Geofizičeskij žurnal

The «Geophysical Journal» is 45 years old

2024-06-28T16:54:01+03:00

The «Geophysical Journal» is 45 years old

Near-surface air temperature in the Ukrainian Carpathians up to the middle of the XXI century by the EURO-CORDEX models

2024-04-03T13:55:16+03:00

The results of the assessment of future changes in the thermal regime of surface air in the Ukrainian Carpathians for the period up to 2050 are presented in this article. The assessment was performed on the basis of a set of climate indices (mean annual air temperature, number of frost days - FD, number of summer days - SU and number of tropical days - TR) calculated with high spatial resolution (0.05° × 0.05°) based on daily meteorological observations (1960-2020) and the results of 11 regional climate models of the EURO-CORDEX project (2021-2050). To obtain reliable, unbiased projections of air temperature, the model data were bias-corrected using linear scaling and variance scaling. Climate change was assessed based on the calculation of index increments for the period 2021-2050 relative to the period of the current climate 1991-2020. General trends towards an increase in surface air temperature in the region by the middle of the twenty-first century have been detected. Quantitative indicators of such changes: background increases are in the range of 0.35-0.41 °C (or, conditionally, 0.12-0.14 °С·decade-1) for the RCP4.5 scenario, and 0.53-0.56 °C (0.18-0.19 °С·decade-1) for the RCP8.5 scenario. The maximum increases in average annual temperature compared to the period of the current climate in 1991-2020 are 0.56/0.71 °C, respectively, and are confined to the highlands in the southeastern part of the region, i.e., higher warming rates are expected for the highlands. Changes in the threshold climate indices by the middle of the XXI century will have certain spatial differences: higher summer temperatures (SU, TR) are more likely for the northeastern macroslope and the southeastern part of the study area, and in the cold season (FD) of the year, under both scenarios, air temperatures will increase mainly in the northwestern and southwestern parts of the study region.

Geoelectrical inhomogeneities of the lithosphere of the Pripyat-Dnieper-Donetsk basin along the GEORIFT 2013 profile

2024-04-16T11:22:14+03:00

For the first time, for the Pripyat-Dnipro-Donetsk basin, a geological-geoelectrical interpretation of the synthetic model of the distribution of electrical resistivity in the lithosphere along the GEORIFT 2013 profile was carried out on the territory of Ukraine. Geoelectric heterogeneities of the Earth's crust and upper mantle have been revealed based on the generalization of interpretive parameters of various degrees from one-dimensional inversion to two- and three-dimensional models, which are based on experimental observations of the natural low-frequency electromagnetic field of the Earth. The connection of electrical conductivity anomalies with structural features, which were revealed according to the data of the DSS along the profile, was established. The nature of anomalous electrical conductivity is considered on the basis of a complex analysis of geological and geophysical data, and geoelectrical criteria for the selection of promising areas of hydrocarbon deposits are formulated.

The unique distribution of resistivity by depth corresponds to the subvertical contact zone of longitudinal wave velocities, which manifested itself in the interruption of the tracing of the boundaries interpreted according to refracted and/or reflected P-waves. This zone corresponds to a complex knot of tectonic structures: the Kherson-Smolensk transregional tectonic seam, deep Kirovohradsk and Pereyasliv-Khmelnytskyi-Pryluksky fault zones. The coincidence of the depth of the anomalous distribution of electrical conductivity with the zones of low velocities spatially corresponds to tectonic disturbances, such as (from west to east): the Western Kryvorizko-Kremenchutsky thrust, the Kryvorizko-Krupetsky and Kryvorizko-Kremenchutsky deep fault zones.

In the joint interpretation of seismic and electromagnetic sounding data, the structural approach is more often used, which increases the informativeness of depth research. It is shown that the zones of high electrical conductivity, which coincide with the zones of low velocities, are caused by the presence of fissures and the saturation of rocks with deep fluids, which must be considered as ways of their migration to the upper horizons of the earth's crust, where they become an important source for all subsequent processes of the formation of oil and gas deposits.

Geological facts, geological judgments, geological truth and the State Geological Map of the Ukrainian Shield

2024-02-22T13:55:03+02:00

The shortcomings of the Geological maps in Ukraine and maps of the minerals of the crystalline basement of the Ukrainian Shield of the State Geological Map of Ukraine (scale 1:200 000) published in Ukraine are considered in terms of their compliance with modern views on the structure and development of the Earth's crust in the Early Precambrian (Archean-Early Proterozoic). It is shown that, despite the basic requirement of the Early Precambrian Section of the National Stratigraphic Committee of Ukraine that the Precambrian formations of the Ukrainian Shield should be age-divided based mainly on isotopic geochronology, this did not become the basis for the preparation of geological maps. Some authors and editors of maps have not gotten rid of the influence of the outdated concept of the formation of early Precambrian strata by their successive layering and fixing this sequence in the vertical section of the earth's Scrust during regional metamorphism. The determining role of horizontal crustal movements, plume and plate tectonic processes was also perceived ambiguously. The role of large-scale thrusts and subductions of lithoplates, which changed the age relationships of rocks in the section, was not taken into account. The article compares tectonic schemes and sections to geological and mineral maps of the crystalline basement of the Ukrainian Shield with maps of the Precambrian basement of the South African, Canadian, and Western Australian Shields, in which the legends replace the principle of "lower-higher" with the principle of "older-younger" based on isotopic dating. It is shown how the views of Western geologists have evolved from the mid-twentieth century to the present day in the study of the Archaic Barberton Greenstone Belt (eastern margin of the Kaapvaal Craton, South Africa), which has long been building geological map legends on the basis of highly accurate isotopic data.

The disadvantage of the published Geological maps and mineral maps of the crystalline basement of the Ukrainian Shield at a scale of 1:200,000 is also the presence of a large number of inconsistencies in the author's interpretation of the geological content of different, and even neighboring by nomenclature, map sheets, especially tectonic schemes and sections, and designations of the material composition of rocks.

The authors of the article propose to return again to the discussion and solution by geologists and geological organizations of the issue of compiling a New series of Geological maps and mineral maps of the crystalline basement of the Ukrainian Shield at a scale of 1:200,000 on the basis of previous and new geological, geophysical and geochemical data obtained over the past 20 years and the latest achievements of world geological science.

Key words: Ukrainian Shield, isotopic geochronology, geological maps, tectonic schemes, faults, tectonophysics, geological truth.

Probabilistic characteristics of the freeze-up duration on the rivers of the Prypiat basin within Ukraine

2024-02-22T14:15:28+02:00

The freeze-up those forms on rivers in the autumn-winter period significantly impacts on the hydrological, hydrochemical, biological processes of rivers, as well as the work of hydropower, shipping, fisheries, etc. In modern conditions, the formation, duration, and break-up of freeze-up on rivers occurs under the influence of natural, anthropogenic factors and climatic changes. Therefore, the research of modern trends of the freeze-up duration on the river and the determination of its calculation characteristics is an urgent task. Traditionally, the multi-annual mean, minimum and maximum values of the freeze-up duration on rivers are determined. Such indicators are important, but they still provide a rather limited knowledge about the freeze-up over a period of time. Expand knowledge about the variability, magnitudes, duration, dates of appearance freeze-up and break-up can by determining its probabilistic characteristics, but such research have not been carried out for the rivers of Ukraine, including for the rivers of the Prypiat basin.

The objective of this paper is to determine the probabilistic characteristics of the freeze-up duration of the rivers of the Prypiat basin within Ukraine, as well as the analysis of the obtained results.

The data of 29 water gauges were used for the period from the beginning of observations to 2020, inclusive. As statistical parameters of the analytical distribution of the freeze-up duration, the multi-annual mean value, the coefficient of variation and the coefficient of asymmetry were used. The Pearson distribution of type III was used to created analytical curves of the freeze-up duration, and the Weibull formula was used for the empirical distribution of the freeze-up duration.

In this paper, the probabilistic characteristics and statistical parameters of the freeze-up duration on the rivers of the Prypiat basin within Ukraine are determined. The probability distribution of Pearson type III quite satisfactorily describes the empirical points of the freeze-up duration on the rivers of the Prypiat basin within Ukraine. The vast majority of the analytical curves of the distribution of the freeze-up duration have a negative asymmetry. Only 8 the analytical curves have a positive asymmetry. In the Prypiat Basin within Ukraine the multi-annual mean of the freeze-up duration is 69 days and ranges from 26 to 95 days. The values of the asymmetry coefficients are small and vary from 0.01 to 1.02 for positive values and from -0.03 to -0.60 for negative values. The coefficients of variation change within small limits from 0.34 to 0.79.

Probabilistic characteristics can use for the design and operation of any hydrotechnical structures, as well as the work of economic sectors that are related to the use the rivers. In addition, the research results can be used for further research, namely any search for prognostic dependencies, generalizations, zoning, etc.

Material balance of metamorphic transformations of coal seams and their dangerous properties

2024-03-12T14:39:23+02:00

Purpose: To establish empirical relationships during coalification of coal seams between the main components of the organic (combustible) mass, moisture content and mineral impurities using experimental data on the consumer qualities of solid fuels obtained by generally accepted standard methods. Reliably established relationships between these main components make it possible to scientifically substantiate and reveal the nature of the occurrence of dangerous properties of coal seams during mining operations due to the factor of metamorphic transformations and the generation of gaseous and liquid products.

The research methodology was developed based on the results of a preliminary analysis of the change in the ratio between the main components of organic (combustible) mass, the content of moisture and mineral impurities during coal formation, starting from the processes of peat formation and subsequent coalification. Experimental data on the consumer qualities of solid fuels determined by generally accepted standard methods were used.

Results: At all stages of metamorphic transformations of coal seams, with an increase in carbon content, a unilateral reduction in the elemental oxygen content in the organic (combustible) mass has been established. This indicates the formation of gaseous products at all stages of metamorphism with the participation of carbon and oxygen of the organic (combustible) mass. The reduction in the elemental content of hydrogen, nitrogen and organic sulfur in the later stages of metamorphism indicates the participation of these components in the generation of gaseous products.

The reliability of the empirical dependence of carbon content on the average reflectivity of vitrinite was tested.

The generation of moisture at the stage of metamorphic transformations of coals was not fully confirmed by the direction of trends in the average content of moisture, oxygen and hydrogen at successive stages of the processes of peat formation, diagenesis and metamorphism up to the transition from hard coals to anthracites.

A significant excess (up to two times) of the yield of volatile substances was established compared to the content of the sum of the main components of the organic (combustible) mass at fixed values of carbon content.

Scientific novelty: Based on changes in the ratio of the elemental content of the main components of the organic (combustible) mass (solid residue), their participation in the formation of gaseous products at all metamorphic stages of transformation of coal seams has been established. The obtained results of the formation of the material balance make it possible to introduce appropriate clarifications into the scheme of coal formation processes in terms of the generation of specific gaseous products at each stage.

Practical value: The practical significance lies in the need and possibility of improving the regulatory framework for the safety of mining operations when forecast the hazardous properties of coal seams.

Search for fresh water at the border of the Priazov megablock and the Donbas

2024-06-19T11:31:20+03:00

The article presents proposals for improving the methodology and the results of reinterpretation of geoelectrical works in the Donetsk region to refine the surveyresults for underground water exploration, carried out by the «Dniprogeofizika» trust in the 1970s. In the following years, the territory was covered by large-scale gravimetric surveys during the search for various minerals. The authors performed a complex processing and reinterpretation of the available geophysical materials to identify rock-loosening zones based on gravimetric data and assessed the results’ applicability to the study of promising areas for the search for groundwater in modern conditions. A complex analysis of electrical reconnaissance materials showed the effectiveness of their reinterpretation using the data of large-scale gravimetric surveys. The gravimetric maps made it possible to correlate in more detail the tectonic disturbances with local dips detected on individual profiles and areas according to the results of vertical electric probing, and to build a general geological and tectonic framework in which discontinuous disturbances and zones of their densification were harmoniously integrated into the contours of the distribution of sedimentary deposits. Analysis showed that the more detailed the gravimetric survey, the more accurately geological and tectonic inhomogeneities in the upper part of the sedimentary cover are mapped. The use of a database of field gravimetric surveys of various years and scales allows to significantly increase the efficiency of work and reduce the economic costs of underground water searches during the selection and localization of search areas of the first and second stages. The obtained results and the developed improved method of interpretation are proposed to be used when determining the points of water intake wells, not only in the zone of where the Folded Donbass borders the Azov megablock (crystalline massif) of the Ukrainian Shield, but also in places subject to anthropogenic impact.

Geological conditions for the development of geothermal energy in Azerbaijan

2024-06-17T18:16:04+03:00

The article considered the thermal waters existing in Azerbaijan, the prospects for their use, business opportunities and other issues. Forecast operational reserves of thermal waters in the Republic, renewable energy potential of Azerbaijan, including the share of renewable energy in Azerbaijan in 2020 are reflected here. Thus, there are a large number of closed and unused exploration wells that can be restored and used to generate geothermal energy with less investment. Now the main goal is to determine the optimal location for drilling wells with a higher geothermal potential and the problems of using this energy. Thermal waters with different chemical composition and mineralization in Azerbaijan are predominantly common in the fold regions of the Caucasus and Talysh Mountains and have significant reserves. As a result of research conducted on more than 1,000 thermal water sources in Azerbaijan, it was determined that the total reserve of thermal water is more than 245´10³m³/day. The main discharge paths of these waters are tectonic faults of different directions and amplitudes. The gas content of the thermal water sources of the Greater Caucasus and Talysh mountains are methane, nitrogen, hydrogen-sulfur mixture, and the content of the Lesser Caucasus’ are mainly carbon dioxide. Methane waters are usually high-pressure and high-flow, and high-temperature (64—95 °C). The number of sources containing methane is up to 200. Such sources include Masalli (Arkivan), Devechi (Ledzh), Salyan (Babazanan) and others. Sources of nitrogen are found in the southern part of the Greater Caucasus and in Talysh. These include both cold (14—180 °С) and hot (41—550 °С) springs. The highest nitrogen content among them is Alasha — 100 % (Astara), Meshesu 100 % (Lankaran), Ledzh — 37 %, Khaltan — 88 % (Devechi).

Besides (in addition), in the article the recent use of low-potential geothermal energy, the issues of application of new technologies in the development and management of geothermal resources also reviewed.

Determination of changes in the degree of salinity of the marine water environment by acoustic methods

2024-06-17T18:26:02+03:00

Given the pressing need to address the escalating water supply challenges in the coastal regions of southeastern and southern Ukraine, the expansion of methodologies for identifying zones of submarine groundwater discharge (SGD) within the Ukrainian shelf of the Azov-Black Sea basin stands as a paramount task for national marine hydrogeologists and geoecologists. Consequently, the advancement of novel comprehensive methodologies and technologies for locating additional freshwater reservoirs specifically, the segment of groundwater outflow into the Black Sea geo-ecosystem (GES), holds immense potential to broaden the horizons for water provisioning to the populace and other stakeholders (such as agricultural entities, industrial sectors, etc.) across the coastal areas of Ukraine.

The article presents theoretical findings on the feasibility of using acoustic methods to detect changes in salinity of the marine aquatic subsystem (MASUS) within geo-ecosystem (GES) of the sea basin, particularly in areas where freshwater discharge from geological aquifers or riverbed runoff is probable. To achieve this objective, we examine the unique characteristics of acoustic signal reflection as it propagates through the MASUS water environment, analyzing variations in sound speed corresponding to changes in salinity within the marine water environment. Theoretical calculations employ methods from statistical physics and quantum mechanics to investigate such phenomena.

The comprehensive theoretical insights outlined in this article enable us to propose a practical and cost-effective approach for identifying sources of submarine groundwater discharge. This method combines two acoustic techniques: measuring sound speed within the MASUS water environment and assessing the reflection coefficient of an acoustic signal from the interface between MASUS water and the geological environment of GSUS GES within the marine basin.

Novel interpretation of the crustal structure and hydrocarbon evolution within the South Caspian and Kura sedimentary basins, Azerbaijan

2024-06-17T18:34:55+03:00

The South Caspian Basin, Lower and Middle Kura Basins, onshore Azerbaijan, and Georgia Upper Kura Basin are a genetically linked basin system created in a Mesozoic extensional setting with a complex Cenozoic sediment fill history. Delineating these basins shed new light on understanding the complex geodynamic history of the region between the Black Sea and the Caspian Sea and elucidate the petroleum prospectivity of the region.

Key data used for basin analysis were a series of regional isopach maps, temperature measurements from over 150 onshore and offshore boreholes in Azerbaijan, derived geothermal gradient data, and published surface heat flow data. Taken together, they allowed us to put some constraints on the crustal structure of an area where accurate temperature measurements are limited. An integrated set of offshore and onshore regional isopach maps for the key stratigraphic units from Jurassic to Pleistocene were created. The depth to basement and the crustal thickness across four seismic cross-sectionswere estimated and validatedvia interpretation of isopach maps and gravity and magnetic modeling.

The results encompass the area from the onshore Kura Basin in eastern Georgia to the offshore South Caspian. Several specific regions were differentiated, including a «cold» region in the South Caspian Basin. A reasonable correlation was established between basement depth, crustal thicknesses, and geothermal gradients. The tectonic boundary between these two basins controls the geothermal gradient change and therefore the hydrocarbon potential.

The western margin of the South Caspian Basin represents a long-standing crustal boundary between the South Caspian Basin oceanic crust of the South Caspian Basin and the thicker crust of the Kura basin of the island-arc origin. The Mesozoic evolution of these basins started as a result of an island arc extension in Mesozoic, followed by Cenozoic flexural overprint with rapid burial and significant sediment flux, thus creating suitable conditions for the development of a dynamic petroleum systems in the South Caspian Basin.