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.
V.S. Zykin1,2, V.S. Zykina1, R.N. Kurbanov3,4, A.O. Volvakh1, N.E. Volvakh1, E.L. Malikova1 1 V.S. Sobolev Institute of Geology and Mineralogy, Sibirian Branch Russian Academy of Sciences, Novosibirsk, Russia 2Novosibirsk State University, Novosibirsk, Russia
3Institute of Geography, Russian Academy of Sciences, Moscow, Russia
4Lomonosov Moscow State University,Moscow, Russia
The article examines the structure, composition, and textural features of the griva unit of the Volchia Griva section and the paragenetically associated relief. Additional data on the aeolian origin of the griva unit and griva relief have been obtained. OSL and ICS dating of the Volchya Griva section allowed us to attribute the formation time of the Griva unit to the epoch of the last glaciation and to correlated it with MIS 2 in its entire volume. It has been confirmed that the formation of aeolian relief and the activation of aeolian processes occurred during the cold glacial periods of the late Pleistocene with the predominance of southwesterly winds. The established textural features of the griva unit section are similar in textural and structural characteristics to the niveo-aeolian sands of the Upper Pleistocene, which were formed in cold, periglacial, arid regions of the world and distributed along the southern edge of the ice sheets of the last glaciation from Northwestern Europe to Western Siberia and Alaska. The formation of a deflationary truncation and of a mega-yardangs system in the northern part of the Lake Chany basin indicates a significant activation of aeolian processes at the boundary between the formation of the lower and upper horizons of the griva unit. The orientation of the griva relief, coinciding with the prevailing direction of modern winds, indicates the same direction of winds during the cold and warm epochs of the Quaternary in the south of Western Siberia. The completeness of the structure of the Volchya Griva section, corresponding to the epoch of the last glaciation and MIS 2, the confinement to this section of the largest in Eurasia location of the remains of the mammoth fauna, distinct lithological characteristics, a fairly high degree of its study allow us to consider this section as one of the typical for the Upper Pleistocene of Siberia and to consider it as a stratotype of the griva unit, widespread in this territory, which should be distinguished into an independent Baraba horizon (suite) for the south of Western Siberia, including the Eltsovka and Bagan loesses and the Suma soil separating them
T. G. Shumilova1, S. I. Isaenko1, V. N. Bocharov2, V. V. Ulyashev1, S. A. Svetov3, D. A. Mandrygina4, A. A. Zubov1, N. S. Kovalchuck1, N. I. Maksimenko1, V. P. Lutoev1, V. K. Kis5
1 N.P. Yushkin Institute of Geology Komi SC, UB RAS, Syktyvkar, Russia
2St. Petersburg State University, St. Petersburg, Russia
3 Institute of Geology of the Karelian Research Centre of the Russian Academy of Sciences, Petrozavodsk, Russia
4 A.N. Zavaritsky Institute of Geology and Geochemistry, UB RAS, Eekaterinburg, Russia
5 HUN-REN Centre for Energy Research, Budapest, Hungary
Keywords: karite, diamond, meteorite craters, impact metamorphism, fossils.
In the paper, the detail features of karite – the diamond (diamond-containing) fossils of the Kara meteorite crater formed after organic matter, generally after wood fragments, studied by a wide list of modern analytical methods are presented, including structural data at atomic resolution level, chemical composition and spectroscopic characteristics. The diagnostic features, formation mechanism and ontogenic specificity are analyzed. As a result of a detailed study of the ontogenetic specificity, structural and chemical composition of the diamond fossils a fundamental difference in the mechanism of formation from typical paramorphoses and pseudomorphoses has been established, there they have been classified as pseudo-paramorphoses. Taking into account special conditions for the described aggregates of diamond and other forms of carbon formation from organic matter by impact, it is proposed to differ a special variety of fossils – impact fossils. The prospects for using of the diamond fossils for geological studies and application in carbon materials field are estimated.
V.F. Smol’kin1, A.V. Mokrushin2,3 1Vernadsky State Geological Museum of the Russian Academy of Sciences, Moscow, Russia
2Geological Institute, Kola Science Centre of the Russian Academy of Sciences, Apatity, Russia
3Apatity branch of Murmansk Arctic University, Apatity, Russia
Keywords: Paleoproterozoic, gabbro, clinopyroxene, wehrlites, ferropicrites, dyke, sulphide Cu-Ni ore deposits, geochemistry, isotopes, genesis, Pechenga, Russia
Located in the north-west of the Murmansk Region, the sulphide Cu-Ni ore deposits were discovered in 1930s. Nowadays they provide approximately 8-10% of the nickel mining in Russia. The deposits are spatially associated with the serpentinite massifs, which have long been pertained to either the ophiolitic complex or basalt magma differentiates. The magma is regionally represented by the wide-spread fields of pillow lavas and gabbro-diabase sills. The ultramafic ferropicritic volcanics, which alternate in cross-section with lavas and basaltic tuffs, were discovered in 1970s. Initially the ore-bearing massifs were intrusions composed by peridotites (wehrlites), clinopyroxenites, and gabbro, which were tectonically metamorphosed during the Svecofennian tectonic genesis. Basing on petrological, geochemical, and isotopic research, scientists have proved that ferropicritic volcanics and ore-bearing intrusions are genetically bonded. The paper concerns the processes of differentiation of all the ferropicritic magma facies, i.e., intrusive (ore and ore-free intrusions), volcanogenic (massive and pillow lavas, stratified flows, sills), and dike ones (dike bodies, cross-cutting intrusions, and dike swarms in the Archean setting). Their relations, period and sequence of formation have been revealed. We also discuss the role that the processes of contamination and assimilation of the Archean basement rocks and hosting sulphide carbonaceous schists have played in sulphide ore formation.
I.D. Timoshina1, L.S. Borisova1, A.N. Fomin3 1Trofimuk Institute of Petroleum Geology and Geophysics, 630090, Novosibirsk, Koptug ave. 3, Russia
Keywords: North Tunguska Oil and Gas Region, Paleozoic, kerogens, asphaltenes, biomarker hydrocarbons, type and catagenesis of organic matter, hydrocarbon migration.
The organic matter (OM) of the terrigenous coal-bearing strata of the Tunguska series (C2-P) and the Khanar formation (C2-3), as well as the Devonian carbonate rocks of the North Tunguska OGR, have experienced a complex geological history due to strong heating by traps. Because of this, the values of biomarker genetic parameters C27/C17 in n-alkanes, C29/C27 in steranes, hopanes/tricyclanes decrease in a number of terrestrial bitumens, and the tricyclane index ITC is likely to be altered by the migration effects of accumulation/dispersion of low-molecular compounds. The sterane maturity coefficient in most samples has undergone thermal inversion and is unsuitable for determining the level of catagenesis. Devonian samples as a whole probably contain marine OM (low δ13C; high HI in the insoluble residue and in kerogen, H/Cat in kerogen; in the diagram Pr/nC17 – Ph/nC18
are at the boundary or in the field of type II kerogen; low nC27/nC17 and C29/C27 are characteristic), although in the kerogen of the Manturovka formation (D1), isotopic and pyrolytic characteristics are distorted, possibly due to high catagenesis. The coal-bearing strata contain terrestrial OM (low HI in kerogens; high nC27/nC17, C29/C27
in steranes, hopanes/tricyclanes for the Khanar formation). The genetic characteristics of the saturated fractions of bitumen nC27/nC17, C29/C27 in steranes, hopanes/tricyclanes in several samples of the Upper Paleozoic are significantly distorted due to the catagenetic redistribution of compounds in favor of low-molecular compounds. According to the elemental composition of kerogen, half of the samples of the Khanar formation and the Tunguska series can be attributed to type III kerogen, and the other half to type IV, probably due to the high level of thermal transformation by the introductions of traps. In this regard, catagenesis for carbon–permian increases generally from the bottom up along the section from the MK2 gradation to apocatagenesis (changes in Rovt, MPI-1 in the aromatic fraction of bitumen, H/Cat in kerogens and asphaltenes).
R.A. Valiullin, M.S. Gayazov, F.F. Davletshin
Ufa University of Science and Technology, Ufa, Russia
Keywords: active thermometry, temperature, horizontal well, fluid flow, experimental research, free convection
This article is devoted to the development and experimental validation of an active thermometry method for quantitatively assessing fluid flow rate in horizontal wells. Two approaches were studied experimentally using a physical well model under single-phase flow conditions: a calorimetric approach (based on the integral superheating of a homogenized flow) and a convective approach based on the dependence of the heated pipe wall temperature on the flow rate. It was established that the Richardson number (Ri) is a key criterion determining the heat transfer mechanism. At Ri > 1 (low flow rate regime), thermogravitational effects dominate, causing significant temperature stratification of the flow. It is shown that under such conditions, the calorimetric method is more reliable and allows for flow rate determination with high accuracy (deviation no more than 10%). At the same time, the limitations of the convective method, the interpretation of which in this study took into account only the forced component of heat transfer (the Dittus-Belter model), are identified: it is correct only for Ri < 0.1 (high flow rates). The work lays the methodological basis for further development of the method, the key areas of which are the complication of the convective model to take into account free (natural) convection and the adaptation of both approaches to the conditions of multiphase flows.
The article summarizes published and new geological, geochronological, biogeographical, paleomagnetic, and petrological-geochemical data to support the tectonic zoning of the Central Asian Fold Belt (CAFB) and its Vendian-Paleozoic geodynamic evolution as a complex folded structure consisting of deformed fragments of collisional and accretionary orogens. It has been shown that the Central Asian-Siberian Platform was formed in the zone of junction of the collisional and accretionary margins of the Siberian craton, similar to the modern tectonic interactions between the Indo-Atlantic and Pacific global tectonic segments of the Earth and Eurasia. It has been shown that in the Vendian and Early Ordovician, there were two active margins around the Siberian craton: the collisional Tuvo-Mongolian margin and the accretionary Kuznetsk-Altai margin, which separated the craton from the tectonic plates of the Paleo-Asian Ocean (Indo-Atlantic segment) and the Paleo-Pacific Ocean (Pacific segment), respectively.A distinctive feature of the Paleoasiatic Ocean plate is complex structure, which includes fragments of oceanic crust and Precambrian Gondwana microcontinents with fragments of the Grenville orogeny. Fragmentary Grenville zircons (1.3-0.9 billion years old) are widely found in the Vendian-Paleozoic sedimentary deposits of various geodynamic settings of the collisional orogen. A distinctive feature of the accretion orogen is the widespread presence of oceanic crust fragments and the absence of Precambrian blocks of Gondwana, and as a result, the absence of Granville-age clastic zircons in the Vendian-Paleozoic sedimentary rocks of various geodynamic settings. The Early-to-Middle Paleozoic Charysh-Terekta-Ulagan-Sayan-Olkhon suture-shear zone separates the collisional orogen from the shelf of the back arc basin located in the northern part of the Altai-Sayan folded region framed by the Siberian craton. The suture-shear zone consists of fragments of the Vendian-Early Paleozoic oceanic crust of the Back Arc basin, Ordovician blue shales and Ordovician-Silurian turbidites, Late Silurian-Devonian collisional metamorphic rocks and granites. Based on the structural position of the suture-shear zone and the data of petrological and geochronological studies, it is concluded that it is a subduction-collision complex formed at the site of the back-arc basin of the Vendian-Cambrian Tuva-Mongolian island arc. Late Paleozoic shifts and thrusts manifested themselves in the CAFB in the Late Devonian-Early Carboniferous as a result of the collision of the Kazakhstan-Baikal orogen (composite continent) with the Siberian craton with the formation of the North Asian continent, and in the Late Carboniferous-Triassic as a result of the collision of the East European and North Asian continents. As a result of collisional events, the initially linear structures of the collisional and accretionary orogens were deformed into large oroclinal folds, divided by shifts and thrusts into many fragments, where the Vendian-Paleozoic structures are complicated by thrust-fold deformations.
A. A. Tamrazyan, R. K. Gasparyan, A. H. Avdalyan, M. V. Ohanyan
Nazarov Institute of Geophysics and Engineering Seismology of the National Academy of Sciences of the Republic of Armenia, Gyumri, Armenia
Keywords: magnetic survey, anomalous magnetic field, ultrabasic rocks, hydrothermal alteration, tectonic faults, Lori Region.
The results of magnetic survey investigations conducted in the floodplain areas of the Yellow and Black rivers in the Lori Region of Armenia (northern part of the Republic of Armenia) are presented. Based on field observations, digital and graphical maps of the anomalous magnetic field (∆Ta) and its three-dimensional model were constructed. Analysis of the anomalous magnetic field structure made it possible to identify a number of positive and negative anomalous zones associated with geological formations differing in magnetic properties. It has been shown that the positive anomalies are caused by the presence of ultrabasic rocks (peridotites, pyroxenites) exposed along the left bank of the Yellow River and the right bank of the Black River. An extensive negative anomaly zone has been identified and interpreted as a reflection of a tectonic fault zone and the adjacent thick area of hydrothermally altered rocks. Comparison with the data on the physical properties of rocks confirmed the high contrast of magnetic characteristics between the ultrabasic and ore-hosting rocks.
The article presents algorithms for numerical modeling of electrical micrologging signals and calculation results in geoelectric models of impermeable rocks and the borehole environment of a porous, permeable reservoir. This research may be useful for developing an integrated approach to the quantitative interpretation of electrical logging data. A joint numerical analysis of electrical logs measured by conventional probes and microprobes will enable refining the radial electrical resistivity distribution in the borehole environment of oil-gas reservoirs. This, in turn, will provide additional information when jointly solving the problem of drilling mud filtration and numerical inversion of electrical logging data, resulting in a more accurate assessment of reservoir porosity and permeability. We have developed software for numerical simulation of electrical micrologging signals – those from a microgradient, micropotential and microlaterolog probe with focusing. We employ a finite element algorithm with an arbitrary position of the probes in a cylindrically-layered geoelectric model, and a finite difference algorithm for a microgradient and micropotential probe in a horizontally-layered model. Test calculations of the signals in geoelectric models of Western Siberia terrigenous deposits are presented. The models describe impermeable sediments as well as layers with the mud cake and invaded zone at different resistivity ratios. The model parameters correspond to Lower Cretaceous oil-gas reservoirs exposed with polymer-clay drilling muds. The analysis of the calculated micrologging signals reflects a small investigation depth of microgradient and micropotential probes, and a strong dependence of the signals on the drilling mud and mud cake resistivities. Numerical modeling in the class of a cylindrically-layered model has allowed us to obtain the radial resistivity change in the borehole environment of an oil-gas reservoir.
I.D. Novoselov1,2, S.V. Ivanov1,2, Yu.N. Bataleva1, Yu.N. Palyanov1,2 1V. S. Sobolev Institute of Geology and Mineralogy of the Siberian Branch of the Russian Academy of Sciences, Novosibirsk, Russia
2Novosibirsk State University, Novosibirsk, Russia
Keywords: C-O-S fluid, garnet, sulfide, high-pressure experiment, mantle metasomatism, diamond dissolution
Experimental researches focusing on modeling of interaction between eclogitic and lherzolitic garnets with reduced and oxidized sulfur-rich fluids are conducted using multianvil high-pressure apparatus of “split-sphere” type (BARS). Experiments are carried out in garnet-sulfur-carbon and garnet-anhydrite-carbon systems at the pressure of 6.3 GPa and the temperatures of 1150, 1300, and 1450 °С in graphite ampules, as well as in Pt-ampules with hematite buffering container. It is experimentally demonstrated that interaction of both reduced and oxidized sulfur-rich fluids with mantle garnets leads to their partial dissolution and recrystallization, and to the formation of zoned crystals with decreased iron content in rims. Apart from that, this interaction also results in (1) garnet carbonatisation accompanied by formation of the magnesite±dolomite+kyanite+coesite assemblage, and (2) garnet sulfidation with formation of pyrite (1150-1300 °С) or sulfide melt (1450 °С) as inclusions in garnets and in interstitial space. As a result of conducted experimental researches it is established that indicatory characteristics of mantle garnets that underwent metasomatism by sulfur-rich agents, are decreased FeO content in peripheral crystal zones relatively to their centers, and formation of sulfide inclusion in the zones borders. In this paper we also present the first data on diamond dissolution in the silicate-sulfur-carbon systems under lithospheric mantle P,T-parameters that simulate mantle metasomatism of garnet-bearing lithologies by sulfur-rich fluids. It is found that under such conditions diamond crystals undergo partial dissolution resulting in formation of characteristic etching pits (negative trigons on {111} and rectangles on {100}).
Spectral decomposition is a widely used method of qualitative seismic interpretation, whose key limitation lies in the subjective selection of frequency components for visualization. Existing approaches based on the analysis of the integral Fourier spectrum do not account for the temporal localization of the signal’s spectral content. This study introduces a new method for the automatic selection of frequencies based on approximating local spectra obtained via the Short-Time Fourier Transform (STFT) with a sum of three Morlet wavelet spectra. This approach enables the extraction of time-dependent frequency trajectories that capture the evolution of the signal’s spectral content, rather than relying on a static set of frequencies over the entire interval. The optimization problem is solved using the differential evolution algorithm. The method was tested on data from fields of the West Siberian petroleum province. Quantitative evaluation using Shannon and Rényi entropy metrics, as well as a colorfulness metric, demonstrated increased informativeness of RGB images compared with traditional approaches. The proposed method reduces interpretation subjectivity and ensures reproducibility of results.
O.V. Furman1, Yu.V. Bataleva1, Yu.M. Borzdov1, Yu.N. Palyanov1,2 1V.S. Sobolev Institute of Geology and Mineralogy, Siberian Branch of the Russian Academy of Sciences, Novosibirsk, Russia 2Novosibirsk State University, Novosibirsk, Russia
Experimental studies aimed at assessing the possibility of diamond crystallization during interactions of alkaline earth and transition metal carbonates with sulfur, as well as at characterizing the obtained diamond crystals and inclusions in them, were carried out on a multi-anvil high-pressure "split sphere" apparatus (BARS). The experiments were performed at constant P,T,t-parameters: 6.3 GPa, 1550 ºС and a duration of 20 hours, in the Mg,Ca-carbonate-sulfur system with different CaO/MgO ratios and Fe,Mg,Ca-carbonate-sulfur system with variable FeO/CaO/MgO proportions. It was experimentally established that in the alkaline earth carbonate-sulfur systems, a Ca,Mg-carbonate melt with dissolved sulfur (1.2-6.0 wt.%) is formed, which is a diamond growth medium. The stable growth form of diamond crystals is the octahedron, and an increase in the Ca# of the system is accompanied by an increase in the growth rate of the {111} faces. It was demonstrated that in the Fe,Mg,Ca-carbonate–sulfur system, the crystallization medium and the source of diamond carbon is the Fe,Mg,Ca-carbonate melt with dissolved sulfur, and diamond growth occurs as a result of the redox interaction of the sulfide and carbonate melts. With an increase in the ferruginousity of the system from 0.41 to 0.78, there occurs (1) an increase in the growth rate of the {100} faces (from 1.0 to 5.4 μm/h); (2) a change in the predominant elements of the octahedron face microrelief from triangular growth layers to hexagonal vicinals; and (3) an increase in the number and size of inclusions, as well as the evolution of their phase composition. Diamond inclusions are formed by melt preservation on the {100} faces during the transformation of a cuboctahedron into an octahedron. The inclusions contain quenched carbonate melt (quenching phases — carbonate, magnetite, and graphite), sulfur melt, and Fe-S-O melt. The discovery of a carbonate+magnetite+graphite association in the inclusions confirms the occurrence of a siderite redox dissociation reaction (3FeCO3 = Fe3O4
+ 3C0 + 2.5O2 fluid) at the P,T-parameters of the lithospheric mantle. These results shed light on the possible origin of magnetite inclusions in upper-mantle diamonds and suggest that the presence of magnetite in syngenetic inclusions may be an indicator of the participation of iron-bearing carbonates in natural diamond formation processes. The results of the conducted studies indicate that Mg,Ca- or Fe,Mg,Ca-carbonate melts with dissolved sulfur can be classified as natural diamond-forming environments, and the identified features of the morphology of diamond crystals, the specifics of its growth and the composition of inclusions depending on the cationic composition of the carbonate melt with dissolved sulfur can be used as indicators of diamond crystallization in similar melts in nature.
V.S. Shatsky1,2,3, A.L. Ragozin1, V.V. Kalinina1 1 1V.S. Sobolev Institute of Geology and Mineralogy, Siberian Branch of the Russian Academy of Science, Novosibirsk, Russia
2Novosibirsk State University, Novosibirsk, Russia
3A.P. Vinogradov Institute of Geochemistry, Siberian Branch of the Russian Academy of Sciences, Irkutsk
Keywords: Siberian Craton, inclusions in diamonds, fluoride melts, diamond formation, mantle, subduction zone
This paper presents new evidence for fluorine enrichment in the diamond-forming mantle of the Siberian Craton. For the first time, we have discovered inclusions containing calcium and aluminum fluorides in diamonds from placers in the northeast of Siberia. In contrast to microinclusions in fibrous diamonds and coated diamonds, the inclusions we studied in diamonds from the northeastern Siberian Craton placers can be interpreted as fluoride melts. In diamond ISTD-119, inclusions are oriented parallel to the octahedron faces and can be considered syngenetic. At the same time, in diamond ISTD-124, an elongated inclusion is oriented parallel to slip lines. This provides grounds to believe that the formation of the inclusion was synchronous with the stage of diamond deformation. In variety V diamonds XLS-147 and ISTD-193, the morphology of inclusions located in the central parts of the crystals allows them to be interpreted as healed fractures. Within the inclusions, fluorine is present as compounds with calcium, having stoichiometry close to fluorite. The inclusions exhibit areas consisting of calcium fluorides and areas consisting of carbonates and/or iron oxides. In variety V diamond XLS-147, aluminosilicate inclusions and inclusions consisting of aluminosilicate and fluoride parts were identified. However, unlike inclusions in diamonds ISTD-119, ISTD-193, and ISTD-124, the fluoride part of the inclusions in diamond XLS-147 is represented by aluminum fluorides. There is a body of evidence for the growth of type V diamonds in a subduction zone. The compositional variations of the inclusions we studied indicate immiscibility of fluoride melts with aluminosilicate and carbonatite melts. The inclusions we have investigated testify to a fluorine-enriched diamond-forming mantle of the Siberian Craton at the time of diamond formation.
S.I. Starostina1,2, O.L. Gaskova2, N.V. Yurkevich2,3 1Trofimuk Institute of Petroleum Geology and Geophysics Siberian Branch of the Russian Academy of Sciences, Novosibirsk, Russia
2V.S. Sobolev Institute of Geology and Mineralogy Siberian Branch of the Russian Academy of Sciences, Novosibirsk, Russia
3Peoples' Friendship University of Russia named after Patrice Lumumba, Moscow, Russia
Keywords: Thermodynamic modeling, wastes of flotation enrichment, sulphide ores, alternate resources.
A thermodynamic model of the interaction between surface waters and the wastes of flotation enrichment of sulfide PGE–Cu–Ni ores from the ore region under consideration (Krasnoyarsk krai) is presented. The relevance of the study is determined by the need to assess the long-term stability of mineral associations. The aim of the work is to establish the patterns of transformation of mineral associations during long-term storage. The initial information was provided by mineralogical and chemical composition of samples from two pits, as well as the chemical composition of water extracts [Starostina et al., 2025]. Calculations were carried out in the solid–water–gas system under variations of Eh, simulating different degrees of system openness to atmospheric oxygen (standard T–P, pCO2(gas)
= 10–3.5 atm). Based on the modeling results, it was found that pyrrhotite is stable under extremely reducing conditions (pO2(gas) = 10–79 atm), where the dissociation of water into atomic oxygen and hydrogen may occur. In general, the obtained models reflect the transition from sulfide to oxide–silicate associations with a decrease in the number of mineral phases as oxidation progresses. The modeled associations correspond well with mineral parageneses observed in polished sections. It was shown that the material retains its primary mineral structure even after decades of storage, which is explained by the high content of rock-forming minerals within a dense clay matrix that prevents oxygen and moisture from penetrating in amounts sufficient for intensive oxidation. The results obtained are recommended for use in the development of technological schemes for the recovery of potentially valuable metals from the flotation wastes of sulfide PGE–Cu–Ni ores.
S.N. Rudneva, G.A. Babinb , P.A. Serovc, A.V. Somsikovad a V.S. Sobolev institute of Geology and Mineralogy, Siberian Branch of the Russian Academy of Sciences, Novosibirsk, Russia b A.P. Karpinsky Russian Geological Research institute, St.Petersburg, Russia с Geological institute of the Kola Science Center, Russian Academy of Sciences, Apatity, Russia d Vernadsky Institute of Geochemistry and Analytical Chemistry of the Russian Academy of Sciences, Moscow, Russia
Keywords: Altai–Sayan Fold Belt; Western Sayan; granitoid and gabbroid magmatism; geochemistry; Nd and Sr isotopes
This study synthesizes petrochemical, geochemical, and isotopic (Sm–Nd and Rb–Sr) data on granitoid and gabbroid complexes of the Western Sayan, formed in a range of geodynamic settings (including island arc, accretion–collision, transform–shear, and active continental margin environments) between the Late Vendian and Late Devonian. The results provide constraints on the physicochemical conditions of parental melt generation, the nature of magma sources, and their temporal evolution throughout successive geodynamic stages.
These findings highlight the long-term evolution of magma sources in response to changing geodynamic regimes during the Vend–Paleozoic development of the Western Sayan. The intrusive complexes display a systematic decrease in ɛNd and increase 87Sr/86Sr0 values in granitoid and gabbroid complexes from early to later geodynamic stages: island arc (545–524 Ma, ɛNd = +7.5 – +4.9, 87Sr/86Sr0
= 0.7042–0.7056), accretion–collision (505–460 Ma, ɛNd = +6.9 – +0.6, 87Sr/86Sr0
= 0.7036–0.7041), transform–shear (437–433 Ma, ɛNd = +8.4 – +7.2, 87Sr/86Sr0 = 0.7031–0.7057), and active continental margin (425–370 Ma, ɛNd = +5.7 – +1.0, 87Sr/86Sr0 = 0.7035–0.7103). This progressive shift reflects a declining contribution of mantle sources (island-arc and oceanic types) and a concomitant increase in the role of ancient crustal components (metamorphic complexes, turbidites, and flysch-type sediments) in the generation of parental magmas.
A.L. Elbaev1, I.V. Gordienko1, V.B. Khubanov2, M.S. Skripnikov1, D.E. Yudin1, A.M. Khubanova2 1Dobretsov Geological Institute SB RAS, Ulan-Ude, Russia 2Schmidt Institute of Physics of the Earth RAS, Moscow, Russia
The composition of volcano-terrigenous formations and age of detrital zircon from the tuff-turbidite series sandstones of the Dzhida zone of the Central Asian Orogenic Belt were studied. The sandstones of this formation, in terms of their mineralogical and petrochemical characteristics, correspond to feldspar graywackes and belong to the rocks of the first sedimentation cycle. The main volume of detrital material is represented by volcanics and, to a lesser extent, plagioclase grains. Relatively low values of chemical index CIA (58-68) indicate moderate or weak chemical weathering of lithic components, that is a low maturity degree of the detrital material formed due to the source rocks mechanical destruction. The distribution curve of U-Pb ages of zircon from sandstones of the tuff-turbidite series has a bimodal character with peaks at 530 Ma and 510 Ma. The studied rocks do not contain zircons of Neoproterozoic age. The greywacke composition of the studied rocks, the low maturity degree and the distribution of zircon grains U-Pb ages suggest the formation of these rocks in the forearc basin conditions due to the removal of material from local sources – Early Cambrian volcanic rocks of the Dzhida ensimatic island arc.
S.V. Rudko1, S.V. Malyshev2, M. Ovtcharova3, A.V. Drazdova1, I.V. Fedyukin4, V. B. Khubanov4, A.S. Dubensky1, V.S. Sheshukov1. 1 Geological Institute of the Russian Academy of Sciences, Moscow, Russia
2Institute of Earth Sciences, Saint Petersburg, Russia
3University of Geneva, Geneva, Switzerland4Schmidt Institute of Physics of the Earth of the Russian Academy of Sciences, Moscow, Russia
Using LA ICP MS dating of zircons, the age of the tuff (633±7 million years) of the Bolshoi Patom Formation at the base of the Vendian reference section in the south of the Siberian Platform (Ura Uplift) was estimated. The Vendian of the Siberian Platform was found to include the last Cryogenian (Marinoan) glaciation, and the postglacial sequence of the Vendian corresponds to the Ediacaran. In light of the obtained dating, the chronostratigraphy of the Riphean-Vendian deposits on the Ura Uplift and in adjacent areas is considered. The available geochronological and sequence stratigraphic data indicate the presence of hidden stratigraphic unconformity above the glacial horizon at the base of the Vendian, caused by glacio-isostasy.
R. Kabiev1, A. Malmakin1, S. Volkovskii1, A. Gribaev1, I. Sharkov1, A. Kulikov1, D. Kirgizov2, E. Asadullin2 1 ITMO University, Saint-Petersburg, Russia
2Institute R&D TatNIPIneft, TATNEFT, Bugulma, Russia
Keywords: gamma spectrometer, pulse analyzer, FPGA, digital signal processing, pulse pile-up, spectrometric gamma logging
This paper presents the results of developing a pulse analyzer for a borehole geophysical instrument intended for spectrometric gamma-ray logging. The module is implemented using a field-programmable gate array and enables real-time signal processing. An algorithm for converting biexponential responses of a scintillation detector into trapezoidal pulses is proposed. The efficiency of the implemented algorithm has been demonstrated in resolving pile-up pulses with a time delay of 300 ns. Using calibrated gamma-ray sources — Am‑241, Eu‑152, Cs‑137, Co‑60, and Th‑228 — the system's energy coverage in the range of 50 to 3000 keV is confirmed. The pulse analyzer features universal architecture and is compatible with various types of gamma-ray detectors.
S.V. Khromykh1, D.V. Semenova1, M.D. Tsareva1, E.A. Il’icheva1 1V.S. Sobolev Institute of Geology and Mineralogy Siberian Branch of Russian Academy of Sciences,
Novosibirsk, Russia
Keywords: Rudny Altai, Late Paleozoic magmatism, correlation of igneous complexes, gabbro, granites, Central Asian Orogenic Belt.
The article presents the results of geochronological, geochemical and isotopic studies of intrusive complexes in the central and southern parts of Rudny Altai, which until recently have been practically uncharacterized using modern research methods. The results of U-Pb dating of zircon grains from igneous rocks (26 determinations) made it possible to establish 4 stages of endogenous activity: 1) Late Devonian (~ 370–360 Ma); 2) the end of the Early Carboniferous (~ 330–320 Ma); 3) Middle–Late Carboniferous (~ 315–305 Ma); 4) Early Permian (300–286 Ma). During each stage, both mafic and granitoid magmatism was manifested, which indicates the active development of mantle-crust interaction processes. An examination of the geochemical characteristics of the studied rocks allowed us to draw conclusions about the sources of magmas and the conditions of their melting, while comparison with geological and geochronological data from neighboring regions allowed us to determine the most likely geodynamic regimes for the manifestation of intrusive magmatism in the region. In the Late Devonian, magmatism occurred in a subduction setting on the active margin of the Siberian continent. At the end of the Early Carboniferous, magmatism was associated with the onset of orogenic processes during the formation of the Zaisan folded system orogenic structure. In the Middle to Late Carboniferous, magmatic activity reflects the onset of post-orogenic extension. Early Permian magmatism is due to a combination of post-orogenic extension and the activity of the Tarim large igneous province, formed as a result of the impact of the mantle plume of the same name on the lithosphere. Special attention is given to metallogenic aspects, and suggestions are made regarding the absence of ore deposits associated with intrusive magmatism in the region..
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