Mantle gravity anomaly and recent activation in the territory of Ukraine

Abstract

The study of the zones of modern activation on the territory of Ukraine for a long time was carried out using a complex of geological and geophysical methods. Each of them is not without its drawbacks. The results obtained allowed us to assume that the determination of the mantle anomaly of the gravitational field can be eliminated their significant part and serve as a unified criterion for identifying the zones of modern activation. For this, it is necessary to improve the methodology for calculating the effect of the earth’s crust, supplementing it with taking into account the degree of catagenesis of part of the rocks of the sedimentary layer, the effect of increased concentrations of ore minerals in the depths of regional magnetic anomalies, etc. Thus, a more accurate calculation of the effect along the DSS profiles can be achieved. In addition, it is necessary to ensure the determination of the gravitational effect of the crust in the area between the profiles. Kriging technology was used to solve this problem. It allows you to calculate the predicted values of the parameter using those known in other points and to estimate the error of the result. In our case, the usual kriging option was sufficient. To determine the errors, instead of the commonly used variograms, a comparison of data on one of the DSS profiles with those calculated by kriging from information on adjacent profiles was used. The resulting error turned out to be quite understandable, taking into account the errors of the initial data, and acceptable for using the results for mapping the mantle gravity anomaly, and, consequently, the zones of modern activation of Ukraine. The constructed map demonstrates some difference in the location of the anomaly (and, accordingly, the recent activization — RA zones) from the previously established one. In particular, the anomaly is absent in the Desnyanskiy basin of the Dnieper-Donetsk depression. Actually, the gravitational mantle anomaly was absent there before, the spread of the RA zone into the basin was indicated by other criteria of low reliability. It is possible to record the presence of an anomaly in the territory between the Azov and Donbas regions, where it was not previously diagnosed. This result still needs to be supported by additional data. First of all, due to the observed significant discrepancies between different variants of velocity sections along the DSS profiles.