| Abstrakt: |
The purpose of the work is to build a three-dimensional P-velocity model of the Earth's crust and upper mantle of the territory of Ukraine. The mantle part of the model was created by the thermal model. The methodology includes the use of correlations between velocity and temperature and the presence of melt under different pressure conditions for typical mantle rocks. Such a model was created for the first time. It is based on a previously constructed scheme of deep processes of various ages in the tectonosphere of Ukraine, which primarily takes into account the results of heat and mass transfer during recent activation (RA). Results are superimposed on the models of the platform (the territory of the East European Platform, and the Donbass), the Alpine geosyncline of the Carpathians, and the Hercynian-Cimmerian geosyncline of the Scythian plate. The incomplete process of recent activation cannot be accurately described by the geological theory used by the authors. To select an adequate heat and mass transfer scheme, gravity modelling was previously carried out on a system of profiles around the northern hemisphere with a total length of more than 50,000 km, crossing Eurasia, North America, the Atlantic and Pacific oceans. A process scheme that best corresponds to reality (observed gravitational field) has been identified. The scheme is used for Ukraine, where the activated area is determined with great accuracy. In the south, the model is limited by the Black Sea depression, at a depth of 400 km. Velocities in the transition zone to the lower mantle were not taken into account. The values of P-velocity at each depth in the mantle were determined by the difference in temperature from the background (platform) one. The melt concentration at temperatures above the solidus was considered minimal (about 1.5%). It corresponded to a decrease in velocity by 0.1 km/s. Test velocity models were compared with specially selected independent ones. The error (0.035 km/s) of the calculation and the isoline section (0.1 km/s) for depths from 50 to 150 km are determined. At a depth of 25 km, the model was constructed using DSS data. Error – 0.13 km/s. The cross-section of the isolines is 0.4 km/s. The differences in velocity under the non-activated platform from the centers of recent activation zones reach 0.6 km/s at depths of 50-100 km, 0.1 km/s at depths of 150- 300 km, and 0.2 km/s at depth of 400 km. The results of modelling will make it possible to build schemes of tectonic processes at a more detailed and reasonable level, which will allow us to reliably predict the level and features of the seismic situation for the entire territory of Ukraine. [ABSTRACT FROM AUTHOR] |
