K.Yu. Vasileva1,2, M.A. Rogov1,3, V.A. Zakharov 1, B.L. Nikitenko 4, E.B. Pestchevitskaya 4,
A.V. Yadrenkin4, N.K. Lebedeva4, A.A. Goryacheva4, S.N. Khafaeva4, N.A. Malyshev5, V.E. Verzhbitsky5, G.V. Ulyanov6, V.V. Obmetko5, A.A. Borodulin5 1Geological institute of RAS, Moscow, Russia 2Saint Petersburg State University, St. Petersburg, Russia 3Arctic Research Center (ARC), Moscow, Russia 4The Trofimuk Institute of Petroleum Geology and Geophysics, Siberian Branch of the Russian Academy of Sciences (IPGG SB RAS), Novosibirsk,Russia 5Rosneft, Moscow, Russia 6JSC “RN-GIR” Moscow branch – center for technical competentions IGIRGI, Moscow, Russia
We present data on the findings of glendonites (pseudomorphs of the cold-water mineral ikaite) in Permian, Jurassic and Lower Cretaceous sedimentary rocks, penetrated by well KS-1, drilled on the coast of the Laptev Sea. This is the only section in the world that contains glendonites of both Paleozoic and Mesozoic age, belonging to a vast time interval including three geological systems. Glendonites are found here in all stages from which they are known in northern Siberia, with the exception of those stratigraphic intervals in which glendonite finds are comparatively rare (Oxfordian, Ryazanian and Valanginian stages). KS-1 well is a unique natural archive, which reflects the most significant cooling events in the studied region during the late Paleozoic-Mesozoic.
B.B. Kochnev1,2, N.I. Vetrova2, E.V. Vetrov3, G.A. Karlova1 1Trofimuk Institute of Petroleum Geology and Geophysics SB RAS, Novosibirsk, Russia 2Sobolev Institute of Geology and Mineralogy SB RAS, Novosibirsk,Russia 3PJSC Polyus, Moscow, Russia
Keywords: Vendian, Cambrian, Ediacaran, Gorny Altai, Baratal Group, carbonate sedimentary rocks, geochemistry, carbon, oxygen and strontium isotopes, metasomatosis
The chemical and isotope (C, O, Sr) composition of carbonate deposits in three sections of the lower Baratal Group in the southeast of the Altai Mountains, which are considered as one of the oldest known fragments of the carbonate cover of oceanic uplifts preserved in the structure of the Central Asian folded belt, was studied. The contents of Fe, Mn and Sr and their ratios to each other, and to isotope parameters indicate a post-sedimentary alteration which varying within and between studied sections. For the least altered «Akkaya» section, the δ13C values are –0.4…+0.7‰, and the 87Sr/86Sr ratios vary from 0.70818 to 0.70833, which limits the age of sedimentation to the range of 550-520 Ma. In the «Kurai» and «Chagan-Uzun» sections, along with similar values, anomalously low values of 87Sr/86Sr down to 0.70662…0.70701 are observed, which are often accompanied by a decrease in δ18O values and an increase in Mn content. These unusual characteristics of carbonates are proposed to be the result of influence of the metasomatic fluids tied with underlying basalts and spatially related to Kuvai regional fault zone. In the «Kurai» section, skeletal small-shelly fossils Cambrotubulus were found, which are not known to be older than 550 Ma, and confirms the transitional terminal Precambrian – earliest Phanerozoic age of the basal sequences of Baratal Group.
I.F. Chayka1, S.Yu. Stepanov 2, A.V. Kozlov3, F.D. Sandalov4, R.S. Palamarchuk2, N.I. Baykov1, V.S. Zhdanova5, V.D. Abramova4 1Korzhinskii Institute of Experimental Mineralogy RAS, Chernogolovka, Russia ivanlab211@gmail.com 2Natural science museum of the Ilmeny Reserve, Southern Ural center for mineralogy and geoecology UB RAS, Miass, Russia 3Saint Petersburg Mining University of Empress Catherine II, Saint-Petersburg, Russia 4Institute of geology of ore deposits, petrography, mineralogy and geochemistry RAS, Moscow, Russia 5Zavaritsky Institute of Geology and Geochemistry UB RAS, Ekaterinburg, Russia
Keywords: skarn, Cu-Fe skarn formation, native gold, gabbro, S isotopes, Ural Platinum Belt
Skarn-type Fe and Cu deposits enriched in Au are widespread within the Tagil–Magnitogorsk megazone of the Ural Fold Belt and are primarily associated with felsic to intermediate intrusions. In the Northern Urals, Fe–Cu skarn-type deposits and ore occurrences are found in the exocontacts of gabbroic phases of the polyphase intrusions of the Ural Platinum Belt. These systems are of particular interest as they represent the terminal (hydrothermal–metasomatic) stage in the fractionation of chalcophile and noble metals within magmatic systems of young island arcs. The metasomatic rocks developed in the exocontact zone of the Knyaspa intrusion, investigated in this study, contain ore-grade concentrations of Fe and Cu (0.5–5 wt%) and Au (0.2–14 g/t), and are classified as belonging to the Cu–Fe skarn formation of the Ural belt. The geological, mineralogical, and geochemical characteristics of this occurrence are largely typical of Cu–Au skarn deposits and are genetically linked with the gabbroic phase of the intrusion, rather than with the dioritic one. The metasomatic rocks formed after andesibasalts of the Pavda Formation. The following sequence of their formation has been reconstructed: (1) amphibole–plagioclase or clinopyroxene–plagioclase hornfelses (hornfels phase); (2 epidote-bearing assemblages with clinopyroxene or garnet (pre-ore skarn stage of the hydrothermal-metasomatic phase); (3) clinopyroxene–actinolite–epidote associations with magnetite and Cu sulfides (ore skarn stage of the hydrothermal-metasomatic phase); (4) largely zeolite assemblages (late hydrothermal stage of the hydrothermal-metasomatic phase) and (5) supergene phase. The estimated temperatures for the formation of primary sulfide mineralization range from 300 to 400 °C. Formation of native gold, which has exclusively broad compositional range in terms of Cu and Ag admixtures, took place at lower temperatures (approximately 100–250 °C) and probably continued during supergene phase Based on δ34S values in sulfides and the geochemistry of chalcophile elements in skarns, the ore elements were probably orthomagmatic. However, the mobilization of S and Cu from the volcanogenic massive sulfide deposits of the Shemur Formation through their assimilation by the intrusion cannot be ruled out, as well. Regardless of the source, the redox state of sulfur was significantly shifted toward oxidized species (S⁶⁺ or S⁴⁺), resulting in unusually low δ³⁴S values (–6 to –4‰) in the sulfides of the metasomatic rocks.
The first experimental data on the relationship between the carbon dioxide content in minerals of the lazurite-type minerals (LTM) and its partial pressure in the gas phase and temperature in the range corresponding to the lazurite formation process at deposits in the Southern Baikal region have been obtained. The content of structural CO2 species was determined by IR- Fourier spectroscopy. It depends more on temperature than on the partial pressure of CO2
and is maximum for cubic lazurites at 500 °C (0.05-0.07 formula units, f.u.), decreasing to 0.01-0.03 f.u. both when the temperature decreases (460 °C) and when it increases (560 °C). A positive dependence of CO2 content on O2 fugacity in the system has been noted. LTM with an orthorhombic structure (vladimirivanovite) retains CO2 less effectively, with its content decreasing from the initial (natural) 0.08 to 0.01-0.02 f.u. in the specified temperature range of 460-560 °C. The experiments with exposure at 560
oC and subsequent cooling to 460 or 360 oC show the lack of retrograde CO2 solubility in LTM under saturation from gas phase. According to data on CO2 content, cubic lazurites with incommensurate 3D modulation of the structure could have formed at a temperature of about 500 °C, a partial CO2 pressure of ~1.4-2.2 bar, and fO2 at the level of the magnetite-hematite buffer. The high CO2 contents (0.15-0.3 f.u.) recorded in some LTMs may not be related to the direct absorption of CO2 from the gas (fluid) phase, but are the product of relatively low-temperature (<400 °C) transformations of carbon forms, leading to the association of CO2 and molecular forms of sulphur. This temperature range and the fugacity of volatile compounds corresponding to such forms of sulphur should be considered as possible conditions for the synthesis or modification of materials based on sodalite, nosaean and LTMs, which are promising as carbon dioxide absorbers or indicators.
The Mid-Atlantic Ridge within Iceland differs significantly in structure from other ridges. It consists of several modern rift zones with different kinematics and internal structure. At the same time, there are also several inactive rift zones, separated by block uplifts. This structural diversity is caused by the thermal influence of the Icelandic plume, which manifests itself in conditions of asymmetric spreading. To identify the conditions for the development of Icelandic rift zones and the features of their structure in connection with the cyclic plume activity, a physical modeling was used. The resulting model reflects the structure and development of Icelandic rift zones over the last 21.5 million years. It was shown that the kinematics and internal structure of rift zones are a consequence of the development of multi-scale overlaps of spreading centers. Between them, block uplifts arise, which in the modern topography are expressed as elevated peninsulas, mainly in the northern part of the island. The sizes of block uplifts depend on the distance between overlapping spreading axes. As the distance decreases, large uplifts are replaced by a series of small en-echelon blocks. The formation of this structural ensemble is the result of periodic increase in plume activity and its eastward displacement relative to the boundary of the lithospheric plates, which is caused by spreading asymmetry. There are two cycles of plume activity with different durations. The period of 7–8 million years reflects the complete cycle of formation and development of overlappings, and the period of 2–3 million years determines the evolution of the rift zone structure within the entire structural ensemble.
D.A. Nosov1, D.K. Dronov2, Y.G. Turbin2, I.S. Sizikov1. 1Institute of Automation and Electrometry of the Siberian Branch of the Russian Academy of Sciences, postal Novosibirsk, Russia
2Arctic and Antarctic Research Institute, St:Petersburg, Russia
The article presents the first experimental work with the GABL-PM absolute ballistic laser gravimeter on the pier, in ports and on board the ice-resistant platform (LSP) in the expedition "North Pole-42" (SP-42). During the tests, the parametric adjustment of the gravimeter was carried out in order to adapt the device for its operation on the LSP without using a gyrostabilized platform. The results of the GABL-PM measurements at the berth in St. Petersburg are shown, which are required as a reference for testing the gravimeter on the ship, as well as for linking variations in gravity acceleration measured on board the LSP with the Chekan-AM relative gravimeter to absolute values. The estimation of the RMS error of the GAB-PM measurement on board the LSP at various pitching parameters in the ports of St. Petersburg and Murmansk, as well as in the early days of the start of the drift of the North Pole-42 expedition, is given. Based on the measurement results, it was concluded that a gravimeter without a gyrostabilized platform with reduced accuracy values, on average up to 0.60 mGal, can be used to carry out measurements after freezing the vessel and when following all the points of a specially developed instruction.
1Institute of the Earth's Crust, Siberian Branch of the Russian Academy of Sciences, Irkutsk, Russia
Keywords: the Cenozoic, volcanism, Baikal Rift, Biryusa block, Siberian craton, pyroxenite mantle source
Based on an analysis of the hypsometric positions of lavas of different ages in the Iya-Uda volcanic field (~8 and ~4 Ma), it has been established that the main phase of intense relief dissection and activation of block movements along the Main Sayan Fault within the Biryusa block occurred in the late Miocene. Geochemical characteristics of the lavas, such as high values of the FCKANTMS parameter (0.46–0.77) [Yang et al., 2019] and the positions of figurative points on the CaO–MgO and TiO₂/Al₂O₃–SiO₂ diagrams, indicate melting of a garnet-pyroxenite mantle source rather than a typical peridotite mantle. The trace element composition of the rocks is consistent with intraplate basalts such as OIB. Variations in the Th/Nb and TiO₂/Yb ratios indicate that for lavas aged 4 Ma, the role of garnet in the melting zone increases, while for magmas aged 8 Ma, the contribution of the lithospheric mantle becomes more significant. The genesis of the enriched pyroxenite component in the lithosphere of the Biryusa block is most likely related to tectonic convergence processes during Late Cenozoic rifting, which led to a change in the volume of the crust and the involvement of lower crustal material into the mantle of the Siberian Craton. Thus, volcanism in the Iya-Uda volcanic field is the result of melting of heterogeneous and enriched lithospheric mantle.
Z.S. Nikiforova1, A.S. Borisenko2, V. L. Sukhoroslov3 1Diamond and Precious Metal Geology Institute of SB RAS, Republic of Sakha (Yakutia), Yakutsk, Russia 2 V.S. Sobolev Institute of Geology and Mineralogy SB RAS, Novosibirsk, Russia 3 Zarubezhtsvetmet JSC, Moscow, Russia
Keywords: eolian processes, relief, formation, eolian placers, distribution conditions, eolian gold, ventifacts, deflation, promising areas, Mongolia
The influence of Aeolian processes on the formation of gold-bearing Aeolian placers has not yet been adequately taken into account in Mongolia, although there is well-reasoned evidence in favor of their formation. Based on the identification of Aeolian gold, the conclusion is substantiated that the formation of gold-bearing placers involved not only hydrodynamic, but also Aeolian processes, which were widely manifested in the Quaternary. The presence of Aeolian gold placers in the troughs and basins of the blowout suggests the formation of gold-bearing Aeolian placers. An analysis of the patterns of distribution of Aeolian gold has shown that the formation of Aeolian gold placers on the territory of Mongolia is quite possible – actually Aeolian placers and placers of heterogeneous origin. Actually, Aeolian placers (autochthonous and allochthonous) are formed due to deflation of ore sources or gold–bearing reservoirs, and placers of heterogeneous origin are formed by deflation of previously formed coastal-lake placers or as a result of alternating activity of temporary watercourses and Aeolian processes. The presence of pseudo-ore gold in the lacustrine-alluvial deposits suggested the arrival of gold from gold-bearing conglomerates of the Mesozoic age. So, based on the results of mineralogical studies of placer gold and field observations, it has been proved that for the first time isolated Aeolian gold and pseudorudic gold deposits on the territory of Mongolia, at a qualitatively new level of knowledge, make it possible to establish the genesis of the formation of gold-bearing placers, as well as more correctly predict the location of gold sources and select methods for their search.
The maceral composition of borehole coal cores from the Tyumen and Vasyugan Formations in the southeastern West Siberian megabasin (Tomsk and Novosibirsk regions) was determined using reflected light microscopy. We have identified and described the groups, classes, subclasses, types, and subtypes, with the most typical macerals photographed and their percentage shares determined from some samples. The maceral compositions are shown to be largely identical in the studied coals of the Tyumen and Vasyugan Formations. The revealed variations in the maceral groups for these formations are as follows (%): vitrinite - 27-100 (averaging 77); inertinite - 0-73 (18); liptinite - 0-33 (8) for the Tyumen Formation, and vitrinite - 52-100 (averaging 82); inertinite - 0-44 (14); liptinite - 0-48 (12) for the Vasyugan Fm (%), thus suggesting a close similarity in the facies conditions of the formation of their coals. The higher plant inputs — lignocellulose tissues, and more rarely, lipid components — served as their source material. In this regard, Upper and Middle Jurassic coals have been extremely underexplored within this area.Analysis of the maceral composition of coals, along with lithological studies, contribute to understanding the facies conditions of the formation of coal-bearing strata. These data may also be useful for petroleum producers in developing hydrocarbon deposits for efficient underground coal gasification, to alleviate the tight supply of natural gas.
G.A. Palyanova1,2, E.N. Svetova3, T.N. Moroz1, Yu.V. Seretkin1,2, L.Yu. Kryuchkova3 1Sobolev Institute of Geology and Mineralogy, Russian Academy of Sciences, Novosibirsk, Russia 2Novosibirsk State University, Novosibirsk, Russia 3Institute of Geology, Russian Academy of Sciences, Petrozavodsk, Russia 4Saint Petersburg State University, Saint Petersburg, Russia
Keywords: agates; zeolites; Tevinskoye and Kinkilskoye deposits; genesis.
The morphology, species, and chemical composition of zeolites in agates from the Tevinskoye and Kinkilskoye deposits (Western Kamchatka, Russia) were studied in detail for the first time. Optical and scanning electron microscopy, EPMA, X-ray diffraction analysis, Raman spectroscopy, and X-ray computed microtomography were used. High-silica zeolites have been identified: clinoptilolite-Ca, clinoptilolite-Na, heulandite-Na, heulandite-K and mordenite. Agates from the Tevinskoye deposit were identified as intergrowths of orange and colorless prismatic clinoptilolite-Na crystals, forming a continuous rhythm up to 0.5 mm thick at the contact zone between the agate and the host rock. Numerous mordenite spherulites formed by radially radiating fine-acicular crystals approximately 1 mm long and rare intergrowths of prismatic clinoptilolite-Ca, clinoptilolite-Na, heulandite-Na, heulandite-K crystals were also diagnosed at the boundary between the agate and the host rock from the Kinkilskoye deposit. A typomorphic feature of clinoptilolite and heulandite in agates from both deposits is the admixture of BaO (0.22 to 0.73 wt.%). Silica minerals in the agates are represented by low-temperature cristobalite, chalcedony, quartzine, moganite, microgranular and coarse-crystalline quartz, including amethyst. The presence of "immature" forms of silica — moganite and low-temperature cristobalite — in the studied agates is associated with the young (Eocene) geological age of the volcanic formations. The formation of zeolites in the Tevinsky and Kinkilsky agates could have occurred with the participation of thermal neutral or alkaline. Crystallization of zeolites on the walls of gas cavities apparently occurred from supersaturated (Al, Na, K, Ca, Ba) aqueous solutions and preceded the precipitation of silica.
V.V. Pupatenko1,2 1Institute of Tectonics and Geophysics, Far Eastern Branch, Russian Academy of Sciences, Khabarovsk, Russia 2 Pacific National University, Khabarovsk, Russia
Keywords: Low-cost seismic instrument, MEMS accelerometer, low-frequency geophone, passive seismic tomography, earthquake early warning systems, dense seismic networks.
This article provides a review of the current state and prospects of low-cost seismic instruments. These devices enable the solution of a wide range of scientific and applied tasks, while their cost is one or two orders of magnitude lower than that of professional counterparts. The principal types of sensors are examined, including low-frequency geophones and MEMS accelerometers, with a focus on their design features, sensitivity range, and intrinsic noise levels. The typical architecture of recording equipment is described. Examples of the most common low-cost seismic instruments, such as the Raspberry Shake series and the P-Alert system, are provided, along with their technical specifications and application domains. Key application areas are analyzed, including earthquake early warning systems, volcano monitoring, passive seismic tomography using ambient noise records, experiments to measure the full wavefield from weak earthquakes, as well as educational and citizen science projects. The strengths and weaknesses of low-cost instruments are identified, encompassing limitations in recording weak signals and advantages related to network density. Promising future directions are outlined, such as improving measurement accuracy and employing machine learning methods for processing large volumes of data. It is concluded that, when intelligently combined with modern processing algorithms and dense network infrastructure, low-cost seismic instruments are capable of making a significant contribution to earthquake seismology, volcanology, and educational programs.
K.K. Kolesov1, E.F. Letnika1, A.V. Ivanov1, S.I. Shkolnik2, A.A. Zhdanov1 1Sobolev Institute of Geology and Mineralogy, Siberian Branch of the Russian Academy of Sciences, Novosibirsk, Russia 2Institute of the Earth's Crust of the Siberian Branch of the Russian Academy of Sciences, Irkutsk, Russia
Keywords: Tillites, Karatau-Dzhebagli block, Bolshoy Karatau, Kosshokinskaya Formation, Ulutau Series
The definition of glacial deposits (tillites) in Precambrian sections is a difficult task due to the frequent similarity of their composition and structure with other sedimentary rocks. This is due to the fact that Precambrian sediments have been losing their inherent geomorphological and lithological features over their long history. Tillites are important markers of climate change and are widely used in stratigraphic correlations and geodynamic reconstructions. The research in this article is aimed at studying tillites within the Bolshoy Karatau ridge in order to substantiate the composition and age of rocks on the eroded surface during the movement of ancient glacier. The age values of detrital zircons from the tillite matrix form the main intervals of 740-856 million years (32 grains), 1950-2040 million years (14 grains) and 2200-2630 million years (26 grains) with age peaks of 765, 835, 924, 2030 and 2435 Ma. The following ages were obtained for boulders from the tillite horizon: 746±4 million years (9 grains); 778±4 million years (9 grains); 746±3 million years (13 grains); 788±3 million years (16 grains). The obtained dates for boulders from the tillite horizon have similar age analogues within the Middle Tien Shan, Karatau-Talas, Zheltau, Chu-Kendyktas, and Ulutau blocks.
This special issue of the Geology and Geophysics contains articles presented in the wake of the scientific conference "High-Pressure Mineral Formation Processes: The Origin of Diamonds and Mantle Magmas," dedicated to the 90th anniversary of the birth of the outstanding researcher of diamond formation, Academician Nikolai Vladimirovich Sobolev. The conference took place from June 17–19, 2025, in the Novosibirsk Akademgorodok at the V.S. Sobolev Institute of Geology and Mineralogy, Siberian Branch of the Russian Academy of Sciences. The range of topics covered, from detailed studies of crystal structure defects in individual diamonds and inclusions in it to the regimes and timing of plate tectonics on the early Earth, fully reflects N.V. Sobolev's contribution to the formation of modern understanding of the evolution of the Earth's mantle composition and the formation settings of kimberlites and diamonds.
Sobolev A.V.1, Sobolev S.V.2,3
1 Univ. Grenoble Alpes, Univ. Savoie Mont Blanc, CNRS, IRD, Univ. Gustave Eiffel, ISTerre, Grenoble, France.
2 GFZ Helmholtz Center for Geosciences, Potsdam, Germany.
3 University of Potsdam, Institute of Geosciences, Potsdam, Germany.
The main process that changes Earth’s silicate composition after core segregation is the formation and recycling of continental crust. These processes are closely related to the tectonic regimes that operated at different times during Earth’s history. This review combines recent geochemical data and geodynamic models of how continental crust formed throughout Earth’s history, especially during the Hadean and Archean eons. Continental crust cannot form by direct melting of the dry ultramafic mantle. It requires water, mafic protolith, and minerals compatible with high-field-strength elements (Ti, Nb, Ta, Zr, Hf), such as amphibole, rutile, ilmenite, or jadeite pyroxene. For the early Earth, the most likely model involves two stages: first, basaltic or picritic (oceanic) crust is extracted from the mantle, leaving behind a refractory harzburgitic residue. Then, after hydration, the oceanic crust subducts, melts or releases water to flux melting in the mantle, creating continental-crust magmas. Meanwhile, the remaining refractory residue mixes with refractory mantle material, producing a depleted mantle reservoir. Canonical Nb/U and Ce/Pb ratios are unaffected by mantle melting under dry conditions but change during melt generation when amphibole and high-Ti phases are present. Therefore, these ratios are useful indicators of continental crust formation. Geochemical tracers such as (1) Sr isotope compositions of komatiite melts and plagioclase in anorthosites, (2) element ratios in komatiite melts, (3) trace element contents and Hf isotopic compositions of zircon, and (4) decay products of short-lived Sm and Hf isotopes in rocks either support or do not contradict the operation of active continental crust formation and mantle depletion during the Hadean. Production and recycling of continental crust in this period likely involved episodic, short-lived subduction triggered by plumes. Overall, these findings suggest that tectonic regimes in the Hadean (4.4-4.0 Ga after magma-ocean solidification) and in the Eoarchean (4-3.6 Ga) were more dynamic and varied in time and space than previously thought. However, the development of global plate tectonics—requiring a connected network of subduction zones, mid-ocean ridges, and transform faults—could only start later, during the Archean. The causes of the onset of plate tectonics throughout Earth’s history are still debated, and new ideas (such as those involving surface processes, such as the erosion of continents) are being proposed and require further testing.
G.V. Gurin1, I.A. Panteev2
VIRG-Rudgeofizika Ltd, St. Petersburg, Russia
Keywords: mathematical modeling, 3D inversion, deep electrical resistivity tomography
Electrical resistivity tomography (ERT) has numerous applications. The high demand for ERT is stimulating the active development of equipment and technologies, as well as methods for analyzing, processing, and inversion of ERT data. The use of 3D electrode arrays for surveying complex geoelectrical environments is increasing due to the limitations and shortcomings of 2D electrode arrays. 3D electrode arrays often allow for increased spatial resolution and reliability in the inverted models. The advantages of 3D electrode arrays over 2D electrode arrays for ERT surveying often not obvious. Geophysicists often decline the use of 3D electrode arrays for this reason. This paper reviews ERT technologies that use 3D electrode arrays, methods for building of geoelectric models, their advantages and disadvantages. Based on mathematical modeling/inversion of ERT data, the advantages of 3D electrode arrays and the disadvantages of 2D electrode arrays are demonstrated. We conducted analyses of typical distortions in models and systematized them. We presented a simple 3D electrode array optimized for labor and cost, with current and potential electrodes located on adjacent profiles. We showed that models inverted by ERT data with 3D optimized electrode arrays do not have the distortions typical 2D electrode arrays. Thus, using 3D optimized electrode arrays, labor and cost can be reduced for field work without losing the spatial resolution of models inverted by ERT data. This opens the way for active use of the ERT with 3D electrode arrays to explore ore deposits.
RESULTS OF TRIAL MAGNITOVARIATIONAL SOUNDING IN THE KAMCHATKA VOLCANIC REGION 1V.I. Il’ichev Pacific Octanological Institute Far Eastern Branch Russian Academy of Science, Vladivosrtok, Russia 2Institute of cosmophysical research and radio wave propagation FEB RAS, Paratunka, Russia
Keywords: magnetovariational sounding, tipper, ModEM, 3D inversion, geoelectrical section
The results of performance the magnetovariational sounding in geologically complex Eastern Kamchatka volcanic belt with the active at present time volcanoes are presented. In investigation the geomagnetic variations received at “Paratunka” observatory and its station “Karymshina”, which is about 18 km apart to southwest from it. Calculated at both site tippers were undergone to 3D inversion by means of ModEM program. During inversion the different start models as homogeneous half-space and the same including the water layer of the nearest Pacific Ocean, taken into account its bathymetry, were used. The carried out inversion let to define the conductive blocks in geoelectrical section at depth range about 10-50 km under volcanic belt. In order to test this result, the 3D inversion of tippers taken by means of solving the direct magnetotelluric task for model containing conductive blocks in the same depth range was performed. In the article the most characteristic horizontal slices and vertical sections of received evaluative geoelectrical model of study area, including Paratunka geothermal area and caldera Karymshina, are presented. The results obtained are compared with the results of a seismic tomography at S-waves, which were get in this region.
A.G. Konstantinov
Trofimuk Institute of Petroleum Geology and Geophysics of Siberian Branch Russian Academy of Sciences (IPGG SB RAS) Novosibirsk, Russia
Keywords: ammonoids, Carnian Age, paleobiogeography, Boreal Realm.
The taxonomic composition and distribution of Boreal Carnian ammonoids from northeastern Asia and Arctic Canada have been clarified, the generic assignment of some species has been revised, and their definitions have been standardized. A qualitative comparative analysis of ammonoid assemblages from northeastern Asia and the Canadian Arctic Archipelago has been conducted for the omkutchanicum, armiger, pentastichus, and combined yakutensis and bytschkovi phases. The presence of ammonoids of the genus Boreotrachyceras in the early Carnian of Arctic Canada has been substantiated. This has allowed for the first comparison of coeval ammonoid assemblages of the omkutchanicum phase from northeastern Asia and Arctic Canada, demonstrating the commonality of the ammonoid generic composition of this time throughout the Boreal Realm. It has been established that the early Carnian ammonoid fauna of northeastern Asia differs from that of Arctic Canada by the presence of Tethyan genera (Trachyceras, Striatosirenites) and families (Arpaditidae). A comparative analysis of the ammonoid fauna of the late Carnian has been conducted for the first time, separately for the formation time of the Arctosirenites canadensis beds, equivalent to the pentastichus phase, and for the formation time of the Jovites borealis beds, equivalent to the yakutensis and bytschkovi phases. As a result, for the first time, with phase accuracy, the time of penetration of Tethyan genera into the paleobasins of the Yukon and Arctic Canada (the time of formation of layers with Jovites borealis) was determined, and the belonging of Arctic Canada to the Tethyan Realm was substantiated.
K. G. Parkhacheva, S. K. Kuznetsov, M. Yu. Sokerin, N. V. Sokerina
Keywords: Sulphide mineralization, gold bearing capacity, Middle Timan, isotope, mineral formation conditions
Zones of hydrothermal vein-disseminated, disseminated sulfide, predominantly pyrite, mineralization in Riphean rocks of the Kyvvozhsky region are characterized by elevated contents of Au, Cu, Se, Mo, Ag, Pb, Bi, Sb, Zn. According to the results of the correlation analysis, the following groups of ore elements were identified, within which the strongest positive correlations were established: Ag-Bi-As-Со; Pb-Cu-Zn-Se; Co-Ni-As. Pyrite, arsenopyrite, chalcopyrite, galena, sphalerite, cobaltite, monazite, xenotime, bornite, and covellite are found in association with pyrite in sulfide veinlets. Native gold is rare; particles with peripheral low-grade zones alternate with high-grade gold overgrowths are present. Inclusions of pyrite, pentlandite, monazite, and albite are observed. The gold contains Ag, and sometimes Cu and Pd, as impurities. Judging by the relationships between the minerals, pyrite was the earliest, followed by pyrrhotite, chalcopyrite, and cobaltite, followed by sphalerite, galena, and gold. The formation of sulfide mineralization is associated with hydrothermal processes that occurred in pre-Middle Devonian times, associated with the activation of tectonic-magmatic processes. Geological data, the heavy isotopic composition of pyrite sulfur with a variation in δ34S values from +15.8 to +23.6 ‰, suggest that the most important role was played by regional metamorphic processes that facilitated the mobilization and migration of hydrothermal solutions along faults with the borrowing of various components from the host rocks and subsequent crystallization of sulfides and gold. In some cases, the presence of Cu and Pd impurities in gold indicates a possible influence on the mineral-forming solutions of basic rocks or their partial depth nature as derivatives of basite-hyperbasite magmatism. The Kyvvozhsky district is of interest for primary gold deposits and merits continued exploration.
O.A. Gulevich, L.B. Volkomirskaya
Pushkov Institute of Terrestrial Magnetism, Ionosphere and Radio Wave Propagation, Russian Academy of Sciences,
Moscow, Russia
Keywords: GPR, amplitude-frequency analysis, deep GPR, electromagnetic CDP, amplitude-frequency characteristics, AFC
This study analyzes the amplitude-frequency characteristics (AFC) of deep GPR data gathered using variable offsets within the permafrost of the Nadym District, Yamalo-Nenets Autonomous Okrug. The initial frequency response of the raw data, which underwent only basic pre-processing, is presented, evaluating the effects of transmitter-receiver separation (100–750 m) as well as the spatial and depth-based placement of the analysis zone. This approach reveals the spectral evolution of electromagnetic signals within the geological environment during the late stages of the process. Results indicate that as the distance from the source increases, the signal undergoes standard attenuation, alongside three primary spectral effects: a downward frequency shift of the peak amplitude, a narrowing of the spectral bandwidth, and a significant rise in low-frequency components—the latter being primarily attributed to zero-line drift. Adopting spectral analysis techniques from seismic exploration for deep GPR data is a promising way to refine data processing and improve subsurface interpretation.
S.V. Krivovichev1,2,@, A.S. Osipov1, M.S. Avdontseva2, J.H. Chen3, G.O. Samburov1, O.F. Goychuk1, I.V. Pekov4, T.L. Panikorovskii1,2, Y.Q. Li3 1 Nanomaterials Research Centre, Kola Science Center, Russian Academy of Sciences, Apatity, Russia 2 Department of Crystallography, Institute of Earth Sciences, St. Petersburg State University, St. Petersburg, Russia;
3 School of Resources, Environment and Materials, Guangxi University, Nanning China
4 Faculty of Geology, Moscow State University, Moscow, Russia)
Keywords: sobolevite, crystal structure, antiperovskite, density functional theory, Kola peninsula, Arctic
Sobolevite with low Mn content from the Karnasurt deposit (Lovozero, Kola peninsula) has been characterized by electron microprobe analysis, single-crystal structure refinement, high-temperature X-ray diffraction and density functional theory (DFT) calculations. The chemical formula can be written as Na7.04(Ca0.87Mg0.16)S=1.03(Ti1.48Zr0.20Mn2+0.18 Nb0.10Fe2+0.06)S=2.02Si2.05P2.02O17.12F0.88. The crystal structure refined to R1 = 0.037 (P21/c, a = 7.0908(3), b = 5.4108(2), c = 40.6179(19) Å, b = 93.095(4)o, V = 1556.11(11) Å3) is based upon the [Ti2O2[Si2O7](PO4)]5-
titanosilicate-phosphate HOH layers (TS blocks). The interlayer space is occupied by the AC complex formed by Na+, Ca2+
and Mg2+ cations along with (P1O4)3- groups and F- anions. The F- anions are coordinated octahedrally by Na and Ca to form antiperovskite [FA3] chains (A = Ca, Na) running parallel to the b axis. The crystal chemical formula of sobolevite is (Na6.92Ca0.92Mg0.16)S=2.00(Ti1.46Zr0.18Mn2+0.15Nb0.15Fe2+0.06)S=2.00(Si2O7)(PO4)(F0.81O0.19)S=1.00, which corresponds to the idealized formula Na7CaTi2O2[Si2O7](PO4)2F and allows to consider it as a polymorph of quadruphite. The relations between sobolevite and quadruphite are pseudo-polytypic. The thermal behavior of sobolevite is typical for layered structures corrected by shear deformations. According to DFT calculations, sobolevite exhibits p-type semiconductor behavior with a band gap of approximately 2.75 eV. Altering the Ti/Nb ratio influences the band structure, inducing magnetism in the crystal and transforming it from a semiconductor to a semimetal or even a metal. The material exhibits strong absorption in the ultraviolet region, with an absorption coefficient reaching up to 2×105 cm-1. The overall structural architecture of sobolevite combines features of both titanosilicates and antiperovskite-type structures, which makes it an interesting example of hybrid structures with potentially interesting functional properties.
N.N. Nevedrova1, Z.Y. Kuzina1, A.M. Sanchaa1, E.V. Balkov1 1Trofimuk Institute of Petroleum Geology and Geophysics, Siberian Branch of the Russian Academy of Sciences, Novosibirsk, Russia
Keywords: Electrical tomography, numerical modeling, three-dimensional inversion, data verification, quantitative analysis
The article presents a methodology for quantitative verification of three-dimensional geoelectric models constructed from electrical tomography (ET) data in complex geological conditions. As an example of real data, a set of measurements is considered in the fault zone of the southeastern boundary of the Gorlovka depression (Novosibirsk region), where an increase in seismic activity has been observed in recent years. It is probably caused by the development of large coal mines. The relevance of the work is due to the interpretative ambiguity of ET data in heterogeneous geological environments and the appearance of artifacts in inversion models, which can subsequently lead to false interpretation of the results. It is proposed to move from the traditional visual comparison of the results of inversion of field and synthetic data to quantitative analysis. For this purpose, the ERT_Comp software tool has been developed, which calculates the relative difference between the model and field values of apparent resistivity at specific spacings. The use of the technique for field data from three parallel profiles made it possible to quantitatively substantiate the choice of the optimal 3D geoelectric model reflecting the presence of a subvertical fault zone. The proposed approach does not completely remove ambiguity, but significantly increases the reliability of interpretation. Prospects for the work involve the use of gradient models and the establishment of standardized threshold values of relative deviations to select the best interpretive model.
Popov M.S.1, Borisov D.G.1, Levchenko O.V.1, Frey D.I.1,2, Ivanova E.V.1 1Shirshov Institute оf Oceanology, Russian Academy of Sciences, Moscow, Russia
2Marine Hydrophysical Institute
2Russian Academy of Sciences, Russian Academy of Sciences, Sevastopol, Russia
Keywords: sub-bottom profiling, sediment, seismic facies, echo-facies
The Romanche Fracture Zone plays a crucial role in the distribution of Antarctic Bottom Water between the western and eastern Atlantic. However, the influence of bottom currents and other processes on the sediment infilling of the Romanche valley remains understudied. A large set of high-resolution sub-bottom profiling data was used in this work to solve this issue. The interpretation of the results was supported by numerical modeling of bottom current velocities using an ocean circulation model. The first comprehensive map of echo character distribution along the entire transform valley was built, revealing detailed sediment distribution patterns. The study assessed the modern and past influence of bottom currents on sedimentation and identified areas of intense gravity flow activity. The results highlight the Romanche valley as a promising area for studying the history of water exchange between the western and eastern Atlantic.
A. S. Salnikov1, V. S. Seleznev2, P. V. Gromyko2, V.M. Soloviev3, Y. I. Kolesnikov1 1 Trofimuk Institute of Petroleum Geology and Geophysics of Siberian Branch Russian Academy of Sciences, Novosibirsk, Russia.
2 Seismological Branch of the Geophysical Survey of Russian Academy of Sciences
3 Altai‐Sayan Branch of the Geophysical Survey of Russian Academy of Sciences
Keywords: coal seams, discontinuous disturbances, seismic exploration, refracted and reflected waves
Profitability, efficiency, and safety in the
coal mining industry depend on the mining and geological conditions. Quite
often, the geological forecast is not confirmed, especially in the presence of
small-amplitude tectonic disturbances and local geological inhomogeneities,
which is why the development and application of geophysical methods, including
various types of seismic exploration, is of great importance. The article
presents the results of ground-based seismic surveys at the Chulmakan coal
deposit in the Sakha Republic (Yakutia) to clarify the general geological
structure of the study area, identify thin coal layers, study their structure,
and detect tectonic faults. It has been shown that, due to fundamental physical
and technological limitations, the reflected wave method cannot be the only
source of reliable information when studying fine-structured objects. Based on
the joint interpretation of reflected and refracted waves, as well as the
analysis of well data, the authors have successfully traced and refined the
parameters of the thin coal layers, and identified several tectonic faults that
were not detected by drilling. It is also shown that the purposeful development
of methodology, technical means, and technologies for interpreting refracted
waves is not just an academic interest, but an urgent production necessity.
E.S. Persikov1, P.G. Bukhtiyarov1, A.G. Sokol2, A.N. Kruk2, D.M. Sultanov1. 1Institute of Experimental Mineralogy RAS, Chernogolovka, Russia
2V. S. Sobolev Institute of Geology and Mineralogy Siberian Branch Russian Academy of Sciences
(IGM SB RAS), Novosibirsk, Russia
Keywords: viscosity, structure, basalt, model kimberlite and ultramafic melts, temperature, pressure, upper mantle, model
We obtained the experimental and theoretical data on the temperature and pressure dependencies of the viscosity of model ultramafic and basalt melts at mantle thermodynamic parameters. Based on systematic experimental and theoretical studies, we established generalized patterns of the temperature and pressure dependencies of the viscosity of depolymerized magmatic melts (basaltic, model ultramafic and kimberlite) under conditions of the upper mantle. We have established an anomalous and extreme dependence of the viscosity of basaltic melts on pressure: as the pressure increases, the viscosity of such melts decreases, passes through a minimum, and then increases again. In contrast, for depolymerized ultramafic melts, the dependence of their viscosity on pressure corresponds to the theoretical dependence, i.e., as the pressure increases, the viscosity of such melts increases exponentially. A structural - chemical model has been developed for reliable predictions and calculations of the viscosity of magmatic melts in the full range of their basicity, from acidic to ultramafic, at T, P - parameters of the Earth's crust and upper mantle, with an error comparable to the experimental error. Using a computer version of this model, the characteristic features of the change in viscosity of ultramafic and basalt melts as they rise from the mantle to the Earth's crust have been established.
An approach is proposed for assessing the distribution of industrial minerals in the upper part of the geological section based on reprocessing and interpretation of archived 3D seismic data. The approach includes reconstruction of P- and S-wave velocity models using modified refraction and surface wave methods, automated extraction of dispersion curves using a neural network algorithm, as well as calculation and integration of a set of seismic and morphometric attributes. Based on the combined feature space, clustering is performed to delineate facies associated with deposits of different genesis. The approach was tested on the Kharampur license area located in the Arctic zone of West Siberia, characterized by the presence of permafrost. For this site (area ~60 km²), it is shown that the proposed workflow enables the construction of detailed predictive maps consistent with drilling data and active quarries. Clustering based on combined seismic and terrain-related features allowed identification of facies and the construction of physico-geological models of sand and peat bodies with economically significant thicknesses. This approach enables the generation of high-resolution predictive maps without additional field surveys, with a resolution comparable to engineering-scale drilling data.
This paper presents the results of studies of zircon grains from kimberlite and carbonatite bodies, as well as from ancient and modern diamond placers of the Lena–Anabar subprovince of the Siberian Diamond Province. The research includes U–Pb zircon dating and the determination of trace and rare earth element concentrations using the SHRIMP-IIe secondary ion mass spectrometer. The study covered kimberlite primary bodies of different ages, Late Jurassic carbonatite breccias, all diamond placers of the Anabar, Kuonamka, and Prilensky regions, as well as placer occurrences in the Primorsky, Lower Olenek, Middle Olenek, Muno-Tyung, and Daldyn-Alakit diamondiferous regions. In association with diamonds, zircon grains yielded Jurassic, Triassic, Permian, Late Devonian-Early Carboniferous, and Silurian-Early Devonian ages, which are consistent with the ages of known primary sources. New data indicate a broader age range of Triassic productive volcanism. Analysis of all diamond placers showed that approximately 79% of them were formed from Triassic primary sources.
E.F. Sinyakova1, D.A. Ulybin1,2,3, K.A. Kokh1 1V.S. Sobolev Institute of Geology and Mineralogy, Siberian Branch of the Russian Academy of Sciences, Novosibirsk, Russia
2Nikolaev Institute of Inorganic Chemistry, Siberian Branch of the Russian Academy of Sciences,
Novosibirsk, Russia
3Novosibirsk State University, Novosibirsk, Russia
The article presents the results obtained during the crystallization of a melt with the compositionin (in at. %): 14.0 Cu, 30.0 Fe, 4.0 Ni, 51.1 S, 0.1 each of Pt, Pd, Ag, Au, As, Bi, Pb, Se and Sn, in wt. %: 19.5 Cu, 36.7 Fe, 5.1 Ni, 35.8 S, 0.4 Pt, 0.2 Pd, 0.2 Ag, 0.4 Au, 0.2 As,0.5 Bi, 0.5 Pb, 0.2 Se and 0.3 Sn under isothermal conditions and with directional crystallization. Under gradient-free conditions, a homogeneous crystalline massif consisting of a mixture of monosulfide and intermediate solid solutions crystallizes from the melt. When cooled to room temperature, the monosulfide solid solution forms the pyrrhotite structure 1C, 3C, and the intermediate solid solution decomposes into a fine-grained mixture of isocubanite and chalcopyrite. Using the Bridgman-Stockbarger method, a three-zone ingot was obtained with the following sequence of phase crystallization from the melt: Mss / Iss1 / Iss2 and secondary zoning: chalcopyrite + pyrrhotite 1C, 3C + isocubanite (zone I) / chalcopyrite + low-temperature intermediate solid solution + Fe-pentlandite, sugakiite (zone II) / chalcopyrite + Ni-pentlandite + millerite + bornite (zone III). The specific influence of As, Bi, Pb, Se and Sn impurities on the behavior of Pt, Pd, Ag and Au under different crystallization conditions was revealed. In both experiments, solid solutions play a minor role in their concentration. The main amount of these impurities is released in the form of independent phases. The main role in their formation is played of immiscibility of the parent sulfide melt, resulting in the formation of a sulfide-metalloid melt, Ls-m, which concentrates impurities of Pt, Pd, Ag, Au, and chalcophile elements. The data on the directionally crystallized sample indicate a more complex process of immiscibility of the initial melt compared to its immiscibility during volumetric crystallization, namely 1) the simultaneous release of two types of liquids during cooling of the initial sulfide melt in zone II: one of these liquids is formed in the (Pd, Au)-(As, Bi) subsystem, and the second in the (Pt, Pd)-Pb-(S, Bi, As) subsystem; 2) in zone III, secondary immiscibility and phase formation processes may occur within the Ls-m droplets during cooling; 3) сoncentration of microphases at the end of the ingot in zone III.
N.S. Tychkov1, A.M. Dymshits2,3, E.A. Muraveva1, A.M. Logvinova1, N.P. Pokhilenko1,4 1Sobolev Institute of Geology and Mineralogy, Siberian Branch of the Russian Academy of Sciences, Novosibirsk, Russia (tych@igm.nsc.ru)
2Institute of the Earth’s Crust, Siberian Branch of the Russian Academy of Sciences, Irkutsk, Russia 3Geological Institute KSC RAS, Apatity,Russia
4Geology and Geophysics Department of Novosibirsk State University, Novosibirsk, Russia
Keywords: Siberian platform, kimberlite, clinopyroxene, geotherm, lithosphere, diamond
As a result of data processing for more than 3000 clinopyroxene xenocrysts from kimberlites of different ages in the Siberian Platform, a generalized model of the lithospheric mantle thickness evolution within the Yakutian diamond province has been obtained. New data on surface heat flow (SHF) and thermal lithospheric thickness (TLT) have been obtained for seven localities on the Siberian Platform, including Paleozoic and Mesozoic kimberlites from different regions with different diamond potential, as well as Late Triassic sedimentary rocks from the northeastern margin of the platform. The composition of clinopyroxenes from the Late Triassic sedimentary rocks corresponds to the Devonian–Carboniferous type of lithospheric mantle of the Siberian Platform. New data on kimberlites from the northeastern part of the platform (Ivushka and Zaoblachnaya pipes) yield results that contradict previous interpretations. The Ivushka pipe (Toluopka field) exhibits a TLT thickness closer to that of Jurassic kimberlites, but the sampling depth of clinopyroxene-bearing rocks is typical of Devonian–Carboniferous kimberlites. The geotherm of the Zaoblachnaya pipe (Khorbusuon field) corresponds to Devonian–Carboniferous and Triassic kimberlites, which contradicts the absence of diamonds in the pipe and its tectonic setting. The SHF and TLT values separating the Jurassic lithosphere of the northeastern part of the platform from the older lithosphere are 36.9 mW/m² and 230 km, respectively. Based on the TLT and the depth of lithospheric section sampled by kimberlite magmas of different ages, it is shown that the lower diamond potential of Triassic kimberlites may be related not to lithospheric thinning, but to a shallower depth of onset of mantle material entrainment, caused by increased permeability of the lithospheric mantle resulting from the preceding influence of the Permo–Triassic plume.
O.M. Turkina
Sobolev Institute of Geology and Mineralogy, SB RAS, Novosibirsk, Russia
Novosibirsk State University, Novosibirsk, Russia
Keywords: Dolerite, Proterozoic, geochemical indicator, southern flank of Siberian craton, magma source
This paper presents an analysis of compositional data on Proterozoic dolerites from dikes and sills on the southern flank of the Siberian Craton, formed in an intracontinental setting between 1.91 and 0.72 Ga. Indicator geochemical parameters have been established for four age groups of dolerites, reflecting differences in their of mantle sources and the conditions of generation of the initial melts. Neoproterozoic dolerites of the Nersa complex are characterized by lowest (Sm/Yb)n and (Nb/Y)pm
ratios and were formed with the contribution from enriched subduction-modified lithospheric mantle (SZLM) and a depleted (asthenospheric) source. Dolerites aged 1.35 Ga are distinguished by the maximum concentrations of incompatible rare elements and high (Sm/Yb)n and (Nb/Y)pm values, their formation occurred from an enriched plume mantle source. Mesoproterozoic (~1.6 Ga) dolerites of the Prisayan Trough are characterized by elevated contents of TiO2 and high-field strength (Nb, Ta) elements compared to dolerites of the Nersa Complex. They are dominated by an enriched plume source with high (Nb/Y)pm and TiO2/Yb ratios, with limited contribution from SZLM. Paleoproterozoic (1.91 Ga) dolerites, while similar in (Sm/Yb)n values to Neoproterozoic ones, have lower (Nb/Y)pm
and (Nb/La)pm ratios, indicating a more depleted mantle source. The proposed diagrams (Sm/Yb)n – (Nb/Y)pm and (Nb/La)pm
– (Nb/Y)pm allow us to systematize dolerites from the dike swarms of the southern flank of the Siberian craton based on the similarity in composition with dolerites of four stages of Proterozoic basic magmatism.
Several thermocirques have been detected in the Oymyakon Upland, in the basin of the upper reaches of the Indigirka River, based on space imagery. Two of these thermocirques were studied in the Suntar River valley. The thermocirqures formed in 2014-2016 after an increase in precipitation, and they continued to grow at a rate of 5-35 m/year until 2023-2024. Currently, they are 130-220 m long. The thermocirques were formed on the slope of a terminal moraine hill at an absolute height of approximately 900 m. The moraine deposits exposed in the back wall of the larger thermocirques consist of clastic material ranging from gravel to large boulders and blocks with a sandy-loamy fill. Two cryofacies were identified in the upper 5 m of the section based on their cryogenic structure: the lower cryofacies is an initially frozen moraine with a primary cryogenic structure, while the upper cryofacies is a taberated deposit of the lower cryofacies that has been re-frozen. Epigenetic ice wedges up to 2.5-3 m wide penetrate from the contact between the cryofacies, forming polygons with a size of approximately 30 m. It is assumed that the terminal moraine was formed during the first cryochron of the Late Pleistocene and is stratigraphically associated with the Yugler horizon, while partial thawing occurred in the first half of the Holocene.
D.A. Bushnev1, N.V. Nosova2, N.S. Burdelnaya1, S.A. Ondar3 1 Institute of Geology of Komi Scientific Center of the Ural Branch of the Russian Academy of Sciences, Syktyvkar, Russia 2 Komarov Botanical Institute of the Russian Academy of Sciences, Saint Petersburg, Russia
3 Tuvinian Institute for Exploration of Natural Resources of the Siberian Branch of the Russian Academy of Sciences, Kyzyl, Russia
Keywords: Jurassic plants, Leptostrobales, chemotaxonomy, diaromatic secobicadinane, n-C33n-C35 alkanes, plant biomarkers
Samples of Jurassic coal-bearing rocks from the Ulug-Khem Coal Basin (Republic of Tyva, Russia) and from the Angren coal mine (Uzbekistan) were investigated. These rocks contain numerous leaf remains of leptostrobaleans. The material from Angren is represented by a mass of numerous leaf fragments of Phoenicopsis taschkessiensis and Czekanowskia eugeniae (Leptostrobales) forming the leaf litter. The hydrocarbon composition of the rock extracts was studied. All the samples showed high concentrations of C33 and C35 n‑alkanes. The rock extract contains high concentrations of abietic acid derivatives such as dehydroabietanes, simonellite, retene, and norisopimarane indicating a relationship between leptostrobaleans and conifers by their biochemistry. Retene was found in a more mature sample from Tyva, containing abundant leaf remains of Czekanowskia tuvensis. The extract of a rock sample from Tyva contains aromatic secobicadinans, which are the major components of the aromatic fraction. Their connection with leptostrobaleans was excluded based on comparison with samples from Angren; however, their botanical affiliation is not obvious. The discovery of polycadinene resin derivatives in the Middle Jurassic material from Tyva indicates that they were probably produced by some groups of Jurassic plants.
G.P. Shironosova1, V.O. Goryunova1,2, I.R. Prokopyev1,2,3 1V.S. Sobolev Institute of Geology and Mineralogy, Siberian Branch of the Russian Academy of Sciences,
Novosibirsk, Russia
2Novosibirsk State University, Novosibirsk, Russia
3Tuvinian Institute for Exploration of Natural Resources of Siberian Branch of the Russian Academy of Sciences, Kyzyl, Russia
Keywords: REE, monazite, xenotime, bastnaesite, parisite, REE-fluorite, REE-fluorapatite, thermodynamic modeling.
Thermodynamic calculations were carried out to model the process of interaction between fluid with different concentrations of fluorine and the mineral association calcite + monazite (in the presence of barite and celestine), in order to establish how fluorine concentrations in the fluid change the initial mineral association and the forms of REE concentration during the formation of carbonatite complexes. Thermodynamic calculations were carried out at temperatures of 500, 400, 300, 200 and 100°C and pressures of 2000, 1000, 500, 250 and 125 bar in the range of fluorine concentrations of 10-4
– 1 mol/kg H2O. It has been established that when monazite and calcite are exposed to an acidic (pH 3) fluoride-carbonate-chloride solution, increasing fluorine concentrations result in the formation of REE-containing fluorapatite, fluorite, and the fluorocarbonates – bastnasite and parisite. Fluorocarbonates begin to form in equilibrium with decreasing temperature, beginning with decreasing fluorine concentrations in the initial solution. Formation of parisite, according to the generalized formula CaLn2(CO3)3F2, requires twice as much fluorine as that for bastnaesite LnCO3F, and under acidic conditions, it appears only at 200 and 100°C in the range of 0.01–0.1 m HF. At the highest concentration considered (1 m HF), REE-fluorapatite, along with parisite, also disappears from the equilibrium assemblage due to the maximum possible amount of the third calcium consumer, REE-containing fluorite. Lowering the temperature increases the stability of REE-fluorite by reducing the fluorine concentration required for its formation in the fluid. With increasing pH of the ore-forming environment, the formation of parisite at 200°C is observed even at low HF concentrations (0.0001 m), replacing bastnaesite under these conditions. Increasing pH is also accompanied by increased stability of REE fluorite and the appearance of strontium-bearing calcite and hydroxyapatite in fluorine-poor fluids. In an acidic fluoride-carbonate-chloride solution, after its interaction with the monazite+calcite assemblage, the total concentration of lanthanides (Ln
tot) decreases with decreasing temperature. Starting at 400°C, the Ln
tot curve exhibits a complex dependence on the initial HF concentration and reaches its minimum at maximum m HF. The main contribution to Ln tot
comes from the chloro- (at low m HF) and fluoro- (starting at 0.01 m HF with decreasing temperature) complexes of light REEs. The contribution of heavy REEs is approximately three orders of magnitude lower than that of light REEs.
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