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Volume 523, Nº 2 (2025)
- Ano: 2025
- ##issue.datePublished##: 15.08.2025
- Artigos: 20
- URL: https://journals.rcsi.science/2686-7397/issue/view/23981
GEOLOGY
MESOPROTEROZOIC AGE OF PHONOLITHES OF THE MARA VOLCANIC FIELD, BIRYUSINSKOE PRISAYAN’E: Pb–Pb STEPWISE LEACHING METHOD
Resumo
For the first time, the Pb–Pb age of phonolites from the Mar volcanic field located within the Uvat uplift of the Biryusa ledge of the Siberian craton has been determined. A direct estimate of the age of volcanic rocks was obtained using the stepwise leaching method for the whole rock. The obtained age of phonolites, equal to 1513±11 million years, determines the time of activation of alkaline volcanism associated with the extension of the continental crust within the Biryusa protrusion. The Mesoproterozoic age of alkaline volcanism on the southwestern margin of the Siberian craton coincides with the stage of the formation of the Kuonamskaya igneous province on the Anabar shield on the northeastern margin of the Siberian craton.
Doklady Earth Sciences. 2025;523(2):189-196
189-196
LITHOLOGY
Lithological Composition of Bottom Sediments in the Area of Fluid Discharge in the Kara Sea
Resumo
The paper presents the results of lithological and geochemical analysis of marine sediments collected in the southwestern part of the Kara shelf in the area of development of gas-saturated deposits in a paleovalley at a depth of 112 m. It has been established that the accumulation of sediments occurred under conditions of seabed fluid flow as a result of degradation of permafrost and destruction of gas hydrates contained in it, which are apparently suppliers of isotopically heavy waters to the studied strata.
Doklady Earth Sciences. 2025;523(2):197-203
197-203
GEOLOGY OF ORE DEPOSITS
EARLY PERMIAN AGE OF INTRUSIONS AT THE INGICHKE AND MELIKSU TUNGSTEN-POLYMETALLIC DEPOSITS IN THE SOUTHERN TIEN SHAN: FIRST ISOTOPIC U–Pb DATA ON ZIRCON (LA-ICP-MS METHOD) FROM THE INTRUSIVE ROCKS OF THE ZIRABULAK PLUTON (UZBEKISTAN) AND MELIKSU STOCK (KYRGYZSTAN)
Resumo
The paper presents the first data on the isotopic U–Pb dating of zircon (LA-ICP-MS method) form the intrusive rocks of the large Zirabulak granitoid pluton (Uzbekistan), which the Ingichke, the largest one in the Central Asia (about 100 Kt WO3), and the Meliksu tungsten-polymetallic skarn deposits are associated with. These deposits, together with other deposits of tungsten, gold and other metals are part of the largest gold-tungsten metallogenic belt of Tien Shan. They are represented by bodies of hydrothermally-altered skarn with scheelite and sulfides (pyrrhotite, chalcopyrite), and subsequent within- and near-intrusion stockworks of late post-skarn metasomatites (propylitic and phyllic alteration) with polymetallic-scheelite mineralization. The concordant isotopic U–Pb zircon age dates of zircon from rocks of the Zirabulak pluton (289±3.8 Ma for granodiorite of the main intrusive phase and 288±3.3 Ma for granite) and the Meliksu stock (285.8±2.5 Ma and 283±2 Ma for granodiorite of the main intrusive phase) were obtained; they indicate the intrusion emplacement in the Early Permian. This is significantly younger than the known dates (some 300–310 Ma) of granodiorites but is coincident with the dates of granites in the other monzodiorite-granodiorite-granite intrusive massifs of the region, which the significantly smaller tungsten but locally large gold (with subordinate tungsten) deposits (Jilau, Yakhton, Kabuty) are associated with. Such age and metallogenic peculiarities of the productive intrusions can be correlated to the specific features of the geodynamic evolution of the region in the Late Carboniferous-Early Permian.
Doklady Earth Sciences. 2025;523(2):204-216
204-216
GEOCHEMISTRY
DYNAMICS OF METHANE FLOWS FROM GLADKOVSKY AND OLDENBURGSKY MUD VOLCANOES (CRIMEAN-CAUCASIAN REGION)
Resumo
Mud volcanoes are a source of greenhouse gas emissions into the atmosphere. We carried out gas-geochemical monitoring at the Gladkovsky and Oldenburgsky's mud volcanoes for the first time. It was found that the flow rate of mud volcanic gases from salses is much more variable than their chemical composition. In various salses of the same volcano, the chemical composition of mud volcanic gases has significant differences. The measured CH4 flow from macroseeps (salses) is 0.5±0.1 and 2.84±0.32 t/year for Gladkovsky and Oldenburgsky's volcanoes, respectively. The theoretical estimate of CH4 total flow (from mini- and macroseeps) is about 5 and 6 t/year for Gladkovsky and Oldenburgsky's volcanoes, respectively. The Bernard's coefficient for mud volcanic gases shown to be inversely correlated to their emission rate.
Doklady Earth Sciences. 2025;523(2):217-225
217-225
CARBON ISOTOPE COMPOSITION AND RAMAN GEOTHERMOMETRY OF GRAPHITE FROM THE PESTPAKSHA DEPOSIT (KOLA REGION): CONDITIONS OF ORE MINERALIZATION
Resumo
A comprehensive study of graphite from the Pestpaksha deposit (Lapland Granulite Belt, Kola Region) has been conducted, including Raman-based temperature determination and carbon isotopic characterization. C and O isotopic compositions of carbonates from rocks adjacent to graphite ores have also been studied. The structural control of the graphite mineralisation indicates that it was crystallised from the fluid phase. The crystallization of graphite was found to have taken place at a temperature of about 600°C at the retrograde stage of the metamorphic event. Large variations in carbon isotopic composition (δ13CV-PDB from –18.5‰ to –29.0‰) can be explained either by the mechanism of Rayleigh depletion of C-O-H fluid with a high CO2 fraction in a closed system relative to this fluid, or by mixing of carbon from two isotopically contrasting sources. These sources may be the 13C-poor methane-bearing fluids produced during degassing of metamorphic rocks and the anomalously enriched 13C carbonates (δ13CV-PDB ~ +14‰) observed in this study, which are similar in isotopic characteristics to carbonate rocks of the Lomagundi-Jatulian event. In the Rayleigh depletion model, these specific rocks are considered to be the product of crystallization of the residual fluid. Irrespective of the formation model adopted, the available evidence suggests that Pestpaksha graphite inherited its isotopic signature (δ13CV-PDB of about –25‰) from hydrocarbons and is most likely derived from a metamorphic event.
Doklady Earth Sciences. 2025;523(2):226-233
226-233
Transformation of fuel oil in the Black Sea two and a half months after the tanker accident
Resumo
The paper presents the results of studies into the consequences of the ecological disaster in the Black Sea associated with the accident of the tankers Volgoneft-212 and Volgoneft-239 on December 15, 2024. The composition of chloroformed bitumen and hydrocarbons (aliphatic and polycyclic aromatic) on the beaches, in the suspension of bottom waters and bottom sediments is compared with the composition of fuel oil. It was found that the water area near Anapa is the most polluted. It is shown that the decrease in hydrocarbon concentrations 2.5 months after the accident is due to both their transformation on the shore and in the water, and the cleansing effect of bacteria. As a result, the amount of chloroformed bitumen decreased, and in its composition, low molecular weight alkanes and polyarenes.
Doklady Earth Sciences. 2025;523(2):234-240
234-240
PETROLOGY
Age of rare-metal pegmatites of the Aleksandrovskoye ore field, East Sayan pegmatite belt
Resumo
This paper presents the results of U–Pb (CA-ID-TIMS) geochronological studies of columbite-tantalite and zircon from the pegmatite vein of the Aleksandrovskoye ore field, which is part of the East Sayan rare-metal pegmatite belt. As a result of U–Pb geochronological studies of columbite, age estimates of 1825±3 Ma were obtained for the first time for the quartz core of the pegmatite vein and 1817±5 Ma for the zone of intense alteration of amphibolites in its exocontact. The age estimate of 1810±5 Ma was obtained for metamict zircon from the boundary zone of the quartz core. The studies indicate that the age of rare-metal pegmatites of the Aleksandrovskoye ore field of the East Sayan pegmatite belt differs significantly from the age of spatially conjugated granitoids of the Sayan complex (1.86–1.90 Ga).
Doklady Earth Sciences. 2025;523(2):241-251
241-251
Olivine from Namuaiv Pipe Aillikite, Kola Alkaline Province: The Primary Melt Evolution and Relation to Kimberlite Magmatism
Resumo
This study presents petrographic and mineral chemical data for olivine in aillikites from the Namuaiv pipe intruded into the Khibiny Massif, the Kola Alkaline Carbonatite Province. Two distinct olivine populations are identified: phenocrysts and xenocrysts. The phenocrysts crystallized from the aillikite melt, whereas the xenocrysts were entrained from the mantle substrate. Xenocrysts are characterized by high Mg# (0.89–0.91) and elevated concentrations of Ni and Ti, and are compositionally similar to kimberlitic olivines, but differ from them by significantly higher Ca contents. Elevated CaO concentrations in olivines from the aillikites of the Namuaiv pipe may reflect differences in the metasomatic processing of the mantle source (carbonate or aqueous fluid) or the intensity of its lherzolitization. The differences in the evolutionary trends of olivines from aillikites and kimberlites are caused by the assimilation of lithospheric material (mainly orthopyroxene) during the ascent of kimberlitic melts.
Doklady Earth Sciences. 2025;523(2):252-261
252-261
Composition and formation conditions of urtite magmas of the Chik intrusion of alkaline rocks (southeastern Tuva): data from the study of melt inclusions
Resumo
Based on the method of melt inclusion study, the magma composition and formation conditions of melts involved in the formation of urtites of the Chik intrusion of alkaline rocks (southeastern Tuva) are studied. The mechanisms of their formation are identified. Primary melt inclusions are studied in nepheline and garnet from the urtite. Amphibole, sphene, garnet, sodalite, banalsite, calcite, and zeolite are identified among the daughter minerals of the melt inclusions. It was found that nepheline crystallized in the temperature range of 1100 – 1120°C. It is shown that the glasses of homogenized mеlt inclusions in nepheline are characterized by wide variations in SiO2 contents, from 37 to 46 wt. %, Al2O3 – from 10 to 18 wt. %, CaO – from 5.6 to 19 wt. %, and increased concentrations of alkalis (11–15 wt. %), FeO (11–13 wt. %), TiO2 (up to 3.4 wt. %) and P2O5 (up to 2.5% wt. %). The chemical composition of the glasses of homogenized melt inclusions in garnet is similar to the most differentiated composition of the glasses of melt inclusions in nepheline. It contains 47 wt. % SiO2, 1 wt. % TiO2, 18 wt. % Al2O3, 9 wt. % FeO, 7 wt. % CaO and 16 wt. % of alkalis (Na2O + K2O).The results of the study of melt inclusions in urtite minerals, as well as the analysis of the composition of various rocks of the Chik massif (urtites, melteigites, and ijolites, including their calcite and garnet-containing varieties), suggest the involvement of gravitational and clystallization differentiation of magma in their formation. The data obtained refute the hypothesis of the metasomatic nature of the urtites of the Chik intrusion of alkaline rocks (southeastern Tuva) and provide compelling evidence for their magmatic genesis.
Doklady Earth Sciences. 2025;523(2):262-269
262-269
MINERALOGY
Structure and Raman spectroscopy of a new mineral, isostructural to lindquistite, from a xenolith of the Obnazhennaya kimberlite pipe (Kuoykskoye field, Yakutsk kimberlite province)
Resumo
The structure of a new mineral, isostructural to lindquistite, with the idealized crystal chemical formula (K, Ba)Fe3+(Mg,Fe)4(Al,Cr3+,Ti4+)13O27, has been studied by single-crystal X-ray dif-fraction analysis. This mineral was identified in a polyphase inclusion in alumochromite from a garnet-spinel lherzolite xenolith from the Obnazhennaya kimberlite pipe (Kuoykskoe field, Ya-kutsk kimberlite province). The parameters of the hexagonal unit-cell were obtained: a = 5.81093(15) Å, b = 5.81093(15) Å, c = 32.2003(10) Å, V = 941.63(4) Å3, space group P63/mmc, Z = 2. The mineral has layered structure of a mixed type. It can be described as a se-quence of 14 cubic and hexagonal dense-packed layers formed by oxygen atoms. In each 7th layer, large cations X (K+ and Ba2+) are placed in 1/4 oxygen positions, which occupy position 2b and are surrounded by 12 oxygen atoms. O2– and X ions of close radii form the densest pack-ing, while T (Mg2+, Fe2+), M (Al3+, Cr3+, Ti4+), and A (Fe3+) ions occupy voids. It was found that the new mineral is isostructural to lindquistite and hexaferrite of the W-type. The refinement of the mineral structure as a polytype of the magnetoplumbite structure does not reflect the rever-sal of the layers. The data obtained can be used to justify the identification of a separate lind-quistite group, since the studied new mineral is the second finding in this group.
Doklady Earth Sciences. 2025;523(2):270-279
270-279
Mineralogy
Resumo
The Early Cretaceous post-collisional adakites of the Stanovoy superterrane in the Russian Far East are geochemically similar to adakites associated with slab destruction and break-off in collisional and post-collisional tectonic settings. The Stanovoy adakites contain microminerals of Th, U, Ag и Au in association with amphibole, biotite, feldspars, zircon, apatite, monazite, rutile, F-bearing titanite, zirconolite, ilmenite and magnetite. Textural and compositional characteristics of these microinclusions suggest formation during crustal differentiation of adakite melts derived from hybridization of sulfide-rich mafic crust under large collisional structures by deep high-temperature F–P–Ti–Zr–Th–U–REE-rich fluids. It is concluded that adakites with such microminerals may serve as indicators of post-collisional processes responsible for the formation of rare and strategic metal deposits within ancient collisional margins of the Precambrian cratons.
Doklady Earth Sciences. 2025;523(2):280-286
280-286
GEODYNAMICS
Peculiarities of the mid-lithospheric discontinuity in the East-European craton collision zone
Resumo
The receiver function method was used to construct kinematic models of the collision zone of the central part of the East European craton based on data from five broadband seismic stations. A layer of lower velocities with upper boundary at a depth of about 90 km was identified in the upper mantle of the Sarmatia protocraton, marking a mid-lithospheric discontinuity (MLD). The thickness of the identified layer is about 50 km. According to data from stations located in the collision zone, MLD is not detected.
Doklady Earth Sciences. 2025;523(2):287-291
287-291
PALEONTOLOGY
Traces of pelagic biota in siliceous rocks of the Upper Cambrian of Southern Kazakhstan
Resumo
The lower part of the Burubaytal Formation that encompass the Upper Cambrian and Lower Ordovician cherts in the in the Southwestern Balkhash region of Southern Kazakhstan is enriched by organic detritus. This detritus consists of numerous fecal pellets composed of para- and protoconodont elements, as well as spherical acritarchs, individual acritarchs, and conodont elements. Additionally, there are scattered carbonaceous, finely dispersed organic matter and clumps of this matter. These findings indicate a significant contribution of pelagic organisms in the formation of a vertical flow of organic matter from the pelagic zone to the deep-sea bottom and an episode of increased burial of organic matter at the beginning of the Batyrbaian Stage in the Late Cambrian corresponding to the TOCE (Top of Cambrian Excursion) isotopic event.
Doklady Earth Sciences. 2025;523(2):292-297
292-297
GEOPHYSICS
Displaying the structure and rheological properties of a fault zone in the characteristics of background seismicity
Resumo
Spatial heterogeneity of structural and rheological properties of a fault is one of the key factors determining the dynamics of its deformation. The paper analyzes spatial and temporal patterns of seismic localization in several segments of the San Andreas fault zone. Groups of background and clastered events are distinguished. It is shown that background events exhibit structural features of the fault. Asperities in the fault plane appear as dense clusters of background events. Foci of strong earthquakes with magnitudes exceeding the maximum magnitude of background events 1.5–2 times completely rupture at least one contact spots. The fault area located between the asperities controls the slow postseismic slip and, consequently, postseismic aftershock activity. The number of aftershocks is maximal at the boundary of the earthquake’s focal area and decreases monotonously with distance from the hypocenter. In the area between the asperities, the speed of aftershock migration is 0.01–10 km/day.
Doklady Earth Sciences. 2025;523(2):298-304
298-304
Three-Dimensional Model of Convection in a Really Heterogeneous Mantle as a Basis for Quantitative Generalization of Plate Tectonics for the Present Stage of Earth Development
Resumo
Using the Stokes equation and non-Newtonian rheology, instantaneous velocities of three-dimensional flows in the Earthʼs mantle are calculated based on the global seismic tomography model SMEAN 2. The model automatically takes into account the main forces acting in the mantle and on the Earthʼs surface. The constructed 3D model of mantle flows describes well the horizontal movements of the Earthʼs surface, which are observed using space geodesy and provides a quantitative basis for interpreting the features of regional geological processes. The constructed spherical 3D model of modern global geodynamics is a quantitative generalization of the theory of plate tectonics for the current stage of the Earthʼs development.
Doklady Earth Sciences. 2025;523(2):305-310
305-310
SEISMOLOGY
Forecast of seismic and geodynamic conditions before and after the earthquake of March 28, 2025, M7.7, in Myanmar
Resumo
The paper presents a comprehensive analysis of the seismic and geodynamic conditions before and after the March 28, 2025, M7.7 earthquake in Myanmar. The results of a global test of the M8 algorithm for predicting earthquakes with a magnitude of 7.5 and greater for this region are considered. It is analyzed how expected the earthquake was in terms of long-term seismic hazard based on seismicity data alone. A geodynamic analysis is performed to assess the seismogenic potential of the Sagaing fault before and after the earthquake. The risk of aftershocks is assessed. A model of the earthquake source is constructed to test the supershare property of the rupture and interpret the anomalously large length in the US Geological Survey model.
Doklady Earth Sciences. 2025;523(2):311-321
311-321
The March 28, 2025 earthquake in Myanmar: A rupture surface model from satellite data on earth surface displacements
Resumo
The paper presents a model of the rupture surface of the Mw 7.7 earthquake that occurred in Myanmar on March 28, 2025. The model is based on the solution of the problem of stresses and strain state of a spherical radially stratified planet due to displacement on a rectangular section located within it (F. Pollitz, USGS) and displacement data obtained during the earthquake and within six following days, derived from Sentinel-1A satellite imagery (March 22, 2025, and April 3, 2025) using the offset tracking method. A regularization condition was applied, favoring slip directions close to pure right-lateral strike-slip. The results show that the main displacements on the fault occurred within the upper 5 km of the Earthʼs crust and ranged from 5.0 to 6.7 meters, while at greater depths the displacements were significantly smaller. An exception was a small segment of the fault located between 21.28° and 21.56°N, where the displacement at the upper level was estimated at 4.5 meters. Possible causes for the slight displacement deficit are explained in the study by the peculiarities of the aftershock process development. The constructed rupture surface model does not show significant variations in slip magnitude along the fault or the presence of local thrust or normal faulting components. GPS data collected since the early 2000s also indicate uniform elastic strain accumulation along the fault at an average rate of 20 mm/year, suggesting that the fault was locked over its entire length. The obtained results refine the rapid-response model presented on the US Geological Survey website by accounting for the Earthʼs sphericity and radial layering, as well as by applying the regularization condition for slip direction alignment with right-lateral strike-slip motion.
Doklady Earth Sciences. 2025;523(2):322-330
322-330
OCEANOLOGY
Transformation of Bottom Pressure Generated by Sea Wind Waves into Micro-Displacements of the Upper Layer of the Earth's Crust
Resumo
A quantitative assessment of the relationship between variations in bottom pressure created by wind waves and micro-displacements of the upper crust layer is given based on data from a laser hydrosphere pressure variation meter and two laser strainmeters. Based on experimental data, the dependence of the coefficient of transformation of bottom pressure into elastic oscillations of the upper crust layer on periods of wind waves is derived.
Doklady Earth Sciences. 2025;523(2):331-336
331-336
ATMOSPHERIC AND HYDROSPHERIC PHYSICS
Diagnostics of the regional carbon balance based on satellite observations of carbon dioxide
Resumo
A new approach to diagnostics of the regional carbon balance is presented, which involves optimization of parameters of an ecosystem carbon exchange model using satellite observations of the column-average dry-air mole fraction of CO2 in the atmosphere (XCO2) and a mesoscale chemistry-transport model. The potential of the suggested approach is demonstrated through its application to estimate ecosystem CO2 fluxes in Central Siberia using XCO2 data from the OCO-2 satellite.
Doklady Earth Sciences. 2025;523(2):337-343
337-343
GEOECOLOGY
Britholite-based matrix for actinides isolation
Resumo
Britholite, a Ca-REE silicate sample with an apatite structure, was produced by cold crucible induction melting. Britholite has a simple composition, high capacity for actinides, and is stable in heated aqueous solutions. For the first time, the leaching rates of Nd (imitator of minor actinides) with water and brine at 200–250°C were determined to be 10–3 – 10–5 g/(m2 × day), which corresponds to a congruent dissolution of the matrix at a rate of 1 micron per 3–300 years.
Doklady Earth Sciences. 2025;523(2):344-352
344-352