Geodynamic Conditions Research Articles

PALEOZOIC INTRAPLATE MAGMATISM OF THE EAST EUROPEAN PLATFORM: COMPARATIVE ANALYSIS OF THE PRIPYAT-DNIEPER-DONETS RIFT ZONE AND THE KOLA-ARKHANGELSK PROVINCE

This paper presents a comparative analysis of geochronological, geochemical, Sr-Nd isotopic data and geodynamic conditions for the Devonian magmatism of the East European Platform, using as an example the Pripyat-Dnieper-Donets rift zone in the south of the platform and the Kola alkaline province in the north.The Late Paleozoic rifting in the south of the platform was accompanied by magmatism, which formed a wide range of rocks, from alkaline-ultramafic lamprophyres and orangeites, non-diamondiferous kimberlites and carbonatites to typical tholeiites, trachyandesites, and trachyrhyodacites. Activation of rifting processes in the north of the platform has also produced a compositional diversity of magmatic occurrences dominated by kimberlites, in particular diamondiferous (Arkhangelsk diamond-bearing province), which is the main distinctive feature of the place. The Pripyat-Dnieper-Donets rift zone is subject to reverse lateral geochemical zonality of the mantle sources – from those depleted in the axial zone of the Dnieper-Donets trough to more enriched in the marginal parts – trough shoulders (Azov region, Voronezh crystalline massif): along the southeast to northwest axis of the rift zone to the Zhlobin saddle (orangeites, alkaline picrites of the Zhlobin alkaline-ultramafic complex) and in the Pripyat trough (Pripyat alkaline and subalkaline mafic complex) as well was perpendicular to the axis from the central part of the Dnieper-Donets trough to the southwest towards the Eastern Azov region (non-diamondiferous kimberlites) and to the northeast towards the Voronezh crystalline massif.Currently available petrological-mineralogical and isotopic-geochemical data on magmatites of both large magmatic structures suggest significant lithospheric heterogeneity, different types of sources of formation of rocks, and a significant influence exerted by the crustal component both in the southern and northern parts of the East European platform.

AGE AND GEODYNAMIC SETTINGS FOR FORMATION OF CARBONATITE COMPLEXES AND ASSOCIATED RARE METAL DEPOSITS OF THE SOUTH URAL

The Ilmen-Vishnevogorsky and Buldym carbonatite complexes occurring in the Southern Urals represent linear deformed carbonatite complexes. Their origin, as well as the age and geodynamic conditions remain the subject of debate. The isochron methods (Rb-Sr, Sm-Nd, TIMS) and local U-Pb-dating of zircons (SHRIMP II and LA-ICP MS) of these carbonatite complexes were employed to determine the age and duration of the stages of alkali-carbonatite magmatism and associated rare-metal ore formation. The Silurian-Devonian U-Pb zircon ages of the early phases of Ilmen-Vishnevogorsky miaskites and carbonatites were determined as 420.7±11 Ma (S2) and 417±2.8 Ma (D1), respectively. In the later phases of miaskites and carbonatites, early zircons are resorbed, they have broken isotope systems, and later zircon generations form a cluster of 386±7.6 Ma (D2). The Lower Permian U-Pb age of zircon 280±8 Ma (P1) was determined in the miaskite-pegmatite and late carbonatite. The isochron dating of late ore-bearing varieties of carbonatites provided the ages from the Lower Permian to the Early Triassic (P1–T1): 254±18 Ma, Sm-Nd and 247±4 Ma, Rb-Sr, IVC; 280±53 Ma, Sm-Nd, Buldym complex. Thus, the generation and intrusion of alkaline magmas in the Urals occurred ~420 Ma (S2–D1), synchronously with the formation of island-arc complexes. They are related to rifting on the emerging continental margins. The tectonic activity and formation of alkaline rocks and carbonatites proceeded in the Middle Devonian (~380 Ma, D2); it correlates with the accretion-collision stage of the Urals development. At the stage of "hard" collision (~280 Ma, P1), the Ilmen-Vishnevogorsky and Buldym complexes were plastically deformed, underwent melting and emplaced conformably with collision-slip tectonic structures. Recrystallization of rocks and minerals, plastic and brittle deformations, processes of pegmatitic, carbonatitic and rare-metal ore formation are associated with palingenic-metasomatic transformation of rifting alkaline complexes of Silurian-Devonian age at the collision and post-collision (~250 Ma, P3–T1) stages of the Urals emplacement.

Volcanites of neoproterozoic ophiolites Kalgyn massif (Northeast Asia): new geochemical and isotopic data

The Kalgan ophiolite massif is a unit of the ophiolite association of the Chersky collision belt. It is part of the Verkhoyano-Kolyma folded system on Northeast Asia. The Kalgan massif includes a complex of mantle peridotites, a lower-crust complex represented by ultrabasic cumulates, cumulative gabbro-amphibolites and amphibolites, and an upper-crust complex represented by metabasalts. New geochemical data obtained by the ICP-MS method, as well as data on the isotopic composition (Sm, Nd), made it possible to significantly clarify the geodynamic conditions for the formation of volcanites and to determine the features of the sources of parent melts.

New bulk rock and age data on the changes in magma evolution during the Miocene, Galatean volcanic area, central Anatolia, Turkey: A review

The Galatean Volcanic Province (GVP) lies within the Sakarya tectonic belt in the northwest of central Anatolia, Turkey, south of the North Anatolian Fault, cropping out over 12,000 km2. It consists of Early Miocene intermediate to acid lavas, pyroclastic rocks, volcaniclastic deposits, and Late Miocene OIB-like basalts. Our study is based on new bulk geochemistry, SrNd isotopes, and 40Ar/39Ar dating of the volcanic rocks from the south-western part of GVP, but integrates all the available previous data to understand how magmas evolved in the post-collisional geodynamic condition in the GVP. The initial eruptions were rhyolitic, as domes or pyroclastic deposits (Group 1) and basaltic lavas (Group 2) during the Early Miocene. Group 2 is also represented by large volumes of basaltic-andesitic, trachyandesite-dacite/trachydacite lava flows, small intrusions, and pyroclastic deposits as generated between 21 and 14 Ma. Relatively low 87Sr/86Sr ratios (0.705–0.706) of the early rhyolites (Group 1), similar to all the rocks from Group (2), suggest the generation of hybrid melts with variable contributions of mantle-derived and crustal material. The volcanic activity ends with OIB-like basalts (11–7 Ma) showing the lowest 87Sr/86Sr (∼0.703) suggesting an asthenospheric origin.The geodynamic model, based on post-Cyprian slab rollback, results in long-term (22–13 Ma) post-collisional delamination/drip processes that support magmatism. This magmatism is generated in the lithospheric mantle, with the formation of basaltic melts and acid hybrid melts showing variable contributions of mantle-derived and crustal materials in a complex trans-crustal magma plumbing system. Complex mixing of various intra-crustal magmas and fractional crystallization processes generated a huge volume of volcanic rocks. The Late Miocene small-volume OIB basalts were asthenospheric melts that during the late stage recorded localized decompression melting processes.

UPPER CRETACEOUS–LOWER EOCENE MUDSTONES OF THE OUTER CARPATHIANS (PETROCHEMICAL AND PALEOGEODYNAMIC ASPECTS)

The mineral types of the Upper Cretaceous–Lower Eocene greenish-gray mudstones of the Skyba and Boryslav-Pokuttya nappes of the Outer Carpathians were studied. According to sedimentological features, these mudstones belong to hemipelagites and contain information about the background sedimentation conditions of the deep-sea oceanic basin. The purpose of the work is to clarify the paleogeodynamic features of the basin based on the results of studying the material composition of the Upper Cretaceous–Lower Eocene background mudstones, which in particular are part of the variegated-colored horizons. Research methods were geological mapping, X-ray structural, sedimentological, lithostratigraphic, petrogeochemical, geodynamic analysis. On the classification module diagram (Na2O+K2O)/Al2O3–(FeO*+MnO+MgO)/SiO2, the figurative points of the contents of the Upper Cretaceous–Lower Eocene mudstones of the Stryi, Yamna, and Manyava suites fall into the fields corresponding to two mineral types: a mixture with a predominance of montmorillonite and three-component mixture of chlorite+montmorillonite+hydromica composition. According to the obtained data, a gradual change in the conditions of the sedimentary environment from the Late Cretaceous to the Eocene can be traced, with a successive increase in the normalized alkalinity modulus and a decrease in the phemic modulus. On the paleogeodynamic discriminant diagrams (FeO*+MgO)–TiO2 and F1–F2, figurative points of Upper Cretaceous–Lower Eocene mudstones form petrochemical distribution trends that cover the fields of geodynamic conditions from passive to active margins of the sedimentation basin. The Cretaceous–Paleogene pelagic mudstones of the Sicilian domain of the Alpine Belt have a similar distribution of petrochemical components. The mineral assemblages found in the mudstones of the Skyba and Boryslav-Pokuttya nappes are typical for deep-sea clay sediments of modern oceans. The presence of montmorillonite and chlorite in the background argillites indicates a high probability of a contribution to the background petrofund of the sedimentatary basin by a femic magmatic component of endogenous origin, realized as a manifestation of volcanic and hydrothermal activity, synchronous to sedimentogenesis. An exogenous source could be the magmatic material transferred or changed by the processes of halmyrolysis, which is not synchronous with sedimentation. The Late Cretaceous–Early Eocene geodynamic events of the Outer Carpathian sedimentary basin developed in front of the ALCAPA and Tisza-Dacia terranes of the Alpine Tethys. Convergence, which caused the formation of the accretionary prism in front of the terranes, could contribute to the riftogenic (?) opening, deepening of the Outer Carpathian Basin, where the penetration of synsedimentary endogenous material, mainly of the basic composition, took place. This material could be the rock-forming source of the basin substrate, on which the mineral assemblages of the background hemipelagic mudstones were formed.

Comprehensive research of the distribution of tellurium-bismuth mineralization in the ores of the Abyz and Maleevskoe sulfide deposits (Republic of Kazakhstan)

Abstract. Within the formations of ensimatic and ensialic island arcs in the territory of Central and Northern Kazakhstan, there are more than thirty pyrite deposits enriched in copper, lead, zinc, gold, silver and rare metal mineralization, which is still insufficiently studied. Relevance. The need to replenish information on tellurium-bismuth mineralization in ores of sulfide deposits formed in ensimatic (Abyz deposit) and ensialic (Maleevskoe deposit) island-arc systems, to establish a spatial connection of this type of mineralization with geodynamic conditions and predict the potential for their associated extraction from ore. Aim. To study and compare morphological characteristics, distribution patterns and conditions for the formation of tellurium-bismuth mineralization in ores of pyrite deposits formed in different island-arc geodynamic settings. Methods. Inductively coupled plasma mass spectrometry, mineragraphic and mineralogical analyses, scanning electron microscopy in combination with X-ray spectral microanalysis, Raman spectroscopy, thermobarogeochemical studies. Results. A comparison of the pyrite deposits of the Rudno-Altai and Chingiz-Tarbagatai island arc systems showed many similarities and differences between them. The deposits have a multi-stage formation and a similar mechanism of ore deposition with similar physicochemical conditions for the formation of tellurium-bismuth mineralization. A spatial relationship between Te-Bi mineralization and geodynamic settings was established: for deposits associated with paleooceanic structures, a predominance of the tellurium element is observed, and for continental rifts, a predominance of the bismuth element.

Geodynamic controls on clastic-dominated base metal deposits

Abstract. To meet the growing global demand for metal resources, new ore deposit discoveries are required. However, finding new high-grade deposits, particularly those not exposed at the Earth's surface, is very challenging. Therefore, understanding the geodynamic controls on the mineralizing processes can help identify new areas for exploration. Here we focus on clastic-dominated Zn–Pb deposits, the largest global resource of zinc and lead, which formed in sedimentary basins of extensional systems. Using numerical modelling of lithospheric extension coupled with surface erosion and sedimentation, we determine the geodynamic conditions required to generate the rare spatiotemporal window where potential metal source rocks, transport pathways, and host sequences are present. We show that the largest potential metal endowment can be expected in narrow asymmetric rifts, where the mineralization window spans about 1–3 Myr in the upper ∼ 4 km of the sedimentary infill close to shore. The narrow asymmetric rift type is characterized by rift migration, a process that successively generates hyper-extended crust through sequential faulting, resulting in one wide and one narrow conjugate margin. Rift migration also leads to (1) a sufficient life span of the migration-side border fault to accommodate a thick submarine package of sediments, including coarse (permeable) continental sediments that can act as source rock; (2) rising asthenosphere beneath the thinned lithosphere and crust, resulting in elevated temperatures in these overlying sediments that are favourable for leaching metals from the source rock; (3) the deposition of organic-rich sediments that form the host rock at shallower burial depths and lower temperatures; and (4) the generation of smaller faults that cut the major basin created by the border fault and provide additional pathways for focused fluid flow from source to host rock. Wide rifts with rift migration can have similarly favourable configurations, but these occur less frequently and less potential source rock is produced, thereby limiting potential metal endowment. In simulations of narrow symmetric rifts, the conditions to form ore deposits are rarely fulfilled. Based on these insights, exploration programmes should prioritize the narrow margins formed in asymmetric rift systems, in particular regions within several tens of kilometres from the paleo-shoreline, where we predict the highest-value deposits to have formed.

Unraveling the tectonic evolution of the Andean hinterland (Argentina and Chile, 30°S) using multi-sample thermal history models

The Andean hinterland of Chile and Argentina defines a region of voluminous magmatism, polyphase deformation, and high topography above a long-lived subduction zone. Construction of this high-elevation domain has been variably attributed to isostatic uplift during crustal thickening induced by internal hinterland shortening, underthrusting during growth of the external thrust belt, or lower crustal flow. Alternatively, uplift may be related to dynamic processes associated with lithospheric foundering or flat-slab subduction. This study integrates geo/thermochronological, structural, magmatic, and sedimentological datasets to reconstruct hinterland evolution and evaluate potential drivers of exhumation. Our thermal history modeling approach implements a new time-depth extension to HeFTy 2 software, which enables simultaneous inversion of multiple samples along a structural or topographic profile. This extension addresses transient effects such as isotherm deflection and the transition from geothermal to atmospheric gradients and permits changes in the relative position among samples (folding, tilting) within user-defined constraints. Single- and multi-sample modeling results based on published apatite (U-Th)/He and fission track data (AHe, AFT) along the western Andean hinterland confirm late Eocene (∼30–40 Ma) cooling below at least ∼120°C, whereas thermal histories derived from new AHe, AFT, and zircon He analyses from the eastern hinterland resolve Mesozoic cooling below ∼80–160°C, followed by protracted residence at ∼60–80°C and rapid exhumational cooling in the early Miocene. Multi-sample models further require ∼10° eastward tilting of eastern sample locations, compatible with hinterland uplift via underthrusting and development of a crustal-scale fault-bend fold that was geometrically and kinematically linked to shortening in the external (eastern) thrust belt. Results underscore the enhanced resolution of multi-sample thermal history models in testing structural hypotheses and deciphering the timing, magnitude, and mechanisms of exhumational cooling during changing geodynamic conditions.

Седиментаційні індикатори сучасних морфодинамічних процесів на скелях масиву «Камінь» (с. Урич, Східні Бескиди, Українські Карпати)

The paper studies the types of modern morphodynamic processes on the sandstone tor “Kamin`” (“Stone”) in the village Urych (Eastern Beskydy, Ukrainian Carpathians) as a nature monument and historical and cultural reserve. It reveals interrelationships between the modern manifestations of the processes and the sedimentological facies of the Paleogene rocks of the Yamna Formation. During the formation of the Carpathian trust fault structure, they were created in the geodynamic conditions of the Outer Carpathian deep-water oceanic paleobasin and deformed during the stages of accretion and orogeny. The main research methods were morphological, morphodynamic, sedimentological, and lithological. Modern morphodynamic processes on the tor walls are classified by their origin, localization within the studied object, and the amount of tor wall coverage. Morphodynamic processes can be classified into different types such as soaking and very small pits; destruction; flaking; spalling; dimples weathering; alveolar weathering; corrasion and washing away the grains; linear underground erosion; biogenic superficial weathering; biogenic linear weathering; block collapses; joint-guided weathering: along tectonic, tensile, weathering, lithological cracks; gravity cascade folds. According to the amount of coverage of the tor walls, the following are distinguished: microprocesses (local manifestations), medium-scale and large-scale processes, with a destruction depth of 1-10 сm. Medium-scale processes that occur on tor superficials are related to primary sedimentary structural-textural features of rocks and their lithological composition. Fractured paragenesis of the Sub-Carpathian and Anti-Carpathian directions dominate large-scale processes. Studies of the tor destruction processes are important to determine the preservation methods of the sandstone tor “Kamin`” as a valuable object of historical, cultural, and geotourism heritage. The obtained results indicate that individual tor blocks are strongly affected by superficial processes, on which deep polygenetic cracks are superimposed. This provides a basis to implement measures for strengthening the stability of the tor.

Современное представление о промышленной классификации колчеданно-полиметаллических месторождений Рудного Алтая

There are many classifications of polymetallic deposits. Many researchers, based on the genetic relationship of the deposits, attribute the deposits of the Rudny Altai to the VMS Kuroko type. Other authors classify polymetallic deposits of the Rudny Altai, relying on geodynamic conditions and modes of their formation. Such a variety of classifications makes it difficult to understand and use these classifications for various kinds of research, and questions also arise when comparing with foreign analogues. Therefore, the authors of this article propose to consider the modern unified classification of deposits of the Ore Altai according to J.W. Lydon (1988), based on the division of polymetallic deposits of VMS by volume ratio Zn/(Zn+Pb) into 2 main industrial genetic types (Zn-Pb-Cu and Cu-Zn). The first type (Zn-Pb-Cu) has a mass ratio of Zn/(Zn+Pb) from 0.70 to 0.80; the second type (Cu-Zn) is more than 0.95. Practically all deposits of the Ore Altai can be attributed to the Zn Pb-Cu group, as having mass ratios of Zn/(Zn+Pb) from 0.64 to 0.86 and localized in medium to acidic calcareous-alkaline volcanic rocks mainly of Phanerozoic age

Alkaline–Salicic Kurung Complex of the Ket-Kap–Yuna Igneous Province (Aldan Shield, Russia): Petrogenesis and Geodynamic Conditions of Formation

Abstract —Integrated geological data, petrogeochemical characteristics of magmatites of the Kurung complex (the Ket-Kap–Yuna igneous province of the Aldan Shield), and previously published isotopic data along with the results of geochronology and geochemistry research provide evidence for this complex evolving in the Late Cretaceous in a setting of riftogenesis (final phase) of continental margins. Similar to the Late Jurassic–Early Cretaceous polyformational volcano-plutonism of the Aldan Shield, the Late Cretaceous alkaline magmatism in the Ket-Kap–Yuna province is associated with the tectonomagmatic activation which manifested itself mainly as continental margin rifting associated with deep reorganization of the southwestern, southern and southeastern framing of the Siberian craton triggered by gravitational sliding of the lithospheric plates. Results of the petrogeochemical analysis of the studied magmatites revealed that the heterogeneous rock groups identified within this rock complex are not related to each other by fractional or other type of differentiation, thus suggesting their possible derivation as a result of fluid syntexis-type interaction between mantle-derived alkali–basite melt and felsic crustal melts. Alkali–basite parent melts are shown to have formed during partial melting of variably enriched mantle which is widely spread beneath the Aldan Shield and is varied in composition (from BSE enriched to nearly EM-I). Origination of such deep-seated melts (magma sources) was associated with the rifting processes (strike-slip tectonics) triggered by the setting of gravitational sliding of lithospheric plates. The formation of alkaline–salic magmas of the Kurung complex is associated with large-scale selective assimilation of crustal material by high-temperature fluidized mantle magmas during their ascent to the surface, possibly as a result of fluid syntexis of alkaline–basite mantle magmas and crustal smeltings formed under their influence.

Complex analysis of the geodynamic conditions of the Absheron-Balkhan oil and gas zone

The Absheron-Balkhan oil and gas area is located in the contact zone of the Scythian-Turanian platform with the South Caspian basin (SCB). In recent years, in addition to theoretical considerations, scientists have conducted a number of geophysical studies to determine the structure of sediment cover in the South Caspian Basin. The information obtained about the depth structure has formed a new idea about the formation of the South Caspian basin. The purpose of the work is to study the features of geodynamics of the zone of the junction of the South Caspian basin and the Scythian-Turanian epi-Hercynian platform. The research methodology combines a complex analysis of geological, seismological, geomorphological, and geodetic data on the studied area. Geological and geophysical data in particular on regional profiles were used to link earthquakes to specific geological structures.
 The South Caspian Basin is surrounded by active mountain zones on all sides. The Kopeh Dagh, Alborz, and Talysh mountains, which connect the eastern, southern, and western sides of the basin, are observed with earthquakes not deeper than 30 km. In contrast, earthquakes were observed in the Absheron-Balkhan threshold, which covers the northern part of the basin, at depths greater than 30 km. Tectonically, the Absheron-Balkhan threshold is located at the junction of the South Caspian oceanic crust and the epi-Hercynian Scythian- Turanian continental crust.
 Seismic events, mainly in the northern part of the South Caspian Basin are necessary to study the geodynamic conditions of this area, and to determine the causes of earthquakes. It was observed that the strongest and deepest earthquakes, as well as tectonic processes, occurred in the northern flank of the South Caspian Basin, in the Absheron-Balkhan fold zone, and in the pre-platform area. Analysis of the focal mechanisms and depths of earthquakes proves that they are not specific to collision structures. The high seismic activity of the study area, the observation of crustal deformations at the edges of the basin (based on GPS data), and the development of mud volcanism indicate that the geodynamic conditions of the basin are active. Analysis of the seismic events data shows that the subduction of the oceanic crust of the SCB in the zone of the Absheron threshold under the continental crust of the Scythian- Turanian is the main geological event that caused seismic activity in modern times.
 KEYWORDS: Absheron-Balkhan fold zone, geodynamic conditions, South Caspian Basin, earthquake, deep structure.

Successive accretions of future allochthonous terranes and multiple subduction zone jumps: Implications for Tethyan evolution

Abstract The accretion of future allochthonous terranes (e.g., microcontinents or oceanic plateaus) onto the southern margin of Asia occurred repeatedly during the evolution and closure of the Tethyan oceanic realm, but the specific geodynamic processes of this protracted convergence, successive accretion, and subduction zone initiation remain largely unknown. Here, we use numerical models to better understand the dynamics that govern multiple terrane accretions and the polarity of new subduction zone initiation. Our results show that the sediments surrounding the future terranes and the structural complexity of the overriding plate are important factors that affect accretion of multiple plates and guide subduction polarity. Wide (≥400 km) and buoyant terranes with sediments behind them and fast continental plate motions are favorable for multiple unidirectional subduction zone jumps, which are also referred to as subduction zone transference, and successive terrane-accretion events. The jumping times (~3–20 + m.y.) are mainly determined by the convergence rates and rheology of the overriding complex plate with preceding terrane collisions, which increase with slower convergence rates and/or a greater number of preceding terrane collisions. Our work provides new insights into the key geodynamic conditions governing multiple subduction zone jumps induced by successive accretion and discusses Tethyan evolution at a macro level. More than 50 m.y. after India-Asia collision, subduction has yet to initiate along the southern Indian plate, which may be the joint result of slower plate convergence and partitioned deformation across southern Asia.

Geodynamic issues of ore deposits in Central Asia

The focus of this study is on a pressing issue in ore geology, specifically the geodynamics of ore formation. The paper delineates a comprehensive methodology for examining the geodynamic context in regions hosting endogenous mineralization. The foundation for reconstructing geodynamics lies in geological and structural investigations into the circumstances surrounding mineralization, complemented by outcomes from physical modeling. Tectonic tension and deformation analyses of ore fields and deposits further contribute crucial insights. The study underscores that understanding the geodynamic setting is paramount for elucidating the processes leading to ore formation. This involves a detailed examination of geological structures, conditions of mineralization, and physical modeling results. By adopting this approach, the research provides a robust framework for reconstructing the geodynamic conditions prevalent during the period of ore formation. As a practical application of this methodology, the paper presents results from the reconstruction of the geodynamic situation during the ore formation period in a gold deposit situated in Western Uzbekistan. These findings contribute to a deeper comprehension of the geodynamic processes associated with the formation of valuable mineral deposits, thereby enhancing our ability to interpret and potentially predict similar occurrences in ore geology.

НОВЫЕ ИЗОТОПНО-ГЕОХИМИЧЕСКИЕ ДАННЫЕ ПО КАЙНОЗОЙСКОМУ ВУЛКАНИЗМУ И ГЕОДИНАМИКЕ ПОДВОДНОГО ХРЕБТА ВИТЯЗЯ (ТИХООКЕАНСКИЙ СКЛОН КУРИЛЬСКОЙ ОСТРОВНОЙ ДУГИ)

Original analytical data on rare elements and radiogenic Nd and Pb isotopes in volcanic rocks of the Southern and southwestern part of the Northern Plateau of the underwater Vityaz Ridge are presented. Interpretation of these data and a comparative analysis with published materials on volcanic rocks from the southern and northern parts of the Kuril Island Arc (KOD), which formed on two basement blocks of different genetic nature, allow us to draw the following conclusions. The tholeiite varieties of volcanic rocks of the Southern Plateau and the southern part of the KOD have similar isotope-geochemical features, which point at the general geodynamic conditions of formation and the identical degree of influence of low-temperature fluid on magma-generating processes. The geochemistry of the volcanic rocks of the Northern Plateau, which are mainly represented by subalkaline varieties, indicates a more pronounced participation of the mantle component in magmagenesis and a greater degree of influence of high-temperature melt compared to the rocks of the Southern Plateau, but less compared to the rocks of the northern part of the arc. The volcanics of both plateaus are derivatives of a single mantle source, the MORB of the Indian Ocean (Indian MORB), and were formed together with the rocks of the southern part of the KOD within the lithospheric block transformed by tectonomagmatic processes that accompanied the opening of the Kuril Basin.

Refining hydrocarbon reserve location using modern geodynamics

The paper considers some aspects of the theoretical prerequisites for the influence of geodynamic processes on the distribution of hydrocarbon accumulations in natural megareservoirs. The most interesting part to study is the part of Central Siberia, where quite a lot of large and unique oil and gas fields have been discovered in a relatively small area. It is shown that hydrocarbon deposits in the study area are organized into groups according to the size of reserves. This can be explained by geodynamic processes occurring during the geological history of the region. The features of the river network pattern are interpreted as local geodynamic settings of the «pushed block» type. The relationship between the parameters of local geodynamic settings and the scale of oil and gas accumulation is noted. Keywords: geodynamic processes; large and unique reserves; natural mega-reservoirs; geodynamic conditions; scale of oil and gas accumulation.

Неотектоника и геодинамика зоны сочленения Северо-Западного Кавказа и Черноморской впадины (район г. Геленджика)

Relevance of the work. In the junction zone of the neotectonic structures of the North-West Caucasus and the Black Sea depression, structures of different types in strike and morphological-kinematic type are developed. Determining the structural-geomorphological and neotectonic zoning, including modern ones, and its connection with the sources of tectonic forces and stresses is relevant. Such studies are necessary to ensure the geodynamic safety of engineering structures in the city of Gelendzhik, the territory of which is subject to negative geological processes. The purpose of the research is to identify the structural-geomorphological, neotectonic modern zoning with an assessment of the modern geodynamic conditions of its formation in connection with ensuring the safety of engineering drainage routes in the Gelendzhik region. The research method is structural-geomorphological, with the construction of profiles and geomorphological steps with an assessment of their age and deformations. The work used neotectonic and structural-geodynamic approaches aimed at identifying structures and identifying the sources of stress and deformation fields. The research methodology is the recognition of heterogeneity, different ranks and different ages of stresses and deformations. As a result of the work, erosion-denudation stages of different ages and marine terrace levels and neotectonic structures were identified with an assessment of modern geodynamic conditions. For the first time, a cross-structural plan has been established, in which all-Ural and anti-Caucasian structures intersect. Their origin is associated with the superposition of heterogeneous forces and stresses. Compression stress is generated in connection with collision processes of lithospheric plates and microplates (blocks), tension is generated in connection with the activity of the deep East Black Sea geodynamic system. It considers as a mechanism the upper mantle convection directed from the Black Sea depression towards the orogen of the North-Eastern Caucasus. The superposition of faults of different ages and different types on top of each other causes increased activity in them. Late orogenic faults, consistent with early Alpine (early orogenic) reverse faults, are characterized by increased displacement amplitudes and wide dislocation zones. It is dangerous for engineering routes to cross such gaps. The pipeline at the intersection with the zone of active ruptures will be equipped with special hinge-type devices to prevent dangerous deformations in it.

Prediction of seismic impacts at the site of Plavinu HPP from a potential seismic source in Koknese (Latvia)

The study considers the impact of seismic waves from the source of a potential earthquake in Latvia on the site of the Plavinu hydroelectric power station, which is located in unfavorable geological, tectonic, and geodynamic conditions. A direct seismology problem was solved in two stages to assess seismic impacts on the site. In the first stage, the modeling of synthetic seismograms was carried out, and in the second stage, a prediction of seismic impacts at the hydroelectric power station site was conducted. In the first stage, we used wave field modeling applying Green's method. In the second stage, ground motion characteristics were obtained using a one-dimensional, nonlinear ground response analysis method. A wave field of 15 Green's functions was obtained, which was then converted into a 3-component accelerogram. The accelerogram was then used as a seismic impulse to a Prequaternary sediment's surface. A set of engineering and seismic characteristics of soil was obtained, i.e. amplification, Fourier amplitudes, and spectral amplitudes. The paper demonstrates the ability to acquire valuable information about the seismic wave field and ground motion from macroseismic data from historical earthquakes. This is especially important for intra-plate conditions with limited seismic statistics. Prediction of engineering and seismic conditions are of great practical importance since they will allow us to identify the most vulnerable sites of the soil at the Plavinu HPP.

Geodynamic settings of Silurian - Early Devonian volcanism in the north of the Sakmara zone (the Southern Urals)

The work provides characteristics of the Karamolinsky and Blyavinsky volcanic complexes, which were identified by I.A. Smirnova, V.L. Cherkasov, V.T. Tishchenko, I.B. Seravkin in the Mednogorsk region in the rank of strata. Based on findings of graptolites in limestones and siliceous shales, intercalations among pillow basalts and massive basaltic flows, the sequence is dated as the Middle to Upper Llandoverian. Based on the presence of facies replacement of the Karamolinsky sequence with siliceous rocks of the Sakmara Formation, the age of the Karamolinsky sequence is assumed to be S–D1. The Karamolinsky sequence (according to A.D. Petrovsky, L.D. Chegodaev) is identified with the Blyavinsky formation. We propose that the basalts of the southern wall of the Blyavinsky quarry and their analogues containing interlayers of siliceous rocks with graptolites (S1) be included in the Karamolinsky sequence and Blyavinsky formation, and the ore-hosting section of the Blyavinsky and Komsomolsk deposits with low-titanium basalts and acidic polyfacial rocks, is classified as the Blyavinsky formation (S–D1). The geodynamic conditions for the formation of the Karamolinsky strata are discussed. Materials on the composition and age of the Karamalinsky formation of the Maksyutov complex and pyrite mineralization of the Yuluk group of deposits in the Uraltau zone are considered. It is concluded that it is possible to partially compare the strata of the Maksyutov complex and the Silurian-Early Devonian volcanic sulfide-bearing strata of the Mednogorsk ore region.

Influence of the geotectonic regime on property formation of coal in the northern edges of the Donetsk basin

Purpose. To determine the influence of the geotectonic regime during accumulation of carbon formation on development of coal-bed properties of the northern Donbas. Methodology. To perform the tasks set, a number of research methods were used which include petrographic, chemical and technological, facies and tectonic, computational, statistical and analytical, informational, chronological, genetic, comparative and other methods. Findings. The effect of the geotectonic regime on the formation of coal properties has been established. It is proved that the change in the number of maceral groups is of a regular nature. The reduction in the number of maceral groups of liptinith and irtinitis, in the light of the increase in the number of maceral wind group, is taking place in the direction of the growth of the total amplitude and average speed of the oscillating movements of the Earth’s crust during the accumulation of carbon formation. Originality. Coal formation is considered regarding a unified geodynamic perspective as an integral part of a complex set of natural processes that accompanied the development and interaction of deep structures (plates) of the lithosphere. The main attention is paid to the peculiarities of the composition and quality of coal formed under geodynamic conditions with different motion nature of the lithosphere. For the first time, comparative analysis of the coal-bearing formation of the middle Carboniferous period of the Old and Northern Donbas has been performed. Detailed petrographic and chemical-technological characteristics are given to the coal seams of the Northern Donbas. The peculiarities of the composition and quality of the coal of the deltaic-bog-marine formation have been determined for the first time compared to the coal of other formations of the Middle Carboniferous. Practical value. Regional (“provincial”) peculiarities of coal composition and quality of deltaic-bog-marine and alluvial-bog- marine formations of northern Donbas regions have been defined, which will allow substantiating the directions of its rational use. The proposed approach makes it possible to predict coal content as well as composition and quality of coal in the areas of distribution of bituminous coal. The expediency and prospects of adding the coal of northern Donbas to the fuel base of Ukraine are proven.