GEODYNAMICS

The aim of the research presented in this article is to analyze the properties and geological informative value of the anisotropic transformations of gravitational and magnetic fields, which use averaging procedures, including analysis of Andreev-Klushin's method. Anisotropic transformations of potential fields are designed to detect and track elongated anomalies or their chains, caused by deep linear dislocations in the geological section. The study of the anisotropic transformations properties is based on the analysis of their depth characteristics, as well as theoretical and practical experiments. The study applies the analysis method of fault tectonics reflection features in anisotropic anomalies of gravimagnetic fields, in particular, on the example of the South-East of the Ukrainian Carpathians. It is based on the search of morphological signs of manifestation of deep faults and other long structural-tectonic dislocations in gravitational and magnetic anisotropic anomalies. The method also suggests tracing these elements, relying on the comparison of morphology, intensity, size and direction of anisotropic anomalies with published regional tectonic and geological maps. Results. The paper presents definitions and algorithms of such anisotropic transformations as Andreev-Klushin's methods of anticlinal and terrace types, anisotropic averaging and anisotropic difference averaging. The research allowed us to perform study of the geological informative value of anisotropic transformations of potential fields on theoretical and practical examples. It is shown that in the morphology of anisotropic gravitational and magnetic anomalous fields in the south-east of the Ukrainian Carpathians long local anomalies are traced. They are caused by fault tectonics, in particular deep longitudinal and transverse faults, as well as linear complications into sedimentary cover. The analysis of anisotropic anomalous fields reveals a number of characteristic features of large tectonic zones reflecting regional behavior of the foundation surface and deep faults; on its basis fault tectonics schemes of the South-Eastern region of the Ukrainian Carpathians can be constructed. The study traced a significant extension of the foundation of the Eastern European platform from the Maidan's ledge and the Pokutsko-Bukovynian Carpathians under the Folded Carpathians. The definition of a number of anisotropic transformations is given and their properties are considered. The work substantiated geological informative value of the anisotropic transformations morphology of potential fields in the study of the Ukrainian Carpathians and adjacent depressions fault tectonics. The use of anisotropic transformations of potential fields will increase the reliability and detail of tracing deep faults, as well as other linear dislocations both in the foundation and in the sedimentary cover. The study of fault tectonics is an important factor in the successful solution of problems in the search and exploration of areas which are promising for oil and gas deposits.

Geological structure of central Vietnam by interpretation processing of gravitational survey data using the “COSCAD 3D” computer technology

Background. The central regions of Vietnam are of strategic importance for the Republic, being, in fact, the gateway to the ASEAN countries. Investing in the exploration and evaluation of mineral resources, in particular ore minerals hidden at great depths, is a specific and necessary task for the country.Aim. To clarify the structural-tectonic scheme of the analysed area and to identify the main fault systems and zoning of the Central Vietnam area by the gravitational field based on classification algorithms.Materials and methods. The objectives were achieved by assessing the total gradient of the gravitational field, analysing the distribution of the field variance and the results of tracing the axes of the gravitational field anomaly. Interpretation processing of gravity data was carried out using the “COSCAD 3D” computer technology of statistical and spectral correlation data analysis.Results. The defined fault systems, which play an important role in the processes of mineral formation, have a northwestern, northeastern and latitudinal strike. The zoning of the study area according to the gravitational field, its characteristics and available geological information made it possible to identify 13 homogeneous areas. Each area is characterised by a certain level of gravitational field, the values of dispersion and total field gradient, as well as correlations between attributes. The classification results confirms the complexity of the geological structure of the area under study and the presence of three main strikes of the systems of tectonic dislocations – northwestern, northeastern and latitudinal.Conclusions. A large number of tectonic dislocations of various strikes and intensities, revealed using the methods of the probabilistic-statistical approach, implemented in the “COSCAD 3D” computer technology, indicates that the area under study is promising in terms of ore deposits.

Nickel anomalies and gold-quartz mineralization in dunite-harzburgite massifs of the Pervomaisko-Verkhoturinskaya area, Central Urals

Along with some gold-quartz deposits hosted by dunite-harzburgite massifs elsewhere in the Urals, elevated Ni concentrations were revealed within the ore field of the Anna gold-(sulfide)-quartz deposit localized in weathered oxidized dunites and harzburgites of the Pervomaisky complex (συO2p) in the Pervomaisko-Verkhoturie district of the Central Urals. The spatial association of Au and Ni concentrations in dunites-harzburgites may be attributed to a partial inheritance of Ni-controlling tectonic dislocations by those hosting gold mineralization. Therefore, the combination of halos of Ni and Au concentrations in dunite-harzburgite massifs is a favorable indicator of areas prospective for discovery of goldquartz mineralization.

TECTONIC EVOLUTION OF THE WEST-PACIFIC REGION: FORMATION OF LITHOSPHERIC VORTEXES

Using the example of the West Pacific Segment of the Earth, the interrelation of vertical and horizontal tectonic movements is considered – the most important and far from being solved at present problem of geotectonics. An overview of the concept of the global ordering of various forms of the earth's surface as an end result of the action of geodynamic forces is given. The author's developments concern the issues of the origin of structures associated with the interaction and influence of endogenous forces on the formation of a regional relief. The main tools for its study were structural-geomorphological methods and lineament analysis. It has been established that: 1) all tectonic dislocations contain both horizontal and vertical components of the velocity of movement, and the former dominate in the structure formation of the region; 2) the end result of their interaction is vortex and other nonlinear (ring, spiral, arc, etc.) deformations of the lithosphere, which constitute the main type of structural elements of the region; 3) they are often accompanied by magmatic activation of the tectonosphere in the form of convective movements and / or «floating» of plumes; 4) the sea and oceanic depressions of the Western Pacific are, in essence, funnels of convective cells, which, under the conditions of shear velocities of the movement of interacting geoblocks of the lithosphere, were structured into the form of tectonospheric eddies. A model of convection of a three-layer tectonosphere is proposed, the movement of which in the gravity field is caused by local decompaction and a decrease in the viscosity of a piecewise inhomogeneous medium. The outlined concepts allow us to consider the tectonic evolution of the West Pacific region as the formation of a lithospheric mega-vortex in the continent-ocean junction zone. Its development is associated with the energy interaction of the mantle and the upper shells (tectonospheres) of the Earth, which is due to the unstable regime of the planet's rotational dynamics.

Studies of Natural Soil Radioactivity in the Kirchhoff Hill (the Leningrad Region, the Russian Federation)

From the geoecological point of view, a special place in the geological section of the Kirchhoff Hill is occupied by highly radioactive geological bodies – dictyonema oil shales. As a result of glacial tectonic dislocations and due to numerous local elevations and depressions in the relief, dictyonema oil shales can come into direct contact with the soil over relatively large areas here. Based on the results of the route survey of the gamma field over the soils of the Kirchhoff Hill in the zone of anomalously high exposure dose rate, we laid a pit. Seven samples were taken and analyzed from the depth of 0 to 85 cm. The first two samples (0– 25 cm) correspond to the gray-humus dark-profile soil on dictyonema oil shales type. Here, the average value of the specific effective activity (Aeff) makes 1,750 Bq/kg. The average Aeff of the next 5 samples of dictyonema oil shales (25–85 cm) makes 1,870 Bq/kg. Such radioactivity values belong to the environmental hazard class IV and impose significant restrictions on building and construction in the area of studies.

EVOLUTION OF CONCEPTS ABOUT THE STRUCTURE OF OIL AND GAS TRAPS IN THE STUDY OF PETROLEUM BEARING SUBSURFACE RESOURCES IN WESTERN YAKUTIA

The article presents the development history of the oil and gas industry in the Republic of Sakha (Yakutia). It is shown that during the first seismic exploration, prospecting for fields was carried out exclusively in the lower reaches of the Vilyui River. These works made it possible to identify the large Khapchagai gas region in Mesozoic deposits in the eastern Vilyui syneclise and discover a number of gas fields. Traps on them are typical platform structures - brachyanticlines with first degrees of dips, without any traces of disjunctive tectonic dislocations. The latter are predicted here lower in the section, starting from the Permian top. Scientific concepts of oil and gas traps revealed in various years in Western Yakutia in the course of geological exploration, from the period of inition of the oil and gas geophysical service in the republic (1950) to the present, are considered. The evolution of concepts of the oil and gas trap structure is shown, using the example of Srednebotuobinskoye and Verkhnevilyuchanskoye fields. This evolution was carried out in the process of geological exploration due to a more complete record-keeping of disjunctive disllocations and their role in the structure of traps.

Prospects of paleomagnetic studies of the Riphean intrusive bodies of the Bashkirian megazone (Southern Urals)

<p>         The studied objects are located in the core of the Bashkirian megazone and related to the Riphean stage of rift magmatism of the East European craton. Paleomagnetic studies of the Bashkirian megazone intrusive bodies can be a source of new information on the East European platform position in the Riphean, as well as on the process of remagnetization during the Late Paleozoic folding on the Southern Urals. At this moment, 42 thin basic intrusions and the Main Bakal dyke were investigated.</p><p>         According to the results of our previous paleomagnetic studies two remanence components were isolated in Bashkirian megazone intrusions. First, the primary remanence component of Middle Riphean age was isolated in 8 thin bodies. Pole for the boundary of the Early and Middle Riphean of the East European Craton was calculated from high-temperature component of remanence of 8 sheet intrusions. This pole is close to the known paleomagnetic poles of East European craton for close ages and agrees with U-Pb age of one of the studied bodies (1349 ± 11 Ma). Also, arguments in favor of the primary origin of the remanence and the absence of significant tectonic dislocations in the sampling area are discussed. In other 4 intrusive bodies, paleomagnetic directions that are close but slightly different from the Middle Riphean directions were found. Second, the Late Paleozoic directions were found in the studied objects. These directions are widespread in the Bashkirian megazone rocks and have been reported by other researchers. Presumably it is the result of the Late Paleozoic syn-collisional remagnetization.</p><p>            According to the new results another component of remanence was detected in the intrusive bodies of the Bashkirian megazone. In 2 sheet bodies and the Main Bakal dyke a component close to the Late Riphean identified earlier in sedimentary rocks of the same region was found (Pavlov, Gallet, 2009; Danukalov et al., 2019). Furthermore, in total 20 thin intrusive bodies and the Main Bakal dyke have paleomagnetic directions close to the Late Paleozoic directions. The comparison of mean paleomagnetic directions for the different studied regions demonstrates the absence of any traces of essential rotation of blocks within the Bashkirian megazone in the Later Paleozoic.</p><p>            At this moment the origin of the remanence of 8 thin bodies is unclear, the nature of the other components of remanence requires additional research. It is planned to sample more intrusive bodies and to perform the isotopic dating of the key objects.</p><p>References:</p><ul><li>1) Pavlov V.E., Gallet Y. Katav limestones: A unique example of remagnetization or an ideal recorder of the Neoproterozoic geomagnetic field. Izvestiya, Physics of the Solid Earth, 2009, vol. 45, no. 1, pp. 31-40</li> <li>2) Danukalov K. N., Salmanova R. Y., Golovanova I. V., Parfiriev N. P. New paleomagnetic data on sedimentary rocks of the Inzer and Zilmerdak formations in the Southern Urals// Materials of the XXV anniversary All-Russian School-Seminar on problems of paleomagnetism and magnetism of rocks. – IPE RAS Moscow, 2019. – P. 108-113</li> </ul>

PARAGENESES OF ORE ELEMENTS IN CARBONATE ROCKS JUNCTION ZONE DONBASS AZOV BLOCK UKRAINIAN SHIELD

Purpose. Study geochemical composition and parageneses ore elements in carbonate rocks articulation zones Pryazovskyi crystalline array Donetsk folded structure. Methodology. Complex statistical methods used SPSS / v19.0 for Windows package – namely, correlation and cluster analysis in determining the parageneses of ore elements in carbonate rocks. Results. The article studies carbonate rocks in which ore occurrences and areas of secondary mineralization distribution were previously established. Statistical data processing of semi-quantitative spectral analysis of samples was carried out. The statistical characteristics of the distribution of ore elements in primary carbonate (limestone, dolomite) and karst zones rocks are determined. An increase in the coefficients of variation and concentration of ore elements in karst formations has been established. It is concluded that an increase in the permeability of carbonate rocks in leaching zones is accompanied by the activation of hydrothermal-metasomatic reactions and contributes to the localization of ore occurrences of secondary mineralization (fluorite, quartz, sulfides). Leaching zones, next to zones of tectonic disturbances, served as the leading channels for hydrothermal solutions, under the influence of which substitution reactions of the main cations of carbonate rocks by ore element cations took place. Repeated activation of hydrothermal processes led to the formation of mudstones. Tectonic dislocations were accompanied by the formation of low-temperature associations of hydrothermal minerals. There are the higher-temperature associations of hydrothermal minerals in carbonate rocks on the areas of andesite-trachyandesite complexes igneous rocks distribution. Scientific novelty. It was established for the first time that the ore occurrences of the Donbass Junction Zone with the Priazovsky block of the Ukrainian Shield can be attributed to the hydrothermal mudstone formation, and their localization is determined by the presence of decompression zones in carbonate rocks. Practical significance. The regularities established can be used to predict leaching zones in carbonate rocks, where there is a decrease in the quality of carbonate raw materials. Key words: Associations of ore elements, concentration coefficients, hydrothermal mineralization, leaching zones, tectonic dislocations, mudstone formation.

Perspective of gold-bearing deposits in the ferruginous-siliceous formations of Egypt and Kursk Magnetic Anomaly

Banded ferruginous-siliceous formations (FSF) are confined to the Precambrian basement of the Arabian-Nubian Shield within the central part of the Eastern Desert of Egypt. Gold mineralization is spatially associated with banded ferruginous quartzite, representing one of the most ancient manifestations of gold ore. The Precambrian rocks are combined into deposits complex of the Neoproterozoic Pan-African megacycle of the territory development. Banded iron-silicate rocks occur in sedimentary-volcanogenic rocks that were formed in the subduction trough zones, and are represented by metamorphosed ferruginous quartzites, jaspilites and schists. FSF show tectonic dislocations, shear cracks, and fracture cracks made by gold-quartz-sulphide mineralization. Promising for the identification of gold-bearing mineralization in the rocks of the FSF can be iron-silicate deposits with the occurrence of epigenetic hydrothermal activity as a result of activation of the submarine volcanism of the tholeiitic type.