Nº 2 (2025)

Mapping of hydrothermal-metasomatic alterations in the Ahaggar, Southern Algeria, was first performed using the Landsat 8 satellite imagery. This area is promising for gold mineralization. The objective of the study was to identify similar patterns in the distribution of hydrothermal-metasomatic alterations to develop forecast and exploration criteria for the gold ore type of mineralization. Thus, it was established that the areas in the Ahaggar Shield promising for gold mineralization localized along and/or inside the transregional fault zone, which controls ore mineralization confined to the periphery of large morphostructures (400 to 800 km in diameter) of the 1st order. Such morphostructures should be complicated by ring, arc structures of the 2nd and higher ranks and faults of NNW and NNE strikes with a length of more than 100 km, or weakened zones along which intrusions of dikes of medium (gabbro-diorites, diorites) composition associated with gold ore mineralization are recorded. In addition, metasomatic halos of a significant area (more than 30 km²) with increased values of indices of oxides of di- (magnetite) and trivalent iron (hematite), and to a lesser extent oxides and hydroxides of iron (limonite) and hydroxyl- (Al-OH, Mg-OH), carbonate-containing minerals and oxides should be manifested in potentially ore-bearing volcanic structures.

The spatial distribution of the lithospheric magnetic anomalies Maps of the spatial distribution of the lithospheric magnetic anomaly field for three hot spot areas: Hawaii, Afar and Iceland were analyzed in order to solve the interdisciplinary problem of the hot spots and mantle plumes impact on the lithosphere. To construct the plume and hot spot magnetic images the experimental data of the CHAMP satellite was used which were obtained in the last year of its operation, 2010, at a minimum level of 280-260 km. The database of the anomalous magnetic field parameters has been supplemented for areas where materials on these hot spots were already available, and new data has been obtained for the part of the Pacific Ocean where the Hawaiian hotspot is located. Maps of lithospheric magnetic anomalies have been constructed for the central Pacific Ocean, the East African rift zone and the North Atlantic. It is shown that magnetic images of the various types of hotspots: oceanic Hawaiian, continental Ethiopian and island Icelandic appear themselves in different ways, which reflect the consequences of tectonic processes that took place earlier and are currently developing in the territories under consideration. It is shown that the use of satellite observations of the lithospheric magnetic field in areas with mantle plume activity when being combined with other geological and geophysical regional data could add considerable information to the overall picture of the tectonic processes study.

The activation of thermokarst processes due to climate warming over the past decades in the permafrost zone is observed almost everywhere. Numerous studies are dedicated to examining these processes, with special attention given to the quantitative patterns of thermokarst lakes and their dynamics. The goal of this research was to analyze the dynamics of thermokarst lakes and assess their quantitative characteristics based on satellite imagery, as well as to explore the relationship between the dynamics of thermokarst lakes and climate changes. The study was conducted using a section of the Yana-Indigirka Lowland in northern Yakutia, based on a series of satellite images from Corona, Landsat 7, and Sentinel-2 over six observation periods: 1966, 1976, 1999, 2007, 2013, and 2021, as well as the ArcticDEM digital elevation model (2 m/pixel). A total of 248 lakes and 303 alas depressions were identified in the study area, and the lakes were classified into six main types based on their form and location. The research revealed a general increase in both the area and number of lakes over the entire observation period, although the dynamics of the lakes were variable. Residual lakes within alases consistently showed a decrease in area, indicating further drying, whereas thermokarst lakes within alases grew in 1976 and 2007, but in other years, their overall area decreased. In 1999 and 2013, lake areas increased by 3.1% and 20%, respectively, while in other years, there was a slight reduction in lake area. The total number of lakes increased by 90 by 2021. New lakes were noted in class of lakes outside the alases and lakes in alases categories. There was also an increase in the number of class of residual lakes, indicating the drying of lakes in other classes and their transformation into residual lakes within alases. The emergence of new alases was observed in 1976, 2013, and 2021, indicating the drying of some lakes and a reduction in total lake area. An analysis of temperature anomalies shows a general increase after 1999, with this period also marking the beginning of the rise in the number and area of lakes.

The structural features of the Yukki-Toksovskaya zone of strike-slip faults are considered. The results of the analysis of satellite images of the Yukki-Toksovskaya zone allow us to take a different look at the latest tectonics and geology of the area. The materials show a lens-shaped shear zone, which is atypical for the platform area. Inside the fault zone, bodies of giant tectonic breccia are mapped in the form of rhombohedrons, which are uncharacteristic for this area. The Yukki-Toksovo zone has been studied using structural analysis methods at the level of axial fault zones and fault planes. A description is given of the outcrops located on the fault axes or their wings. The kinematic types of faults are justified by studying the position of thrusts on their wings. A spectral seismic profile across a seismogenic scarp and one of the faults is presented. The magnitudes of vertical and horizontal movements along faults were measured based on the displacement of rocks of the marker horizon. Vertical fault planes have been studied and their genetic connection with thrust faults has been revealed as the development of a single shear zone. Zones of shear failures of several types were discovered. Shifts and thrusts have been identified in the near-surface part of the section of Upper Quaternary deposits. The faults of the Yukki-Toksovo zone are defined as left-lateral strike-slip faults. A preliminary assessment of the velocities of horizontal movements along the faults of the Yukki-Toksovo zone has been made. It is proposed to use the territory of the Yucca-Toksovo fault zone as a testing ground for studying Holocene paleoearthquakes.