Vol 518, No 1 (2024)

For the northeastern part of the Chingiz-Tarbagatai segment of the Boshchekul-Chingiz folded area, U-Pb age estimates of Middle Paleozoic granitoid complexes were obtained for the first time, and their geochemical features were described. New data indicate a wide distribution of Late Silurian granitoids, represented by I-type rocks, in this territory. Early Devonian rocks form a number of separate volcano-plutonic structures, the granitoids of which can be classified as A-type. The compositional features of granitoids formed during the Cambrian-Devonian allow us to trace the evolution of the crust of this part of the Chingiz-Tarbagatai segment from an ensimatic island arc to a volcanic belt with relatively mature continental-type crust.

The paper presents the first isotopic U-Pb study data (LA-ICP-MS method) of zircon from intrusive rocks of the Molo-Sarychat pluton situated along the deep-seated fault system of the “Nikolaev Line” in the eastern Kyrgyzstan. The intrusive rocks from this pluton belong to the high-potassic calc-alkaline to shoshonitic series. Intense Mo(-W-Cu-Au) (mainly molybdenum-porphyry) mineralization is spatially and genetically associated with this pluton. Together with the other Au, W and Cu deposits and occurrences, this mineralization is part of the extended metallogenic belt of Tien Shan; however, occurrences of molybdenum-porphyry mineralization are still rare in this belt. The concordant isotopic U-Pb ages of zircon autocrysts indicate the crystallization of quartz monzonite (293.3±4.2 Ma) and monzogranite (286.6±2.4 Ma) in the Early Permian. Zircon antecrysts dated at 306-320 Ma are also present. The crystallization age obtained corresponds to a post-collisional epoch of the development of this territory but the presence of the antecrysts expands the pluton emplacement to the Late Carboniferous-Early Permian, which, as a result, spanned over initially subduction-related and then post-collisional tectonic settings. Correspondingly, a post-collisional setting of the Mo(-W-Cu-Au) (molybdenum-porphyry) mineralization is established; it is related to the pluton studied and was formed after the emplacement of quartz monzonite (early stage) and monzogranite (late stage). Significant enrichment in Mo can be related to its progressing accumulation during magmatic differentiation causing the emplacement of quartz monzonite and especially monzogranite. These processes occurred under the more mature post-collisional tectonic regime, with possible formation of intermediate magma chambers in the Paleoproterozoic metamorphic rocks and ancient granitoids. The age dates determined for rocks from the Molo-Sarychat pluton are similar to those identified for the igneous and metasomatic rocks of the large Kumtor gold deposit that is also associated with the “Nikolaev Line”.

The content and distribution of precious metals in fine-grained bottom sediments of the southwestern part of the Chukchi Sea have been studied. The ubiquitous or local enrichment of silver, gold, platinum and palladium according the earth's crust average, as well as the enrichment of sediments accumulated during the technogenic period (last decades) relative to pre-technogenic (Late Holocene) deposits with gold, platinum and palladium are shown. Using the methods of multicomponent statistical analysis of the total chemical composition of sediments, the differences in the conditions for the accumulation of precious metals in modern and late Holocene deposits are shown, possible sources of input are determined and the possibility of technogenic enrichment is substantiated.

On the White sea islands and coast of North Karelia, in the Loukhi region, carbonate-silicate and quartz veins are widespread, confined to bodies of Early Proterozoic metabasites and their contacts with host gneisses. The isotopic characteristics of coarsely crystalline vein carbonates (δ¹⁸O and δ¹³C), as well as associated quartz (δ¹⁸O) and biotite (δ¹⁸O and δD), were studied. The isotopic composition of oxygen suggests biotite-quartz-carbonate equilibria during the formation of veins at temperatures of 520–450°C. The O and H isotopic characteristics of biotite correspond to the equilibrium of the fluid with metamorphic rocks. At the same time, the isotopic compositions of O and C carbonates indicate different sources of CO₂ in fluids. There are three groups of carbonates according to δ¹⁸О and δ¹³С. The first group has “magmatic” isotopic characteristics of the CO₂ source (δ¹⁸О_VSMOW = 7.1… 12.1‰; δ¹³С_VPDB= = –6.3…–4.5‰). Carbonates of the second group have high δ18О and δ13С, characteristic of Precambrian sedimentary carbonates (δ¹⁸О_VSMOW = 21.9…24.7‰; δ¹³С_VPDB = –2.2…-2‰), similar to those described earlier in the neighboring Engozero sector of the Belomorian mobile belt. In the third group, the δ¹³С values are similar to the carbonates of the first group, and δ¹⁸О – to the second group (δ¹³С_VPDB= = –1.7…0.9‰, δ¹⁸О_VSMOW = 6…12‰). The O and C isotopic compositions of carbonates of the third group can be obtained from the action of a putative magmatic fluid on both the primary sedimentary source of metamorphic fluids and redeposited vein carbonates.

This paper describes secondary crystallized melt inclusions entrapped in magnesiochromite of lherzolite xenolith from the V. Grib kimberlite pipe (Arkhangelsk diamondiferous province). The inclusions represent snapshots of the melt, associated with magmatic processes that subsequently formed the V. Grib kimberlite pipe. Various Na-K-Ca-, Na-Mg-, Ca-Mg-, Mg-, Ca-carbonates, Na–Mg-carbonates with additional anions PO₄^3-–, Cl^–, SO₄^2–, chlorides, sulphate, phosphate and silicate were identified among the daughter phases. The mineral assemblage of daughter phases, carbonate (77 vol. %) and silicate (15 vol. %) content and Ca : Na : K ratios within the inclusions show that inclusions’ parental melt was an alkali-rich carbonate liquid with low amounts of SiO₂ (≤6 wt%) and H₂O (≤0.6 wt%). Serpentine is known to be the main water-rich mineral in kimberlites, however the water sources during serpentinization of kimberlites and the H₂O content in kimberlite melts remains controversial issue. The absence of serpentine and low water content in the studied melt inclusions in comparison with those in the kimberlites of the V. Grib pipe (10–14 wt. %) indicate predominance of external fluids in the serpentinization of these kimberlites.

The study of the Khanmeykhoy Formation of the central zone of the Kharbey amphibolite-gneiss complex showed that the amphibolites, shales and plagiogneisses common here form two primary igneous series: low-alumina tholeiitic metabasalts of normal alkalinity and a differentiated series of high-alumina rocks from metatrachybasalts to metarhyolites with high alkalinity. According to the zoning of garnets, progressive and regressive branches of metamorphism are recorded, the peak conditions of which, according to calculations using the winTWQ program, correspond to the high-temperature stage of the amphibolite facies at high pressures (T – 690–750°C, P – 8.1–9.4 kbar). For the first time, metamorphic zircon from Grt-Bi plagiogneiss with low Th/U ratios of 0.01–0.04 and weakly expressed positive cerium (Ce/Ce* = 1.4–1.7) and negative europium (Eu/Eu* = 0.7–0.9) has been identified in the anomalies, the age of which, according to the results of the U-Pb LA-ICP-MS isotope method, is estimated to be Early Carboniferous (359–341 Ma). This time apparently characterizes the transition from the peak of metamorphism to the regressive stage associated with the exhumation of rocks. The results obtained indicate the formation of the Kharbey amphibolite-gneiss complex during the formation of the Ural orogen and allow us to consider it as an indicator of Paleozoic collision processes.

A mineral with composition Pd(Bi_0.54Sb_0.46) – intermediate between sobolevskite, ideally PdBi, and sudburyite, PdSb, from the Chineisky Deposit (Transbaikal region, Russia) was studied by SEM and XRD methods. Its crystal structure solved and refined (R = 3.02%) based on the single crystal X-ray diffraction data. The structure is orthorhombic, and the space group is Cmcm. The unit-cell parameters are a = 4.1465(4), b = 7.1782(6), c = 5.6843(4) Å, V = 169.19(2) ų, Z = 2. The series of the structures β-PdBi – Pd(Bi_0.6Sb_0.4) – PdSb and sobolevskite – sudburyite are discussed.

Madagascar basin bottom morphology from Mauritius Isl. to South-West Indian Ridge (SWIR) is represented by a ridge-echeloned topography type of the spreading basement, the azimuth of which differs by ~90° for the basin north of the SWIR and its wedge-shaped sublatitudinal rift system, separated by an abyssal escarpment. A genetic definition of this bottom topography shape is given, which is formed when the existing basement breaks up and the crust accretion begins orthogonal to the azimuth that existed before the rupture. The formation of the wedge in the eastern part of the SWIR began ~41 Ma ago and is expressed by higher (±1100 m) amplitudes of relief variations than at the basement before the rupture (±250 m). The change in morphology is also associated with a ~24° change in the azimuth of lithospheric block spreading north of the SWIR, which opened up a new space for accretion. The morphology of the relief in the wedge and beyond shows the relationship of its parameters with a slowdown in the spreading rate by almost 3 times when the kinematics of the plates changed. The high-amplitude ridge relief in the ultra-slow segment of the SWIR with signs of nontransform displacement is combined with the maxima and minima of the Bouguer anomalies, in the localization of which, according to literary data, serpentinized peridotites and basalts are obtained, indicating the presence of detachments with the exposure of ultramafic rocks and minimal magmatic output. The Bouguer anomalies along the regional profile fully reflect the deep density inhomogeneities, which for intraplate volcanic structures have a much greater effect of upper mantle density loss than for the active interplate boundary of the SWIR. The absence of a deep upwelling under the newly formed SWIR segment and the presence of a “cold” gap in the “hot” lenses of mantle according to seismotomography data indicates the impact of tangential forces in the lithosphere that are not associated with general mantle convection. The formation of a new orthogonal rift system with ultra-slow rates is an adaptation to variations in the kinematics parameters of adjacent lithospheric plates.

This study describes a newly found frozen carcass of an extinct woolly rhinoceros of young age (4–4.5 years old) living during the Karginian Interstadial of the Late Pleistocene (32 440±140 years ago). The size traits of this specimen are compared to those of 1–1.5 year-old juveniles as well as adults of C. antiquitatis found previously. Studies of a newly found carcass allowed to fill the gaps in information about ontogenesis of the woolly rhinoceros, to illustrate the process of color change of its wool, as well as to reveal a new anatomical feature of C. antiquitatis – the presence of a fat hump. Numerous remains of microscopic crustaceans were found in the wool, including members of the genus Moina (Cladocera: Moinidae), currently absent in the region. The former were relatively common in Pleistocene temporary water bodies of this region. The burial of the rhinoceros body occurred in a shallow (apparently temporary), fishless water body.

Heterogeneous data obtained with different accuracy are considered in the framework of combinatory theory and variational principle. Discrete character of acquired data about physical fields and their sources imposes a series of limitations to the possibility of an adequate interpretation of the geophysical information. Combinatoric methods of discrete mathematics allow us to accurately formulate the main criteria of the data selection for the following approximation of the anomaly filed elements as well as for controlling the accuracy of solutions to linear and non-linear inverse problems.

The thermohaline regime trends of the Black Sea basin in 2000–2021 were studied based on the data from three retrospective analysis (reanalysis) of the Black Sea hydrophysical fields. It is shown that the cumulative effect of an increase in average the sea surface temperature (SST) and the softening of winter conditions in the Black Sea area in recent 7–8 years leads to the record warming and then the disappearance of the ventilated Black Sea cold intermediate layer (CIL) in its traditional sense by 2020 year. In addition, accelerated warming of sea waters has been observed within the permanent (main) pycnocline in the last 7–8 years. Changes in the thermal regime of the upper sea layer are accompanied by a continued increase in salinity in the main pycnocline.

The results of the analysis of images of surface heat flows in the areas of origin of a number of hurricanes in the Gulf of Mexico and the tropical Atlantic, obtained with the satellite microwave and IR radiometric measurements, are presented. An increase in the intensity of latent and sensible heat fluxes during 4–5 days in the periods preceding the origin of hurricanes and their localization in certain areas, is discovered.

Factors influencing the geochemical migration of elements during the development of artificial plant communities on degraded peat soil with high levels of copper and nickel contamination using serpentine-containing materials are considered. Monitoring of reclamation sites during a four-year field experiment showed that the grass cover is capable of sustainable functioning by neutralizing the acidity of industrially polluted peat soil, reducing the toxicity of soil solutions, and eliminating the imbalance of macronutrients. Serpentine minerals act as a alkaline barrier, reducing the intensity of migration of copper and nickel compounds.

The paper addresses the issues of geodynamic research in Northern Eurasia over the past three decades with emphasis on the use of space technologies in geodesy and geodynamics. The main focus is on the GNSS system as the most widespread and effective tool for geodynamic research due to the compactness and relative ease of installation of ground-based tracking equipment, as well as the possibility of its autonomous operation. The importance of precise GNSS positioning for monitoring small-scale geodynamic displacements of the earth’s surface, which requires millimeter-scale measurement accuracy, is emphasized. The issues of development of a precise reference frame for geodynamics and maintaining its long-term consistency based on the International Terrestrial Reference Frame (ITRF) are considered, as well as the problems and prospects of precise satellite geodetic measurements and geodynamic research in the context of the current reduction in interaction with international geodetic data centers. To solve the problems that have arisen, ways are proposed based on the arranging a subcontinental-scale system for equalization of raw GNSS measurements. The capabilities of the used GNSS network for solving problems of geodesy and geodynamics are demonstrated by the example of the analysis of the tectonic rigidity of cratons of Northern Eurasia and the impact of motion of adjacent tectonic plates and variations of these motion in the past geological eras on the contemporary geodynamic setting of these cratons.