Pseudo-secondary inclusions in superdeep natural diamonds, whose formation is associated with metal–carbon melts, represent new sources of information on the mineralogy and geochemistry of the mantle. However, many aspects of their genesis remain contentious. This work presents, for the first time, the results of experimental modeling of the formation conditions of pseudo-secondary inclusions in diamonds obtained under a decreasing temperature regime in the iron–carbon system at mantle P–T parameters. A detailed study of the crystals and inclusions revealed the main factors responsible for the formation of such inclusions. It is established that the dominant stress generators in the crystals are numerous dispersed iron-bearing inclusions ranging in size from 60 to 600 nm. The heterogeneous distribution of dispersed inclusions, controlled by the surface topography of the growing crystal, creates a mosaic structure of the diamond matrix, which favors the formation of stress concentrators. Relaxation of these stresses under decreasing temperature conditions leads to brittle deformation and the formation of cracks along weakened zones. It is found that crack healing due to regeneration and overgrowth by overhanging growth layers ultimately forms pseudo-secondary inclusions. The experimentally substantiated mechanism of pseudo-secondary inclusion formation may represent one of the possible scenarios for the formation of morphologically similar inclusions in natural diamonds and other minerals.
The relevance of this study lies in the systematic investigation of the causes of geophagy. Geological and hydrobiogeochemical studies were conducted in two areas on the western coast of Lake Baikal (spurs of the Primorsky Ridge), where wild ungulates consume carbonate rocks. It was established that these rocks contain various mineral forms of rare earth elements that are readily extracted under slightly acidic conditions (HCl, pH 2). Local landscapes are notable for an unusual plant-food Ca : Mg : P ratio of 3 : 1 : 1 (compared with the norm of 0.6 : 1 : 1) and extremely low contents of rare earth elements (average sum of Y and Sc = 0.25 ± 0.11 mg/kg). The average Na content, extracted from carbonate kudurites under slightly acidic conditions across eight samples, is 244 mg/kg, slightly exceeding that in dry vegetation. The average value of extractable rare earth elements (13.46 mg/kg) is more than 50 times higher. Field and laboratory studies, including a review of the literature on the role of rare earth elements in mammals, suggest that ungulates’ consumption of carbonate rocks is driven by their need for specific rare earth elements essential for the normal function of the neuroimmune-endocrine system.
This paper presents the new isotopic U–Pb data (LA-ICP-MS) for zircon from intrusive rocks of the large Vostok-2 tungsten–base-metal(–gold) deposit. This deposit, together with other tungsten, tin, and gold deposits, is part of the metallogenic belt which extends along the Central Sikhote-Alin Fault and corresponds to the occurrence of Early–Late Cretaceous magmatism and mineralization formed due to the development of a transform continental margin. The deposit comprises large bodies of pyroxene skarn altered during the development of the postskarn metasomatic rocks and related to intensive scheelite–gold–sulfide (with abundant pyrrhotite) mineralization and represents a “reduced” type of tungsten skarn deposits. The concordant isotope U–Pb dates were obtained for zircons from different granitoid rocks of the mineralized area: 109.7 ± 0.7 and 110.4 ± 0.6 Ma (MSWD = 0.047 and 0.003) (granodiorite and “plagiogranite” of the Central stock), 106.9 ± 1.6, 106.9 ± 0.7, 108.2 ± 0.8, and 108.0 ± 0.8 Ma (MSWD = 0.13, 0.0004, 0.27, and 0.54) (granodiorites of the Dalnensky massif), and 107.6 ± 1.7 Ma (MSWD = 0.45) (granite–porphyry). These data are indicative of a a generally low but persistent age decrease of rocks from the Dalnensky massif, as compared to those from the Central stock. These study results are consistent with distinguishing the latter as a distinct igneous complex earlier suggested based on their petro-geochemical signatures. Such complex of “small intrusions” could be the most productive for Au–W to W–Au mineralization in the region. The dates obtained for intrusive rocks from the Vostok-2 deposit are similar to those of the intrusive massifs accompanied by other tungsten–base-metal deposits in the belt as well as by some pluton-related (“reduced intrusion-related”) gold deposits. The rocks studied also contain “ancient” zircon xenocrysts inherited from various crustal protoliths and dated by a broad range of isotopic U–Pb ages.
A two-stage model of tectonic earthquake initiation has been developed as a result of laboratory and numerical experiments. During the shear deformation of a tectonic fault, shear stresses concentrate and a slip deficit accumulates at tectonic asperities. At the first stage when stresses reach the fault strength, a slow slip is initiated and propagates from the boundary of the asperity across its entire area. At the second stage, the slow slip covering the entire area of the asperity, transforms into a dynamic slip. The dynamic slip is accompanied by radiation of a high-amplitude seismic pulse, and the size of the seismic source corresponds to the size of the asperity.
U–Pb dating of gabbronorites from the upper part of the layered series of the Argydzhek pyroxenite–anorthosite–gabbronoite massif in the Arzybey terrane, which belongs to the Kulibin сomplex, has revealed that its formation time corresponds to the Vendian (ca. 630 Ma). This fact allows correlating age of the intrusions of the Kulibin complex with the high-Ti Lysan ultramafic-mafic complex in the junction zone of the Derba terrane and the Sisim-Kazyr island-arc system of the Central Asian Orogenic Belt, as well as with the alkaline intrusions of the Zima complex in the Siberian craton, which is of plume origin. The subduction geochemical characteristics of gabbroids from the Argydzhek intrusion are explained by melting of the suprasubduction lithospheric mantle of the Arzybey terrane under the influence of a mantle plume, which is indicated by the massifs of the Lysan complex. Our data significantly expand the range of Vendian plume-induced mantle magmatism in the folded frame of the Siberian craton.
Mineral exploration in coastal regions is challenging due to rugged topography. Hyperion imagery, known for its cost effective and spectral precision, is used for mineral identification based on physical, chemical, and optical properties. This study focuses on the identification and mapping of carbonate and silicate minerals using Spectral Angle Mapper (SAM) and Mixture Tuned Matched Filtering (MTMF) algorithms. SAM classifies each pixel into a single dominant mineral type based on spectral similarity, whereas MTMF accounts for spectral mixing, enabling sub-pixel detection of target minerals. The software “Environment for Visualizing Images” (ENVI) has been used to compare the obtained spectra (OS) with reflectance spectra (RS) from the USGS (United States of Geological Survey) database for result validation. Overall, SAM demonstrated higher classification accuracy (overall accuracy (ОА): 84.16
The study of metal element species distributions and the environmental factors influencing their transformation was critical for water quality monitoring and pollution control. This study employed Visual MINTEQ software to analyze the species distributions of metal elements in water and their variation patterns under the influence of environmental factors. This study focused primarily on the transformation of the chemical speciation of metals, including Pb, Ni, Mn, Zn, Al, Ca, Mg, Na, and K, under various pH and temperature conditions. The results showed that pH significantly affected the species distribution of metal elements. Specifically, under acidic conditions, aluminum existed mainly as a hydrate, whereas under neutral to alkaline conditions, it transformed into aluminum salts. Most elements existed in a nonionic form under alkaline conditions. Temperature changes significantly altered the solubility and speciation of Al, with only a minor impact on other elements. The concentrations of metal elements were analyzed under different water quality standards, revealing notable differences in species transformation patterns across various aquatic environments. The toxicity of different metal elements and their effects on water quality also varied under different environmental conditions. Overall, this study not only enhanced the theoretical framework of metal speciation analysis but also provided a scientific foundation for water quality management and pollution control.
The deep Paleogene of the Third Member of Liushagang Formation (E2l3) in the Weixinan Sag represents a promising yet challenging exploration frontier, as conventional shallow to mid-depth reserves approach maturity. Recent drilling campaigns in the WZ11-6 structure have confirmed significant hydrocarbon indications; however, extreme reservoir heterogeneity and complex formation mechanisms hinder efficient development. This study adopts an integrated approach, combining drilling, seismic interpretation, petrography, and petrophysical data, to characterize the E2l3 reservoir, map sedimentary microfacies, and identify the principal controls on high-quality reservoir formation. Key findings include: (1) the reservoir is predominantly composed of quartz-rich sandstones, with moderate sorting and low structural maturity; (2) ten lithofacies are identified, reflecting a distal fan-delta front environment, subdivided into five microfacies: subaqueous distributary channels, mouth bars, sheet-like sand body, distal mouth bar, and interdistributary bays; (3) reservoir quality is primarily influenced by sedimentation—controlling initial grain size and depositional fabric—diagenesis (including compaction and cementation that reduce porosity, and dissolution that enhances porosity), and tectonic fracturing, which creates fluid migration pathways; (4) through the integration of porosity inversion, microfacies mapping, and provenance analysis, the spatial distribution of high-quality reservoirs is predicted, with sweet spots primarily located in subaqueous distributary channels and mouth bars. This study provides a robust framework for predicting deep E2l3 reservoir characteristics, offering valuable insights for future exploration in the Weixinan Sag and similar sedimentary basins.
Seismoacoustic profiles along the western passive margin of the Chain transform fault made it possible to define anomalies in the wavefield within the upper sedimentary layers: abrupt loss of coherency, box folds, “flat” and “bright” acoustic spots, and thrust-type faults. These features are interpreted as signatures of the ascending fluid flow. The anomalies are localized in the transition zone between the Romanche and Chain transform faults, where negative Bouguer gravity anomalies are indicative of a reduced density in the upper mantle to a depth of several tens of kilometers. It is important to note that the sedimentary cover is less than 1000 m thick in these areas. Hence, the mud volcanism can be ruled out as a process for deep fluid ascent. Based on the total array of field data and theoretical prerequisites, the origin of the fluids is attributed to serpentinization. This process depends on the presence and activation of deep-seated fault systems within the intraplate setting. This fact explains the spatial correlation of the anomalies with the transform trough.
The three-dimensional global temperature and flow velocity distribution in the current Earth’s mantle is analyzed and calculated using the global seismic tomography data, the SMEAN 2 model. In several mantle regions, the areas with a hot or cold material have a subhorizontal rather than a subvertical orientation. This may be due to the presence of additional mantle boundaries, similar to the boundary between the upper and lower mantle, at a depth of about 900, 1200, 1600, and 2200 km.
Early productive pyrite-arsenopyrite mineralization with invisible gold and late pyrite mineralization with free gold, separated by the intrusion of Middle Permian diorite porphyrite dikes, are identified in the Middle-Late Permian volcanogenic-sedimentary rocks of the Vladivostok Formation (southern Primorye). Arsenopyrite, the dominant ore mineral determining the commercial significance of the ores, is characterized by high gold content (up to 150 g/t, and possibly higher), compositional non-stoichiometry (S/As varies from 1.04 to 1.18) and Fe enrichment. Submicroscopic inclusions of gold are discovered in monomineral arsenopyrite samples decomposed by a specially developed method using a mixture of ammonium bifluoride and ammonium sulfate. This may be a consequence of their transport and cocrystallization during ore genesis. The isotopic composition of the deposit’s sulfides corresponds to a magmatic source of the ore-forming material. The age of the intra-ore diorite porphyrite dike, determined from zircon by the U–Pb method (LA-ICP-MS), is 275 ± 1.5 Ma.
Tourmaline is a common borosilicate, an important indicator of mineral formation conditions, and a promising material for various technological applications. Crystals of a Zn-bearing tourmaline analogue with a zinc content of up to 4.22 wt _□ 0.95 Na0.03Ca0.02)Y(Al2.88Zn0.12)Z Al_6.00^T (Si6O18)(BO3) _3^V (OH2.05O0.95)WO crystallizes in R3m space group with the unit cell parameters: a = 15.7596(2) Å, c = 7.0623(1) Å. Using Raman spectroscopy, it is shown that the intensity ratio of the bands associated with the (YO6) octahedra at 230 and 270 cm–1 depends on the zinc content in the structure of the Zn-bearing tourmaline analogue.
The “hump-shaped” REE distribution, established in pitchblende of the large-scale uranium mineralization at the Oktyabrskoye deposit (Streltsovka Ore Field, SOF), is expressed by a maximum in middle REE concentrations and, consequently, a significant increase (up to values of 2.2) in the Sm/Nd ratio compared to that in the volcanic rocks of the SOF ( 0.18). At an Sm/Nd ratio of 2, a reliably measurable radiogenic shift ∆(143Nd/144Nd)R is about 0.0004 per 100 Ma, which makes it possible to classify pitchblende (along with fluorite) as a promising Sm–Nd geochronometer for hydrothermal uranium ore processes. Based on the analysis of 10 microsamples of pitchblende extracted from three samples of pitchblende-carbonate veins, a Sm–Nd isochron was obtained with the following parameters: T = 137.4 ± 2.3 Ma, (143Nd/144Nd)0 = 0.512327 ± 0.000015, MSWD = 1.5. The resulting age uncertainty of ±2.3 Ma, determined by the scatter of data points around the isochron, is caused by the measurement uncertainties of 147Sm/144Nd and 143Nd/144Nd, as revealed by the analysis of the potential causes. The role of geochemical factors, primarily the heterogeneity of the initial Nd isotopic composition, is ruled out due to the limited range of ore samples used and the local sampling of the analyzed pitchblende. The coincidence of the pitchblende Sm–Nd date with the previously obtained U–Pb (ID-TIMS) data for the pitchblende (135.5 ± 1.0 Ma), as well as the Sm–Nd data for the post-ore fluorite (134.8 ± 1.3 and 135.8 ± 1.6 Ma) characterizes the Sm–Nd system of the pitchblende as closed, having not undergone “rejuvenation” due to the possible migration of Sm and Nd isotopes.
New data have been obtained on the taxonomic composition of microalgal assemblages (dinocysts and diatoms) from surface sediments collected in the Norwegian-Greenland Basin (NGB) in 2016‒2021 as part of the Shirshov Institute of Oceanology expedition program “European Arctic: Geological Record of Environmental and Climatic Changes.” The comparison with thanatocoenoses from the database samples collected prior to 2008 showed that microfossil assemblages from sediments retrieved in 2016‒2021 primarily from the zone influenced by the Arctic and Polar fronts include species that were previously characteristic of stations located further south and southeast. The differences in the taxonomic composition of dinocyst assemblages from the open parts of the NGB are primarily due to a slight increase in the proportion of the species Operculodinium centrocarpum against the background of a certain decrease in the abundance of Nematosphaeropsis labyrinthus cysts. A total of 80 species of diatoms have been identified within the diatom assemblages, dominated by thermophilic planktonic forms such as Asteromphalus robustus, Actinoptychus senarius, Coscinodiscus asteromphalus, and C. radiatus. Their distribution boundary has shifted northward compared to data from the turn of the 21st century.
Three-dimensional temperature fields constructed by using regression method based on satellite observations of ocean surface topography and temperature mainly in mid- and low-latitude regions of the Global Ocean for 2005–2022 are analyzed. Typical profiles of regression coefficients are presented for several regions of the Global Ocean. It is shown that seawater temperature fluctuations in phase with sea level caused by synoptic eddies with horizontal scales from 50 to 150 km predominate throughout the main thermocline. In the near-surface ocean layer, seawater temperature variations are largely coherent with changes in sea surface temperature (SST) and appear to be driven by submesoscale processes. Comparison of regression coefficient profiles within the anticyclonic gyre in the North Atlantic with the results of processing data from the POLYMODE hydrological surveys suggests that the patterns described above have remained stable for over forty years. A joint analysis of vertical temperature profiles derived from regression and those ones observed by ARGO floats shows that in areas of high eddy activity, the sea surface temperature variations in phase with sea level account for up to 70–80
Based on an analysis of Sentinel-1 radar images 2015–2024 covering the coastal waters off the Kamchatka Peninsula and the northern Kuril Islands, a database was compiled. The database contains 3895 manifestations of short-period internal waves and 1156 of submesoscale eddies. The analysis shows that these phenomena are a permanent and inherent components of the dynamics of regional coastal waters. The highest activity of both feature types was recorded during the summer season. Persistent areas of frequent occurrence (“hot spots”) were identified: Avacha and Kronotsky gulfs, the southeastern shelf of the Kamchatka Peninsula, and the area east of the Fourth Kuril Strait. A comparison with ichthyoplankton survey data (approximately 1500 stations for 2003–2024) reveals direct spatial overlap: areas of increased occurrence of submesoscale processes are largely confined to the main aggregation zones of walleye pollock eggs and larvae (Gadus chalcogrammus). This observed spatial correspondence suggests that submesoscale processes should be regarded as a previously unaccounted abiotic factor, warranting their inclusion in the assessment of ecological conditions for the reproduction of commercial resources in the region.
New paleoceanographic data were obtained from a comprehensive study of Holocene sediments in the western part of the Barents Sea (the Kveithola Drift). Diatom assemblages, geochemical proxies (Ti/Ca, Zr/Ca, Ca/Fe, and Al/Zr ratios), and magnetic susceptibility reveal the paleoceanographic evolution covering between approximately 3.3 and 9.3 cal kyr BP. An increase in sea surface temperature up to 3.9°C accompanied by a reduction of sea ice cover during the late Early to early Middle Holocene was observed. In the second half of the Middle Holocene minimum sea surface temperatures (0.8–1.8°C) associated with the onset of the Neoglaciation were recorded. During this period, a stable sea ice cover formed, and temperatures did not exceed 2.4°C. For the first time, sea surface temperatures in the marginal shelf trough in the western part of the Barents Sea in the period 3.3–9.3 cal kyr BP were reconstructed based on diatom data on the drift sediments.
The colonization of Earth’s land began 2.6 Gyr ago in the Archean, with the emergence of the first terrestrial ecosystems, which were microbial mats (biofilms). This type of land cover lasted until the mid-Ordovician, before plants colonized land. The conception of terrestrial ecosystems during the intermediate stage remains unknown. The findings of Cambrian paleosols are rare, the conclusions on pedogenesis are primarily based on indirect evidences. This work presents the results of studies of Cambrian (495 ± 10 Ma) paleosols, discovered at the top of the weathering crust of the Proterozoic granitic basement (Voronezh oblast). Paleosols are layered crusts on the surface of granite boulders, which are products of the spheroidal weathering of granites. Based on the fossilized biota represented by a community of cyanobacteria, bacteria, and algae, including endolithic varieties, as well as testate amoebae, lichens, and protodiatoms, the objects have been identified as microbial paleosols. Their organic carbon content reaches 0.1–0.5
The manifestations of the Early Capitanian geospheric event in Northeast Russia and its effects on biota, sedimentation, and carbon isotope composition were considered. At the beginning of the Capitanian, a major extinction event occurred, marked by a significant decrease (1.5–2.5-fold relative to pre-crisis levels) in taxonomic diversity across all benthic fauna groups. Concurrently, δ3Ccarb (Omolon Basin) and δ13Corg (Taskan Basin) values decreased markedly. In the Omolon and Taskan Basins, carbonate sedimentation ceased, and deeper-water diamictites and sandy-clayey sediments began to accumulate. The Early Capitanian event was clearly regional and occurred several million years earlier than the Late Capitanian event. For the first time, it has been shown that the event is most likely associated with the activation of island-arc volcanism within the Okhotsk-Taigonos (Koni-Taigonos) volcanic arc, as indicated by a significant increase in the Hg/TOC ratio, considered an indicator of volcanism.
The rare-earth element (REE) distribution in bottom sediments of the Bering Sea northwestern shelf is studied, and the influence of contributing terrigenous provinces and sedimentation conditions is considered. Based on the data obtained, the average REE content (75 ± 22 μg/g) in the sediments studied is significantly lower than the average composition of continental sedimentary rocks and bottom sediments of the East Arctic seas. A genetic link with volcanic rocks of the eastern Koryak Highlands has been established.
