sampling (CBSS) according to a principle similar to ADSSC for more accurate discrimination of the structural component of TE concentration. Otherwise, significant errors are possible due to the influence of microinclusions of autonomous phases, in this case galena, which concentrates As, Au and Sb due to heterovalent isomorphism, resulting in S<1 for these elements. Most of the studied TEs show a direct correlation between selectivity and the difference in the ionic radii of the element and Fe, which confirms the relationship between S and the level of incompatibility of the impurity element in FeS2. High correlation coefficients between light REEs in the surface and the absence or negative correlations between light and heavy REEs are noted. This may reflect differences in the species of heavy and light lanthanides and requires more detailed study using LA-ICP-MS surface analysis and the application of the CBSS procedure. Despite the preliminary nature of the results, they deserve attention in practical terms as a justification for the development of technology for the extraction of critically important REEs as by-products in the processing and enrichment of pyrite ores and concentrates. They also justify the importance of the surface accumulation effect of REEs and the need to take it into account in meta-analysis and statistical processing of the results of analytical determinations of element content.
This paper describes a system for monitoring seismicity in specific volcanic areas of Kamchatka (Russia, Kamchatka Peninsula) based on estimates of the seismicity level according to the SESL’09 (Statistical Estimation of Seismicity Level) methodology. The application of the SESL’09 method to studying the preparation of volcanic activations is a promising approach for monitoring volcano state. We present the results of identifying seismically active source volumes for 10 active Kamchatka volcanoes. Nomograms were constructed for these volumes, allowing for the estimation of the seismicity level for any given time interval based on the seismic energy released within it. Examples of variations in the seismicity level of the volcanic areas, which are associated with the preparation for an eruption, are provided and support this conclusion.
A.V. Degterev¹, S.Z. Smirnov², D.V. Kuzmin², T.Yu. Timina², A.Ya. Shevko², I.R. Nizametdinov², F.A. Romanyuk¹, M.V. Chibisova¹ 1Institute of Marine Geology and Geophysics, Far Eastern Branch of the Russian Academy of Sciences, Yuzhno-Sakhalinsk, Russia
2V.S. Sobolev Institute of Geology and Mineralogy, Siberian Branch of the Russian Academy of Sciences, Novosibirsk, Russia
Keywords: Kuril Islands, Iturup Island, caldera, Lvinaya Past, pyroclastic deposits, explosive eruptions, pyroclastic flows, tephra, radiocarbon dating, geochemistry
At the end of the Pleistocene, two large-scale volcanic eruptions, associated with the formation of the Lvinaya Past caldera, occurred in the southern part of Iturup Island (Southern Kurils). These eruptions resulted in the formation of the largest partially submerged caldera in the Kuril Island arc, measuring 7×9 km, with a rim area of ~50 km² and a volume of ~25 km³ (including a submarine part of 12.26 km³). Comprehensive geological and geochronological studies established that the caldera formation was associated with two successive, very powerful explosive eruptions (LP-I and LP-II), separated by a repose period of several hundred years. The age of the first eruption (LP-I) is likely about 13,500 cal yr BP. The age of the second eruption (LP-II), determined from a series of radiocarbon dates, is estimated at ~12,300 cal yr BP. The eruptions were of Plinian type and involved the massive ejection of silicic pyroclastic material, represented by pyroclastic flow deposits and tephra. Based on silica and total alkali contents, the pumice from the caldera-forming eruption corresponds to low-alkali dacites and rhyodacites (SiO₂ 63.4–69.95 wt.%, total alkalis 3.9–5.5 wt.%), with less frequent andesitic (SiO₂ 58.3 wt.%, total alkalis 3 wt.%) and rhyolitic compositions (SiO₂ ~74 wt.%, total alkalis 5.6 wt.%). The total volume of erupted material from both events is preliminarily estimated at 80–100 km³ (DRE 35–45 km³), with the LP-II eruption being 30–40% more powerful than LP-I. It is suggested that the LP-I and LP-II eruptions, occurring only a few hundred years apart, could have impacted the natural environment on a regional and possibly global scale.
When conducting seismic surveys on the ground, it is usually not possible to place receivers with a uniform sufficiently frequent step over the area of observation. Interpolation (regularization) is an effective tool for generating additional seismic records without changing the spectral composition of data over time and with expansion of the spectral composition over space. This paper considers the optimization of a regularization algorithm based on iterative application of discrete Fourier transform (DPF) over a space known as ALFT (Anti-leakage Fourier transform). The proposed modification of ALFT is a way to reduce the set of test wave numbers when performing DPF. The effectiveness of the proposed algorithm was confirmed by processing both synthetic and field data. The calculation time has been reduced by several times compared to the original algorithm, and the results of recovery of skipped routes have not deteriorated. The results are valuable from a practical point of view and can be applied in future to the processing of ground-based seismic data on an industrial scale.
N.A. Mukhortina, E. V. Zippa 1Tomsk Branch of Trofimuk Institute of Petroleum Geology and Geophysics of Siberian Branch Russian Academy of Sciences, Tomsk, Russia
Keywords: polycyclic aromatic hydrocarbons, thermal waters, genesis of PAHs, technogenic load, water-rock system
New data on the composition and distribution of polycyclic aromatic hydrocarbons (PAHС) in thermal waters and host rocks in Baikal Rift Zone were obtained. It was shown that the total content of all identified individual compounds is 0.17-1.15 μg/L in the thermal springs and is 0.021-1.19 μg/kg in the rock. Naphthalene, phenanthrene, and dibenzo[a,h]anthracene dominate in the water. Phenanthrene, fluoranthene, and dibenzo[a,h]anthracene are predominant in the rock. The total PAHC content increased with TDS of water and with N2 and He growth in escaped gases. The calculated coefficients of technogenic load showed a low level of pollution for all studied sources. According to indicator ratios, the PAHC origin was determined. On the one hand, PAHC in thermal waters had petrogenic origin and were formed due to geochemical transformations of organic matter under high temperatures and pressures and microbial activity, entered with aqueous and gas along faults and fractures. On the other hand, some compounds have a natural pyrogenic origin, where pyrolysis products enter springs either at near-surface conditions or when mixing. The results let to characterize the composition of thermal waters in more detail and to describe a conceptual model the thermal waters composition formation in the studied region.
D.A. Ilyin1, I.V. Korovnikov 1,2 1Trofimuk Institute of Petroleum Geology and Geophysics, Siberian Branch of the Russian Academy of Sciences, Novosibirsk, Russia
2 Novosibirsk State University, Novosibirsk, Russia
Keywords: Rhynchonelliformea brachiopods, Siberian platform, Cambrian, facies occurrece, paleogeographic distribution.
The article analyzes the published data and collections of brachiopods available to the authors for the systematic composition of brachiopods of the Rhynchonelliformea from the Cambrian of the Siberian platform. Currently, 50 species have been described and one taxon has been assigned to the genus (Finkelnburgia sp.). All of them belong to 15 genera, 10 families (two genera have not been identified as belonging to families), and five classes. Cambrian brachiopods of the Rhynchonelliformea of the Siberian Platform are divided into six associations, which are characterized by a certain taxonomic composition, paleogeographic and stratigraphic distribution. The most representative are brachiopods of the Obolellata. Their findings were noted in North America and Greenland and allow us to compare the deposits of the Lower Cambrian of North America and the Siberian platform quite confidently. The Strophomenata is also widely used. But of the ten Siberian species of the Billingsella genus, eight are endemic. Therefore, the findings of these brachiopods can be effectively used for correlation at the generic level to compare the transitional layers between the Middle and Upper Cambrian. Representatives of other classes (Chileata, Kutorginata, and Rhynchonellata) have less potential for inter-regional correlations. Although some of their representatives are found in other regions of the world and can be used as an additional tool for comparing remote sections.
A.P. Afanasenkov1, I.S. Gribova1, 2, V.V. Narkisova2, I.V. Neronova2 1Joint Stock Company "Rosgeologiya", Moscow, Russia 2Joint-Stock Company «Scientific and Production Center for Ultra-Deep Drilling and Integrated Study of the Earth's Interior», Yaroslavl, Russia
Keywords: wend, Pre-Yenisei sedimentary basin, geophysical correlation of well sections, lithology, potential reservoirs of oil and gas accumulation.
The Severo-Ketskaya parametric well was drilled by JSC NPC Nedra to a depth of 5,200 m in the period 2021-2023. The well is located in the south-west of the Pre-Yenisei sedimentary basin in the dome zone of the large anticlinal structure of the same name, buried under the Meso-Cenozoic cover. The well uncovered a new carbonate-terrigenous section of the Vendian and carbonate deposits, presumably of Ripheanage, for the Pre-Yenisei sedimentary basin. The article substantiates the stratigraphic boundaries of the Vendian on the basis of geophysical correlations with typical sections of the southwest Siberian Platform, presents the general lithological characteristics of the Vendian section and the exposed part of the Riphean (?). According to the data of the primary core study, the results of geophysical studies and tests of objects, the deposits of the Upper and Middle Danilovskoye subhorizonts are the most promising for oil and gas accumulation in the Vendian complex of rocks in the borehole drilling area. The results of geochemicalstudies of sections of parametricwells do notallow us to associatehigh oil and gas potentialwith the Proterozoic deposits of the Pre-Yenisei sedimentarybasin
M.A. Krainov 1,2, E.V. Bezrukova 1, A.Yu. Kazansky 2,3, A.A. Shchetnikov 1,2 1Vinogradov Institute of Geochemistry SB RAS, Irkutsk,Russia
2The Institute of the Earth’s Crust SB RAS, Irkutsk, Russia
3Geological Institute RAS, Moscow, Russia
Keywords: Cis-Baikal region, Angarskaya Steppe, Late Holocene, petromagnetism, stratigraphy, lacustrine sedimentation conditions, climate, anthropogenic influence
The first reconstruction of lacustrine sedimentation conditions for the extensive territory of the Angara steppe (Pre-Baikal Depression) in the Late Holocene with decadal temporal resolution is presented. The reconstruction is based on the results of a comprehensive study of Lake Ordynskoe sediments: petromagnetic and granulometric parameters, biogenic silica content. Sedimentation rates and the age of the reconstructed events were determined using radioisotope dating (²¹⁰Pb and ¹³⁷Cs). The age of the core base is 2800 cal yr BP. As a result, it is shown that the primary contribution to the magnetization of Lake Ordynskoe sediments, unlike other studied lakes in the region, comes from grains produced by magnetotactic bacteria. Nevertheless, the analysis of the behavior of biogenic magnetization components provided information on the Lake bioproductivity and relative changes in redox conditions during sediment formation at the water-bottom interface, while the results of granulometry were informative for reconstructing relative changes in lake level. Despite this specific feature of the formation of the lake sediment's petromagnetic characteristics, it was established that noticeable anthropogenic influence on the Lake Ordynskoe geosystem began approximately 280 years ago, intensifying significantly in the last century due to the agricultural activity.
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