Geodynamic Conditions Research Articles

ИССЛЕДОВАНИЕ ПРИРОДЫ СЕЙСМИЧЕСКИХ СОБЫТИЙ В РАЙОНЕ ПХГ ПРИВОЛЖСКОГО ФЕДЕРАЛЬНОГО ОКРУГА

Seismicity during UGS operation had not yet been known in Russia. This work presents studies on the manifestation of seismicity in the area of three underground gas storages (UGSs) located in the south-eastern part of the East European Platform (European part of Russia). The tectonic structure of this region, geodynamic conditions and technological characteristics of «Vostochnoye», «Zapadnoye», «Uzhnoye» UGS are presented. An analysis of the situation with the manifestation of seismicity allows us to conclude that it is technogenic in nature, a feature not previously noted on Russian UGSs. There is a wide list of signs indicating the relationship between the mode of operation of UGSs and the nature of seismicity: prior to the start of UGS operation technogenic seismicity in this area was not known; there is a clear correlation between UGS operation and seismicity; the epicenters of seismic phenomena are located in the geodynamic influence zone of the UGS; in the region there are Earth crustal faults that experienced activation in late Cenozoic time and respond to strong earthquakes of neighboring tectonic areas, which consequently indicates their predisposition to reactivation; the change in pressure in the UGS reservoir is sufficient to induce seismicity. The phenomenon of increasing seismic activity during the gas extraction period is noted, which is explained by the effect of softening of the containing massif and its subsequent push-like deformation when the gas pressure in the reservoir is reduced. Despite the weak seismicity, which does not pose a threat to UGS facilities and adjacent territories, it is proposed to include seismic observations in the complex geodynamic monitoring at Russian UGS to establish patterns over a long period of time.

Grain-scale zircon Hf isotope heterogeneity inherited from sediment-metasomatized mantle: Geochemical and Nd-Hf-Pb-O isotopic constraints on Early Cretaceous intrusions in central Lhasa Terrane, Tibetan Plateau

AbstractClarifying the mechanism of recycling of pre-existing continental crustal materials into the source of mantle-derived magma is a challenging effort that can be of great value to improving our understanding of mantle processes and continental crust growth. This study presents an integrated investigation of whole-rock and mineral geochemical and Nd-Hf-O-Pb isotopic data for dolerites and diorites intruded in the central Lhasa Terrane of Tibetan Plateau at ca. 120 Ma (zircon U-Pb ages). These intrusions have similar distributions of trace elements that are characterized by depletion in Nb-Ta relative to Th, Ba, and U, and moderately negative whole-rock εNd(t) (–5.0 to –1.7) values. Magmatic zircon shows dramatically variable εHf(t) values (from –5.0 to +13.7 in the same rock, including up to 12 epsilon unit variability in single grains). On the other hand, the zircon δ18O values are relatively uniform (+6.0‰ to +7.7‰). The constant 208Pb/206Pb values of clinopyroxene crystallized at ca. 500–900 MPa suggest no contamination with lower continental crust. The lack of covariation between Hf and O isotopes from the same grains, and the lack of relationship between Hf isotopes and trace elements (e.g., Hf, Th/U, and Yb/Gd) in the magmatic zircons, together with the absence of ancient zircon xenocrysts, imply limited upper crustal contamination. In combination with high-whole-rock Th/La (>0.29) ratios, we interpret the zircon Hf isotope heterogeneity as inherited from a depleted asthenospheric mantle with the addition of 1–4% Hf from isotopically heterogeneous sediments. Our study therefore emphasizes the need for caution when using complex Hf isotopic zonation in zircon as an argument for intracrustal hybridization of two end-member magmas derived from distinct reservoirs. In addition, the high-Zr/Y ratios and no negative Zr-Hf anomalies of the Aruo intrusions imply a high surface temperature of the down going slab that was able to fully dissolve zircons in the subducted sediments. This requires a special geodynamic condition that was most likely related to the steepening of flatly subducted Neo-Tethyan lithosphere at ca. 120 Ma according to a synthesis of regional tectonic-magmatic-sedimentary records.

Subduction and Slab Detachment Under Moving Trenches During Ongoing India‐Asia Convergence

AbstractThe dynamics of slab detachment and associated geological fingerprints have been inferred from various numerical and analog models. These invariably use a setup with slab‐pull‐driven convergence in which a slab detaches below a mantle‐stationary trench after the arrest of plate convergence due to arrival of continental lithosphere. In contrast, geological reconstructions show that post‐detachment plate convergence is common and that trenches and sutures are rarely mantle‐stationary during detachment. Here, we identify the more realistic kinematic context of slab detachment using the example of the India‐Asia convergent system. We first show that only the India and Himalayas slabs (from India's northern margin) and the Carlsberg slab (from the western margin) unequivocally detached from Indian lithosphere. Several other slabs below the Indian Ocean do not require a Neotethyan origin and may be of Mesotethys and Paleotethys origin. Additionally, the still‐connected slabs are being dragged together with the Indian plate forward (Hindu Kush) or sideways (Burma, Chaman) through the mantle. We show that Indian slab detachment occurred at moving trenches during ongoing plate convergence, providing more realistic geodynamic conditions for use in future numerical and analog experiments. We identify that the actively detaching Hindu Kush slab is a type‐example of this setting, whilst a 25–13 Ma phase of shallow detachment of the Himalayas slab, here reconstructed from plate kinematics and tomography, agrees well with independent, published geological estimates from the Himalayas orogen of slab detachment. The Sulaiman Ranges of Pakistan may hold the geological signatures of detachment of the laterally dragged Carlsberg slab.

The mechanism of formation and prospects of non-structural traps in the South Caspian megadepression


 
 
 The article examines the geodynamic conditions for the formation and distribu- tion of non-structural traps in the oil and gas regions of Azerbaijan, such as the interfluves of the Kura and Gabirri, Yevlakh-Aghjabadi, Ganja, Lower Kura, the Baku archipelago, Shamakhi-Gobustan and Absheron. For this purpose, the surfaces of the Baikal basement, Mesozoic and Maikop deposits of the region were modeled and analyzed. The modeling revealed a submeridional uplift (positive tectonic element) that began to develop in the Maikop between the Kura and South Caspian basins. This has strongly influenced the folding and especially the formation of non-structural (tectonically sealed, lithologically limited, stratigraphic unconformity-associat- ed) traps in the region. As a result of the analyzes, we clarified the geotectonic characteristics of the formation of non-structural traps (tectonically sealed, lithologically limited, stratigraphic unconformity-associated) and compiled their distribution maps based on them. The analysis of these maps makes it possible to substantiate the features and reasons for the formation and distribution of non-struc- tural traps in the region. Thus, tectonically sealed traps were formed mainly in the oil and gas-bearing areas of the Kura and Gabirri interfluve, the Lower Kura, Shamakhy-Gobustan, Absheron and Baku archipelago, which are not only located in an active geotectonic zone, but likewise, the geological section of these oil and gas-bearing regions (OGBR) significantly differs from the Yevlakh-Aghjabadi and Ganja clay composition (clay rocks), and therefore, high parameters of the development of mud volcanism and clay diapirism are seen in the area. By contrast, in the Yevlakh-Aghjabadi and Ganja oil and gas regions, mainly effusive rocks have developed, which have incompetent properties and resist geotectonic – tangential-horizontal-compressive forces. Formed in this part of the region, thetraps associated with lithological wedging out have been mainly formed by covering the effusive or relief ledges. It should be noted that quantitatively, the traps with stratigraphic unconformity are developed relatively poorly and coincide with the distribution of lithologically wedge-out traps. The aim of the study was answ
 
 

Vendian age of igneous rocks of the Chamberlain valley area (Northern part of the Wedel Jarlsberg Land, Svalbard Archipelago)

The geological structure, structural relations with the underlying complexes, mineral composition, age and origin of sedimentary-volcanogenic and intrusive formations of the Chamberlain valley area (northern part of the Wedel Jarlsberg Land, Svalbard Archipelago) are considered. As a result of the studies, two stages of the Late Precambrian endogenous activity in this area have been identified. For the first time the Vendian ages (593-559 Ma) of intrusive (dolerites) and effusive (basalts, andesites, tuffs) rocks were determined by U-Pb-method (SHRIMP-II) for Svalbard Archipelago. At the same time, the Grenville ages for large bodies of gabbro-diorites, metadolerites bodies (1152-967 Ma), and metagranites (936 Ma) were determined for the first time for this area, which correlates well with the ages of magmatic formations obtained earlier in the southern part of Wedel Jarlsberg Land. A detailed petrographic and petrochemical characterization of all the described objects were compiled and the paleotectonic conditions of their formation were reconstructed. Based on these data, the Chemberlendalen series, which is dated to the Late Vendian, and the Rechurchbreen series, which the authors attribute to the Middle Riphean and correlate with the lower part of the Nordbucht series are distinguished. The data obtained indicate a two-stage Precambrian magmatism in this area of the Svalbard archipelago and, most importantly, provide evidence for the first time ever of endogenous activity on Svalbard in the Vendian time. This fact makes it possible to reconsider in the future the history of the formation of folded basement of the Svalbard archipelago and the nature of the geodynamic conditions in which it was formed.

Voznesenskoe gold ore deposit (Southern Urals): Geological structure, ore-bearing rock geochemistry, geodynamic formation conditions

Research subject. The geological structure, petro-geochem ical features of the ore-bearing rocks of the Voznesenskoe gold ore deposit (Southern Urals) and the geodynamic conditions of its formation. Methods. The content of petrogenic oxides was determined using silicate analysis; rare elements were determ ined using ICP-MS methods by an EIAH 9000 mass spectrometer and ICP-AES by an ICPE-9000 mass spectrometer. Results. The Voznesenskoe deposit is confined to a fragment of the crustal part of the section of harzburgite-type island-arc ophiolites. The ophiolite section is composed of taxite gabbroids, a sequence of dolerites, basalts, basaltic andesites and their tuffs, in places separated from gabbroids by lenses of serpentinites, and a package of subparallel dikes of porphyry gabbro-dolerites, gabbro-diorites, and diorites. Volcanics and dyke rocks with normal alkalinity and tholeiitic composition exhibit the geochemical characteristics of suprasubduction formations. In terms of chemical composition, they are comparable to the volcanic rocks of the pyritebearing complexes of the Baimak-Buribaevskaya Formation (D1e2). At the same time, the Voznesensky rocks have a number of distinct features, which are likely to be related to the geodynamic setting of their formation. In particular, ore-bearing effusive rocks and dykes differ from volcanic rocks of pyrite-bearing complexes in terms of a higher titanium content, the absence of boninite and silicic volcanic rocks, as well as the predominance of porphyry rock types. Conclusion. The conducted analysis of geochemical data using the V-Ti/1000 and LaN/SmN-TiO2 diagrams suggests that the association of mafic volcanic rocks and ore-bearing dykes of gabbro-dolerites, gabbro-diorites and diorites of the Voznesensky deposit was formed in the back-arc basin of the Late Ems frontal island arc.

Influence of structural-geodynamic systems on formation and distribution of hydrocarbon potential of the Black Sea-Caspian region

The article considers the results of the reconstruction and analysis of the geodynamic conditions for the formation of the main elements of their structure in the Black Sea-Caspian region, expressed in the features of the distribution of its structural-geodynamic systems of different ages. As structural-geodynamic systems, sets of elements of the block and zonal structure of the upper part of the earth's crust (basement and sedimentary cover) are considered, united by the same type (general) reaction from an external or internal source of tectonic energy in relation to the system during a certain phase of tectogenesis. The results of the research indicate that the predominantly offshore deep-water Black Sea and South Caspian provinces are controlled by tectonic megadepressions formed in the Alpine and recent epochs of tectogenesis. At the same time, both provinces include in their internal structure both elements that arose at different stages of Alpine and recent structure formation, and fragments of older plate and folded structures, reworked in these epochs and buried under Cenozoic or Cretaceous-Cenozoic deposits, to varying degrees. The latter, in turn, partially or completely control the position and configuration of the oil and gas regions within these provinces. Keywords: structural and geodynamic systems; sedimentary basins of different ages; oil and gas source strata; prospects for oil and gas potential; phase composition; hydrocarbon potential.

Neotectonic structures and modern geodynamics of the middle flow region of the Don river (the territory of the Novovoronezh nuclear power plant)

Background. Structural and geodynamic studies are conducted in the region of the middle flow of the Don river.Aim. An identification and evaluation of neotectonic structures, determination of geodynamic conditions for their formation and an analysis of intensive exogenous geological processes in connection with the need to ensure the safety of the Novovoronezh nuclear power plant (NPP) located in this area, the largest in the central part of the Eastern European platform.Materials and methods. According to the concept of deep geodynamic systems, the lithological, structural-geomorphological and neotectonic conditions of the territory were studied. Field observations and publications based on geological survey data were the factual material for the studies.Results. Various types of uplifts and troughs, geodynamically active zones and lineaments were identified. The formation of structures is associated with deep (intracortical) stresses of compression and tension, under the influence of which the tectonic-gravity and suffosion-karst processes negative for the territory of the nuclear power plant are activated. Among the ancient Precambrian faults of the crystalline basement, the latitudinal Sudzhen-Ikorets and submeridional Semiluki-Lipetsky faults are active. The latter is considered as a geodynamically active zone. At the NPP site and in its vicinity, the zones of increased fracturing and permeability were identified, which is consistent with the buried forms of the relief — paleo-reliefs of the Don river and its tributaries. These zones are found to be deeply embedded in the Cretaceous and Devonian carbonate rocks, which is the reason for the increased leaching of these rocks and the removal of fine particles from the fluvioglacial strata. A quantitative assessment of summary and step-by-step amplitudes and speeds of neotectonic movements was carried out.Conclusion. The territory of the Novovoronezh NPP is geodynamically calm, the movement speeds (both calculated and according to instrumental measurements) are relatively low; however, these movements activate exogenous processes, which in turn negatively affect the stability of the Novovoronezh NPP site.

Deep structure of South Caspian depression and connection of seismic-geological conditions with oil-gas bearing content

The geological model of South Caspian depression is specified, the seismic-geologic and geodynamic conditions of deep layers studied, a basis for the exploration of oil-gas structures in a new aspect developed as well. A complex analysis of geological, geophysical and seismological data obtained recently has been conducted, the distribution of the depth of sedimentary, granite and basalt layers, as well as the maps of the borders dividing them – Mokhorovich (Mokho-M), Konrad (K) and base surface (F) developed. It was defined that the depth of M surface fluctuates within 40–55 km, K – 20–35 km and the base surface 5–25 km. The history of the geological development of South Caspian depression has been studied, magmatic processes (intrusion formation), seismic-geodynamic activity (earthquakes), geotectonic movements (horizontal, vertical and circle), as well as the oil-gas perspectives of the deep layers of the region estimated. It is shown that the thickness of the granite layer in South Caspian depression decreased from 5–25 km to 4–5 km, and disappears in the deepest (1025 km) part of the Caspian Sea. Corresponding changes in the seismic activity on the map of earthquake epicenter and the distribution of epicenters by the depth were observed in the circle scheme within the intervals mentioned above, and the violent earthquakes with М≥6–8 coincide with 7–20 km diapason.

Lithospheric Thermal Structure in Jinggangshan City: Implications for High Geothermal Background

Jinggangshan City, which is located in the southwestern part of Jiangxi Province, is rich in hot springs. However, lack of geothermal studies has limited the exploration and utilization of the geothermal resources in this city. This study estimated the terrestrial heat flow in Jinggangshan City through well logging and analyses of rock thermal conductivity and heat production. Based on this and the surrounding geoscience transect and the Crust 1.0 model, this study constructed a one-dimensional lithospheric thermal structure by solving the steady-state heat conduction equation. Furthermore, the deep temperature distribution in Jinggangshan City was obtained to better understand the geodynamic condition of the geothermal resources in this city. The results show that the heat flow in this city is around 83.52 mW/m2, indicating the high heat background for the formation of geothermal resources. According to the lithospheric thermal structure of Jinggangshan City, the mantle contributes more to the terrestrial heat flow (qm/qc > 1) than the crust. The temperature of the Mohorovicic discontinuity (the Moho) is 671.7°C, which is consistent with that below the Tanlu deep fault (620–690°C). Moreover, the calculated depth of the Curie surface (585°C) is 27 km, which is consistent with the Curie isotherm depth estimated from aeromagnetic data. This consistency verifies the validity of the lithospheric thermal structure of Jinggangshan City constructed in this study. In summary, the high heat background plays an important role in the formation of geothermal resources in Jinggangshan City.

THROUGHGOING FLUID-CONDUCTING STRUCTURES: CONCEPTUALIZATION, TERMINOLOGY, TYPES, PROPERTIES, AND THE ROLE IN FLUID CIRCULATION

In this paper the review and analysis of global data on throughgoing fluid-conducting structures is performed, the problematic issues of related concepts and terminology are considered, typification of structures by various criteria is proposed and their role in fluid circulation and in lithogenesis and evolution of sedimentary basins is accessed. Such structures are ubiquitous and are an integral part of the drainage system of the upper crust, although the intensity of their distribution and impact on fluid circulation vary widely and increase drastically in certain geological and geodynamic conditions. At the local and subregional scales, throughgoing structures and related phenomena show uneven, clustered distribution. The key role of throughgoing structures in fluid circulation, including the migration of hydrocarbons and pollutants, is determined by their intersecting and throughgoing nature with respect to layered inhomogeneities, including sealing (low permeability) horizons, and by usually much higher permeability than that of the host rocks. The vertical nature of structures and localized vertical fluid flow across lateral lithological and hydrodynamic boundaries cause the formation of thermal and geochemical anomalies and disequilibrium of the water-rock system, accompanied by the interaction of conduit fluids with host rocks and reservoirs and by alteration of the rocks that contain them. This determines the leading role of throuhgoing structures in superimposed lithogenesis and ore mineralization. The fluid conductivity of throughgoing structures is variable over time because it depends on their origin, stages of their formation and secondary changes. In this regard, the comparison of this ability between morphogenetic varieties of throughgoing structures is generally difficult, although the most effective in this respect are structures of karstic origin. For structures of fluidodynamic type, the greatest permeability and intensity of fluid flows through the conduits are characteristic of the periods of their formation and immediately after them, as well as of the periods of activation, which are usually associated with tectonic events.

Происхождение магм и вулканических взрывов в океанических и субдукционных областях с учетом данных о горячей гетерогенной аккреции Земли

The obtained numerous proofs of hot heterogeneous accretion of the Earth and the calculated quantitative models of magmas lead to a fundamentally new solution for the genetic problems of magmatic petrology. They indicate the formation of geospheres and the initial substance of magmas resulted from fractionation of the global magmatic ocean, which arose as a result of a huge impact heat release during mantle accretion. Due to the increase in temperature as accretion progressed, a reverse geothermal gradient first existed in the mantle, and on the early Earth there were no modern geodynamic conditions. The gradual warming of the mantle by the initially very hot core led to the formation of a direct geothermal gradient and convection as well as oceanic and subduction regions in the Neoproterozoic. In the oceans, magmas are formed as a result of decompression melting during the surfacing of eclogite lenses, which emerged by way of filling impact craters with melts of the synaccretionary magmatic ocean. Magmas of subduction regions are the result of frictional melting of the magmatic ocean differentiates. Volcanic explosions occur under the influence of high pressure of the gas phase preserved by decompressional solidification of magmas at the shallow stage of ascent.

Geological setting and genesis of the Kurmansky gabbro-trondhjemite massif (Middle Urals)

This paper reports the results of petrogeochemical studies of the Kurmansky gabbro-trondhjemite massif (eastern slope of the Middle Urals), lying in the western part of the large Reftinsky allochthonous block within the accretion East Uralian megazone. The relevance of this study is determined by the uncertainty in geodynamic setting and formation conditions of the rock massif and its role in the evolution of the Ural Mobile belt. We specified the countours of the massif. It is shown that the rocks were resulted from spatiotemporal convergence of partial melting in the mantle and lower crust at the island-arc stage of the Ural Mobile belt evolution. Partial melting of mantle peridotite, under the influence of an aqueous fluid rising from the subduction zone, initiated the occurrence of basite melts. The separation of the melt and its subsequent evolution to the compositions of gabbrodiorite and diorite took place at Ptot=10 kbar. Trondhjemites were formed as a result of partial melting of amphibolites at Ptot≥8 kbar, PH2O=0.1–0.2 kbars. The crystallization of trondhjemites in the crust was accompanied by the wollastonite skarns on contact with carbonate rock and xenoliths culminated at mesoabyssal level, Ptot=PH2O=1 kbar. The comparison between the composition of Kurmansky gabbro-trondhjemite massif and the island-arc- and collision-related magmatic suites in the region allowed us to assume that the Kurmansky massif belongs to the independent Early Devonian (?) gabbro-trondhjemite complex of island arc origin. The rock metamorphism conditions were evaluated, with the transformations supposedly related to the accretion of early island arc complexes at the Murzinsky-Aduysky microcontinent, which took place in the Devonian.

Geochemical features of the devonian plutonic rocks of the Reftinsky massif (Middle Urals)

This article examines the Devonian plutonic rocks of two massifs – Khomutinsky and Yuzhno-Khomutinsky, which are located in the western part of the Reftinsky massif. The rocks of the Khomutinsky and Yuzhno-Khomutinsky massifs are divided into gabbroid and granitoid associations. Their chemical composition, the content of pertrogenic, rare and trace elements were studied. Based on the data obtained, the rocks were assigned to the calc-alkaline series, according to the ratio of sodium and potassium, they are rocks with a sodium type of alkalinity. The peculiarity of the studied formations lies in the differences in the nature of alkalinity, thus the rocks of the gabbroid association in terms of the K2 O content are transitional from low to moderate potassium varieties, and the rocks of the granitoid association are characterized by a sufficiently high potassium content and correspond to the high potassium calc-alkaline series. Comparative analysis with basalts and granites of island arcs allows us to conclude that the Khomutinsky and YuzhnoKhomutinsky massifs were formed in an island arc geodynamic setting. Relevance. The geochemical features of the rocks of the Devonian intrusions in the Eastern zone of the Middle Urals have been studied very poorly to date, which makes it difficult to restore the geodynamic conditions of their formation and compare the processes of magmatism in the East of the Middle Urals with other regions of the mobile belt. The data presented in the work will make it possible to fill the existing gap to some extent and thereby help to clarify the patterns of magmatism evolution and the history of the formation of the Urals. The purpose of the work. Study of the contents of petrogenic, rare and trace elements of the Khomutinsky and Yuzhno-Khomutinsky massifs. Comparison of the geochemical features of the rocks of these intrusions with similar formations formed in island-arc geodynamic conditions. Research methodology. The chemical composition of rocks was studied by the X-ray fluorescence method, which was performed on a multichannel spectrometer SRM-35 with the determination of losses on ignition by the gravimetric method and the determination of the content of ferrous iron by the titrimetric method. Analysis of the content of rare and trace elements in rocks was carried out on inductively coupled plasma mass spectrometers ELAN 9000 and NexION 300S. Analytical data are presented in the form of discrimination diagrams. Results. The rocks of the Khomutinsky and Yuzhno-Khomutinsky massifs are divided into gabbroid and granitoid associations. Based on the obtained geochemical data, the rocks were assigned to the calc-alkaline series. According to the ratio of sodium and potassium, they are rocks with a sodium type of alkalinity. It is shown that the rocks of the gabbroid and granitoid associations differ in the character of alkalinity. The former in terms of K2O content are transitional from low to moderate potassium varieties, the latter are characterized by a fairly high content of potassium and correspond to the high potassium calc-alkaline series. Conclusion. Comparison of the studied rocks in terms of geochemical features with basalts and granites of island arcs allows us to conclude that the Khomutinsky and Yuzhno-Khomutinsky massifs were formed in an island-arc geodynamic setting.

Analysis of geodynamic conditions and zoning of oil and gas fields distribution based on the geological-geophysical data (in the context of Yevlakh-Aghjabedi territory)

The paper briefly characterizes the geodynamic conditions of before Hercinian, Hercinian and Alpine periods of regions evolution playing major role in formation of Meso-Cenozoic fold structures in the territory of Yevlakh-Aghjabedi oil-gas bearing region. During the analysis of structural-tectonic features highlighted in 3D models and geological-geophysical deep sections through the regional profiles of various directions, geodynamic conditions are observed (predicted) in the studied region, which cover the following stratigraphic intervals: - Permian-Triassic (basis) - Jurassic-Cretaceous and Paleogen - Maikop-Miocene and - Pliocene-Quaternary. The authors suppose that the favorable geodynamic conditions in these intervals contributed to the zoning of oil and gas deposits distribution.

Deep degasion and oil-and-gas containment of the Eastern (Ukrainian) Carpathians: geodynamic and geothermal aspects

The article presents the results of comprehensive analysis of geodynamic conditions, geothermal regime, distribution of oil-and-gas deposits, as well as degassing of Earth’s crust in the Ukrainian sector of the Eastern Carpathians, being a part of the Carpathian petroliferous province. Within the boundaries of the Ukrainian sector of the Carpathians, three main tectonic units are distinguished: the Pre-Carpathian Foredeep, the Folded Carpathians, and the Transcarpathian Trough. Each of them consists of several zones or tectonic covers. Oil-and-gas deposits are mainly concentrated within the Pre-Carpathian Foredeep. Gas deposits prevail in its outer zone, while the oil deposits in inner one. Seve-ral small methane deposits were discovered in the Transcarpathian Trough, and only one deposit in the Folded Carpathians.Earth’s crust within the whole Carpathian region is characterized by high level of gas saturation. Here methane and carbon dioxide prevail. According to chemical composition of gas and isotopic signature of carbon in carbonaceous gases, two areas can be distinguished within the region: north-east, where methane dominates, and south-west, where carbon dioxide prevails. These areas are divided by the Central Carpathian tectonic zone. They adhere to geothermal zoning. The former is characterized by low geothermal activity (heat flow density is 35—60 mW/m2), and the latter — by high level activity (heat flow density exceeds 70 mW/m2).
 Hydrocarbon deposits are formed in three stages, concurring with three stages of tectonic evolution of the Carpathians. The first stage is distinguished by accumulation of primary components (carbon, hydrogen, oxygen) and thermal activity increase. It concurs with a stage of lithosphere destruction and extension, ocean basin generation, sedimentation, asthenosphere uplift, as well as formation of deep fluid-and-gas flows. At the second stage, hydrocarbon generation commences. It corresponds to the stage of lithosphere collapse, activation of subduction and collision processes, depression and heating of sedimentary strata, enriched in organic substances and water. At the third stage, the processes of hydrocarbon generation, migration and accumulation proceed. Time interval for deposit formation is coincident with the last stage of the Carpathians evolution during Badenian and Sarmatian time, as well as with formation of overthrusts, deep depressions, and thick masses of Miocene argillaceous deposits.

Physicochemical and geodynamic conditions for the formation of the Sarsanginsky complex of the border zone of the Southern and Middle Urals

The article describes the geological structure of the Sarsanginsky gabbro-diorite-plagiogranite complex located in the border zone of the Middle and South Urals. The formation of its massifs took place in the late Silurian time in the abyssal zone at depths of about 6,5–7,0 km. The temperature range of crystallization of granodiorites was 900–990 С, and for gabbro 1180–1280 С. The system pressure at this moment corresponded to 190–200 MPa. The gabbro that make up the massifs under consideration were formed under stretching conditions on the oceanic crust. In terms of petrogeochemical features, they correspond to rocks at the base of island arcs and belong to the ophiolite formation.

Modern geomechanical assessment of influence of rockbursts in tectonic areas on mine stability in the North Urals Bauxite Mine

Experience of the North Urals Bauxite Mine shows that the current conditions, namely, mining technologies and rates per extraction panels, as well some other geotechnical factors not always and not in full conform with the actual geology and geomechanics, which affects mining safety. VNIMI accomplished the research aimed at efficiency evaluation of room-and-pillar mining in complicated geodynamic conditions of the North Urals Bauxite Mine. It is found that stability of mine support elements is greatly affected by additional dynamic load induced by deformation of block rock mass. Mining-initiated reactivation of healed faults leads to liberation of large amounts of accumulated energy, which results in dynamic failures in mines. The quantitative estimation of such energy was carried out using Russian software PRESS 3D URAL. The computer modeling results point at the additional concentration of dynamic stresses during slippage along the healed faults, which should be taken into account in mine support design. Before and during actual stoping in extraction panels, it is required to implement geodynamic zoning to update the local tectonic structure, as well as the anticipatory computer-aided prediction (using the adapted anticipatory computerized simulation in PRESS 3D URAL) of the stress–strain behavior and geodynamic safety of rock mass with regard to the widely varying geological factors, their complication with growing depth, as well as aggravation of geodynamic regime and rockburst hazard.

Integral assessment of the geodynamic conditions for the formation of the Black Sea basin and connection with the current regime of groundwater in its northwestern shelf

The paper has a multidisciplinary character connecting bathymetric, geophysical and geological information to innovatively reconstruct the geodynamic conditions of the Black Sea basin formation, their influence on the modern relief and groundwater regime within its northwestern shelf as a reference region. The major goal is the rationale of modern geodynamic settings for the Black Sea Basin against the back- ground of the processes of its closure under tangential compression conditions, as well as their relation- ship with the hydrogeological conditions of the shelf zone. As primary evidence, the author determined the spatial positions of the Constanta-Sinop and SubPontian Suture Zones, pinpointing absorption locations of the Earth's crust at subduction zones. The facts and arguments presented in this paper are well integrated into the scheme of the oncoming of the Pontides island arc to the Eurasian Plate and the gradual closure of the back-arc marginal Black Sea Basin with a crust of transitional-type crust. The specific feature of the study is an innovative approach to comprehensive analysis of data that are a result of geological and geophysical works within the Black Sea water area. In doing so, major attention is paid to the spatial morphostructural analysis and interpretation of newly integrated digital data array, as a result of bathymetric surveys, namely the EMODnet 2019—2022. The subject of analysis is the basic structural surfaces, including the Modern and on its margin consolidated basement. New justification is formulated on the confinement of gas seeps and mud volcanoes, within the Black Sea Basin, to the deep earth`s crust structures. The graphical correlation of the mentioned ones is performed as well as their spatial position in the structural-geodynamic model of the region is theoretically substantiated. A generalized geomorphological zoning of the northwestern shelf of the Black Sea with the identification of the Dobrogea, Odesa and Kalamit zone is proposed. Within the Odesa geomorphological region, an integrated geological and geomorphological analysis was carried out and, as a result, dividing the shelf into submarine groundwater discharge (SGD) zone of aquifer was substantiated. The study, carried out by the author is of crucial importance to understanding the tectonic and geo- dynamic characteristics of the Black Sea Basin as well as for forecasting SGD zones and fresh groundwater resources. It is recommended to set targeted prospecting works to assess fresh groundwater resources in order to meet the water needs of coastal communities.

PETROLOGY OF CENOZOIC DYKES ON THE ARGENTINE ISLANDS (WILHELM ARCHIPELAGO, WEST ANTARCTICA)

Dyke swarms that intrude Paleogene granitoids of the Argentine Islands near the Ukrainian Antarctic Station "Akademik Vernadsky" were studied. The field relations and mineralogical, petrographical and geochemical properties of the dykes allow their relative geological age and the geodynamic conditions to be clarified. The magmatic activity in the study area did not cease, at least until the end of the Miocene when the processes of orogenic uplift led to the erosive exposure of the Paleogene granitoids of the Barchans-Forge Massif. Tectonic exhumation of the latter was accompanied by the intrusion of dykes of different compositions at different depths. Cenozoic basalt and diabase dykes are the most common. Most are subvolcanic fractured intrusions formed after the complete exhumation of the host granitoids, which ended by the Miocene (11 Ma). The basaltic dykes are probably one of the youngest representatives of magmatism in the region. They have an intermediate position between high-LILE tholeiites and the calc-alkaline series. However, the nature of contamination of the basaltic dykes by crustal rocks requires additional research. Cenozoic microdiorites dykes are rarer than basaltic ones. They are hypabyssal fractured intrusions formed during the tectonic exhumation of the Barchans-Forge granitoids between the beginning of the Paleocene and the end of the Miocene (61-11 Ma). The microdiorites belong to the orogenic calc-alkaline series and they could be related to subduction processes. The discovery of only one dacite dyke indicates the rarity of acid magmatism during the Cenozoic period. It occurs as a fractured intrusion and formed after the exhumation of the host granitoids. The dacite dyke belongs to the calc-alkaline series, which, along with other compositional properties, suggests that dacite and microdiorite dykes are comagmatic.