The ideas about the content of the concept of “geoecological space”, types, scientifi c content and applied tasks, types of systems studied by geoecology, theoretical foundations of which are developed on the basis of the concept of environmental functions of abiotic spheres of the Earth are characterized. Types and groups of indicators used to assess geoecological conditions.
The division of deposits by types of hydrocarbons on the territory of the West Siberian Plate allowed us to identify three areas: Yamalo-Gydan, where gas and gas condensate fields are concentrated, Nadym-Taz with a mixed type of deposits and the Latitudinal Ob region, where oil fields predominate. These areas are confined to certain neotectonics areas. Comparison of the location of hydrocarbon deposits with the latest structures allowed us to establish signs of their localization both within each of the regions and in general for the territory of the West Siberian Plate. It is recorded that oil and gas fields are confined mainly to the areas of the newest regional inherited depressions, faults with a shear component of the northwestern and northeastern strike, areas with high (66–100%) and low (0–33%) lineament density, depressions-valleys separating the newest regional and local structures and the boundaries of local uplifts and depressions.
The study area occupies the southwestern part of the Indian Ocean, where the Mozambique and Madagascar ridges are located. Ideas about the tectonic structure of these ridges are still debatable. The anomalous structure of the crust of these ridges can be explained either by underplating — thickening of the oceanic crust from below due to magmatism, or by stretching and thinning of the continental crust. Based on the data on anomalous gravitational and magnetic fields, seismotomography, and other geological and geophysical information, density modeling was performed for four profiles, which revealed differences in the crustal structure and evolution of the Mozambique and Madagascar ridges.
The paper presents the results of studying the lithochemical features of the Late Jurassic-Early Cretaceous tuff-terrigenous rocks of the Ust-Belsky and Algan terranes. Tuff-terrigenous rocks represented by medium-fine-pelitic-grained quartz-feldspar and feldspar greywackes. According to the results, they were formed due to the erosion of intermediate and basic composition volcanic formations, in the marine environment, near the coast. The main source was associated with the island arc in the northwest of the region. Tuff-terrigenous rocks of Ust-Belsky terrane formed in different parts of the forearc basin. Tuff-terrigenous rocks of Algan terrane formed in the trenchslope basin.
Zircons from the Early Carboniferous granitoids of the Neplyuevkа massif of the South Urals have been dated (SHRIMP). Two different age groups are distinguished among the studied zircons: 1 — from 334 to 342 Ma; 2 — from 354 to 356 Ma. The older ages probably correspond to the time of zircon crystallization from the melt, while the younger ages resulted from a partial loss of radiogenic lead by zircon during the cooling of the massif or from thermal impact of Early Carboniferous or even Early Permian intrusions. The formation of the Neplyuevkа complex at the very beginning of the Carboniferous marks the most important stage in the geodynamic evolution of the Southern Urals — a rapid transition from island arc magmatism, which continued during Devonian, to riftogenic magmatism, which ended only in middle Visean.
As part of this work, various sedimentation environments were identified in the Middle-Late Jurassic (J2k–J3v1) on the territory of the Krasnoleninsky arch in Western Siberia. The heterogeneity of the seabed topography and the presence of islands formed by protrusions of the pre-Jurassic basement led to the formation of the Vogulka strata as a result of the removal of clastic material from the land. At the same time, far from the islands, in relatively calm shallow environments, clayey and glauconite-clayey sediments of the Abalak Formation accumulated. Gravelites and sandstones of the Vogulka strata were formed unevenly. The greatest thickness of these deposits is observed to the west of the central upland. The difference in the thickness of clastic strata on the western and eastern slopes could probably be caused by the specific horseshoe shape of the island and the absence of active currents on the western part of the slope, as well as its greater steepness. The upper member of the Vogulka strata, composed of detrital limestones, is extremely thin (no more than 1 m), and contains numerous unconformities. Probably, these traces of erosion can be indirect evidence of the influence of the Late Oxford regression on the structure of the section, which was previously noted in adjacent territories.
Some aspects of the genesis of industrially important Paleozoic epithermal gold deposits of the Omolon massif are considered. According to the results of Ar-Ar dating of ores, their age is 20–30 Ma younger than that of the volcanic complexes of the Kedonian volcanic belt of the Devonian, with which this mineralization is traditionally associated. For the Paleozoic continental marginal magmatism of the Omolon massif, we have identified a stage of post-subduction rifting, characterized by the formation of volcano-plutonic associations of shoshonite-latite series. The authors suppose that it was at this stage, the chronological boundaries of which are determined as 335–286 Ma, that the ores under consideration were formed. The paragenetic connection with riftogenic shoshonite-latite series explains such specific features of the Paleozoic epithermal gold mineralization of the Omolon massif, such as high gold-silver ratio, low ore sulfide content, widespread development of fluorite and tellurides, low values of the primary Sr isotope ratio (0,703–0,706).
The Golets Vysochaishy deposit has a sub-tabular orebody hosted by black carbonaceous fine-grained aleuropelitic rocks. We have studied fluid inclusions in quartz samples taken from sulfide-quartz veins in the ore zone of the deposit — performed studies made it possible to establish the parameters of the ore-forming fluid. Thus, the fluids of the deposit are characterized by the typical features of orogenic vein gold deposits’ ore-forming fluids. The process of carbon dioxide degassing from the fluid may have contributed to the deposition of native gold.
Based on a comparison of the chemical composition and a number of petrophysical and thermodynamic parameters of changed to varying degrees syn-ore and post-ore Devonian gabbroids of the Dzhusa pyrite-polymetallic deposit (South Ural), the principal possibility of quantifying the grade of their alteration and transformation related with the hydrothermal post-volcanic and dynamic metamorphism is shown.
The paper presents the results of coal petrographic and geochemical studies of the Tutleim Formation rocks organic matter in the area of the Em-Egovskaya summit. Five macerals were identified that compose the organic matter of the studied formation: “standard” bituminite, “atypical” bituminite, radiolarian organic matter, alginite and vitrinite, as well as bitumen and bitumen films, which are the products of the original organic matter transformation. The metamorphosis in macerals during catagenesis is described, and the order of their entry into the generation phase is established. It has been shown that alginite starts transforming first, then “standard” bituminite, “atypical” bituminite, and the last one is the radiolarian organic matter. The results obtained were confirmed by the laboratory modeling of the further organic matter transformation. New bitumens are formed with different fluorescent properties compared to the initial ones. The results obtained in combination with the study of changes in the composition of both macerals and bitumen can make it possible to assess the contribution of individual organic matter microcomponents to the process of petroleum hydrocarbons generation.
The article provides the results of the hydrocarbon compounds (HCS) molecular composition in open and closed pores of the Bazhenov horizon source rocks studying. Extraction with solvents of different polarity allows to withdraw additional HCS from both open and closed pores of rock samples, and their composition systematically differs both in the distribution of normal alkanes and in the values of biomarker parameters characterizing the maturity and sedimentary conditions. HCS in open pores is more thermally maturated than HCS in closed pores, and in both cases, maturity can decrease in blocked pores, especially in those sealed with soluble in alcohol-benzene resins-asphaltenes. The values of parameters Pr/Ph and dia/(dia+reg)C27 are higher for bitumen in open pores, but the values of C29/C30 and H35S/H34S are much higher for bitumen in closed pores, and can vary in blocked pores with respect to the open ones. As a result, a improved model of HCS distribution in the pore space was proposed, which shows the presence of residual light HCS in open pores, as well as two types of blocked pores, in which HCS are sealed by different resins-asphaltenes in both open and closed pore spaces.
The Bazhenov Formation rocks contain thin luminescent layers enriched in type I kerogen, which is unique for the bulk of the organic matter of the Bazhenov Formation of the West Siberian petroleum basin. The article provides a detailed characterization of the mineral and organic parts and proposed origin of these layers, called by the authors “alginite-rich layers”. The wide distribution of the luminescent alginite-rich layers over the central part of Western Siberia in a single stratigraphic range allows them to be used as marking horizons, as well as for assessing the thermal maturity of kerogen. This study contributes to understanding the diversity of processes that form the organic-rich deposits of the Bazhenov Formation.
Properties of unconventional prospective deposits are interconnected by the rocesses of reservoir formation and oil and gas formation. Dispersed dolomite in situ formed during the maturation of TOC from syngenetic magnesium in the rock matrix increases the void space of the rock, thereby forming an unconventional reservoir filled with autochthonous hydrocarbons and oil components. In the process of TOC maturation and hydrocarbon migration, the TOC components are redistributed in the void space, thereby, the released volume of rocks is filled with stationary resinous asphaltene substances, which sharply reduces the reservoir properties of unconventional reservoirs. As a result, the definition of “organic” porosity includes a broader concept than just the porosity of kerogen. This is a more complex physicochemical process of transformation of the organic matter itself and the redistribution of elements within the formation as a result of the maturation of TOC components and hydrocarbon migration. When assessing the oil and gas potential in the section, we distinguish three groups of rocks: unconventional reservoirs with an increased TOC content and the presence of mobile hydrocarbons; bituminous rocks, in which part of the pore volume is filled with resinous-asphaltene substances and host dense carbonate rocks without organic matter. Also, sporadically developed traditional reservoirs are distinguished throughout the section of the Domanik type of rocks.
The article presents the results of the interpretation of magnetotelluric soundings performed in the Southern Ladoga region. When performing the 3D inversion, both new data obtained by the LADOGA working group in 2018–2021 and data from the profile 1-EV (the “Loop” section) worked out in the early 2000s were used. Based on the results of automatic inversion performed in the ModEM program (Egbert and Albert), a three-dimensional geoelectric model of the earth’s crust to a depth of 60 km is constructed, which shows the complex heterogeneous structure of the studied territory.
In the geoelectric model, two anomalous zones of core electrical conductivity of the south-eastern and north-eastern directions are distinguished, the first of which is a continuation of the well-known Ladoga anomaly. The presence of the second conducting structure confirms the results of single magnetovariational sounding performed by Igor Ivanovich Rokityansky in different parts of the East European Platform in the early 80s of the last century.
The registration possibilities of the new broadband seismic station “Aleksandrovka” are considered. It has been established that its hardware and installation conditions make it possible to monitor the central part of the East European craton in order to identify events of small magnitude and to clarify the coordinates of located events. It is shown that the criterion for recognizing the genesis of events, developed earlier for the MSG “Mikhnevo”, can be applied to the records of a single seismic station.
