Ашық рұқсат
Рұқсат берілді
Тек жазылушылар үшін
№ 2 (2024)
Articles
Lithological and mineralogical characteristic of the bottom sediments in the areas of ice scouring in the south-western Kara Sea
Аннотация
Sedimentary material sampled in the western Kara Sea both directly in the ice scours and on the background surfaces not disturbed by ice scouring has been studied. Based on the results of research of the physical properties and lithological and mineralogical features of bottom sediments in the ice scours, the bedding depth of the ice gouging impact boundary (ploughing contact) was identified. According to X-ray diffraction analysis of the <0.001 mm fraction, in the samples obtained below this boundary, in contrast to the overlying samples, chlorite has non-heat-resistant structure, which, together with the results of microscopic studies in thin sections, indicates its neoformation. The presence of secondary chlorite in near-surface conditions may be an indicator of the glaciodynamic impact (pressure) of iceberg keels on bottom sediments. The microstructures of the ice scour sediments differ both on the different polygons of the study area and within the same scour, depending on the location of the sampling point on the transverse profile of the morphosculpture.
143-162
Change of solution composition during it migration through the sedimentary cover in the center of the modern hydrothermal system (Juan de Fuca Ridge, Pacific Ocean, Hole ODP 858B)
Аннотация
The article presents the results of studying the change of the composition of the hydrothermal solution during its migration through the Pleistocene sediments from the Hole ODP 858B 38.6 m deep, which was drilled in the northern segment of the Middle Valley of the Juan de Fuca Ridge, in the Dead Dog hydrothermal field, in 20 m from the hydrothermal source with temperature 276°C. The influence of sediments of the Units I, IIB, IID from this hole on the change in the composition of the solution during the solution-sediment interaction has been established. The greatest influence on the composition of the solution occurred during its interaction with the sediments of the Units IIB and IID under high-temperature conditions (200–350°C), which is expressed in the enrichment of the solution with a large amount of chemical elements. A possible change in the composition of the solution is shown in the process of solution-sediment interaction during its migration through the entire sedimentary cover with a thickness of 250–300 m.
163-179
Features of the genesis of manganese ores of the Kvirila deposit, Georgia (according to the data carbon and oxygen isotope composition and rare earth elements geochemistry)
Аннотация
Original data on the isotopic composition (δ13С, δ18О) and geochemistry of major and rare earth elements (REE) in manganese ores of the Rodinauly section of the Kvirila deposit (Georgia) presents in this article. δ13С (V-PDB) values in the carbonate ores vary from –19.6 to –6.6‰, and δ18О (V-SMOW) – from 21.1 to 29.1‰; in the carbonate substance of cement of oxide ores – from –14.9 to –5.5‰ and from 21.8 to 28.4‰, respectively. A feature of the studied ores is the presence in the predominant number of samples (both carbonate and oxide ores) of a negative cerium anomaly (Ce/Ce*PAAS – up to 0.51); there is no pronounced anomaly in europium in them. A conclusion has been made about the formation of ores both under conditions of early diagenesis of sediments and later during catagenesis, which took place with the participation of metal-bearing elision solutions.
180-200
Thermal regime and thermal evolution of the sedimentary cover on Astrakhan oil and gas province
Аннотация
The article considers data on temperatures and heat flow distribution in the sedimentary cover of the Astrakhan swell in the Caspian basin. The calculation of the depth temperatures in two- and three-dimensional model with thermal tomography technology is carried out. The parameters for this calculation were original data on the thermophysical properties of sedimentary cover rocks and on the concentration of long-lived isotopes in rocks. Palinspastic reconstructions of the sedimentation history of the cover served as the basis for calculating the evolution of temperatures over 250 million years.
201-222
(Fe-Ca-Al)-phosphate mineralization enriched with rare earth elements in the sediments of the middle Jurassic paleovalley (Shankinka Occurrence, Moscow Region, central part of the Russian Plate)
Аннотация
A new occurrence of phosphate mineralization – named Shankinka – has been explored in the mouth of the Fed’kovskaya river in the Ruza District of the Moscow region, of which, the most common mineral phases include delvauxite, mitridatite, fluorapatite and crandallite. It has been established that all the Fe-Ca-Al phosphates occurrences in the region are associated with the Bajocian-Bathonian paleovalleys embedded in the Carboniferous rocks and partially filled with Callovian sediments. The structural features of the phosphatization zone as well as its enrichment with Co, Ni, Zn, Cu, and REE indicate a possible link between the Oxfordian organic-rich sediment and phosphate mineralization. It can be assumed that epigenetic phosphate mineralization was a result of the seepage of phosphorus-rich pore waters released from the Oxfordian organic-rich sediment into the underlying Callovian permeable rocks rich in iron minerals.
223-244
Structure, rock types and reservoir properties of altered permian-triassic rhyodacites in the grabens of the Frolovskaya megadepression in Western Siberia
Аннотация
This article presents results of the comprehensive study (composition, reservoir properties, geophysical parameters and age) of altered felsic volcanic rocks (rhyolites, dacites) associated with the Permian-Triassic intermediate structural level of the West Siberian. As a result of secondary alteration, oil and gas reservoirs can form in these volcanic rocks. Taking into account their occurrence depth (more than 2 km), they are available for study only from core and geophysical data. Based on the results of core studies, 25 petrographic varieties of felsic volcanics were established. The combination of such features as 1) structural and textural features, 2) degree of secondary alteration, and 3) peculiarities of logging curves made it possible to group these numerous petrographic varieties into six key rock types. At the same time, the distinguished rock types are characterized by different reservoir properties (porosity, permeability). All 443 samples representing various rock types are characterized by similar geochemical composition, and the U-Pb ages obtained by the zircons (254 ± 2–248.2 ± 1.3 Ma) indicate that the studied felsic volcanics belong to a single tectonic-magmatic stage at the Permian-Triassic boundary. According to seismic data, it was revealed that within the Frolovskaya megadepression (the central part of Western Siberia), the studied volcanic rocks are distributed within grabens. In particular, the boundaries of a relatively large (70 km wide and 200 km long) graben-like Rogozhnikov-Nazym structure were adjusted, and several similar, but smaller structures were identified. A comprehensive analysis of core, log and seismic data made it possible to determine the morphology and spatial relationships of volcanic bodies composed of various types of felsic volcanic rocks, providing the basis for predicting intervals of the section with the best reservoir properties.
245-276