Suchergebnisse

As a result of paleomagnetic studies Sariolian 2,4–2,3 Ga conglomerates of the Onega basin of the Karelian protoctaton, two characteristic components of magnetization have been separated. Mean direction of the medium-temperature component has a heap distribution and coincides with mean direction of the Svecofennian remagnetization within the Karelian protocraton. The directions of high-temperature magnetization components isolated in conglomerates have a significant spread, which indicates the primary nature of this magnetization component. Two clusters of high-temperature components associated not only with the composition of protolites, but also with different conditions of rock transformations, including their fluid saturation, are distinguished.

New paleomagnetic and isotopic-geochronological data obtained for Neoarchean Onega granulite complex, were used to reconstruct the position of the Karelian craton in the Neoarchean supercontinent Kenorland. Geological correlations were made for the Karelian, Kaapvaal, Pilbara, Superior, and Slave cratons. Comparison of independent geological and paleomagnetic data allowed us to propose a new configuration of the Neoarchean supercontinent Kenorland. The position of the ancient core of the Karelian craton (the Vodlozero terrane), located in the North-Western margin of the supercontinent structure, reconstructed based on the previously paleomagnetic data for the Neoarchean Panozero sanukitoid massif and new one for granulite of Onega complex.

The secondary (metachronous) component of magnetization isolated in the Precambrian complexes of the Karelian craton have been analyzed. The mean directions of high temperature components (deviations from the true direction) depending on the contribution of secondary magnetization components resulting from uneven-aged tectono-magmatic events. It has been shown that the Precambrian key poles often coincide with the vector sum of the ages of Phanerozoic component of magnetization. The conclusion about the primary/secondary origin of the Precambrian paleomagnetic poles must be set on the basis of the integrated petro-paleomagnetic and isotopic data and geological correlations, not only tests of paleomagnetic reliability.

This paper deals with the complex geophysical studies carried out to determine the nature of the intense magnetic anomaly identified by the results of ground surveys on the right bank of the river Slushka on the territory of Yukhnovsky district of Kaluga region. Integrated interpretation of geophysical data and laboratory core measurements allowed to define the nature and parameters of the anomalous object located in the upper part of the section and presented by loam containing such magnetic minerals as greigite, pyrrhotite and magnetite.

Volcano Girvas is a complexly constructed volcano complex of the Yatuli age. Apparently, it is a shield lava volcano, which was probably one of the supply channels of the vast lava field of the western Prionezhie region within the Girvas volcanic zone. Despite the fact that the Girvassky volcano is bare only fragmentary, the structure of the current is perfectly preserved in the rocks, allowing to reconstruct the direction of flow. Among these rocks, there is a zone of postvolcanic hydrothermal changes in the rocks, consisting mainly of nesting and veined tourmalization and silicification, as well as subsequent epidotization, sulfidization, chloritization and albitization. The zones of secondary changes are confined to faults, while their spatial-temporal correlation remains unclear. Reconstruction of the geological structure showed that there were two main processes at the Girvasa volcano: 1) pneumatolysis of type due to magmatic gases separated from gabbro-dolerite sills, 2) heating and circulation of exogenous waters with formation of near propylites. Based on the proposed scheme, thermodynamic modeling was performed.

Presents the results of magnetotelluric soundings acquired in 2020 along the profile Rzhev– Velikie Luki, in the suture zone of three parts of Precambrian crust of East European platform: Fennoscandia, Sarmatia and Volga–Ural. In the central part of the profile, anomaly zone of increased conductivity in the crust was revealed. The crust conductor is weakly expressed on the components of the telluric tensor due to the screening effect of the conductive sedimentary cover; therefore, the focus in the qualitative analysis of data and inversion was made on magnetovariational parameters.According to the results of two–dimensional inversion carried out in the program of A.E. Kaminsky ZONDMT2D, on the geoelectric model a subvertical zone of low resistivity in the crust is identified, which is probably associated with the paleosubduction zone of the Belarusian Ocean Plate.

As a result of integral investigation of the Paleoproterozoic magmatic complexes the trend of remagnetisation has been obtained. The direction of remagnetisation was propagated from North-West to the South-East. Probably, the new trend of remagnetisation reflects the strike of Paleoproteorozoic collision. Correlation between remagnetisation processes and composition of the rocks have been deduced. Probably the extent of keeping of early and late secondary components is caused not only with protolithic composition but with different transformations of the rocks including whose fluid saturation.

A complex of geological and geophysical work was carried out to study fracturing in the Jurassic-Neogene rocks of the Heraclea Plateau, which included a field study of the Georgievsky fault zone, structural and geomorphological analysis; the geophysical complex combined marine seismic and magnetometric studies in combination with ground-based studies using electrotomography, gravimetry and magnetometry. The main object of study was the zone of the deep Georgievsky fault and the feathering tectonic disturbances. As a result of complex studies, the main geological and geophysical criteria for the identification of dangerous fracturing sites have been established: the extremely heterogeneous structure of the upper part of the geoelectric section to depths of 30–40 m according to electrical survey data; seismic data indicate that Miocene limestones have extremely low strength properties in areas of increased fracturing; according to electrical survey data, the water content (humidity) of the upper part of the section changes sharply horizontally; in the karst areas at certain depths, there is a sharp variability in resistivity from the maximum values to the minimum; fracturing develops quite actively under the influence of landslide processes. Especially dangerous are the stretching cracks that occur in areas of positive relief of the base rocks, along which landslide bodies represented by limestones slide.