GEODYNAMICS

Abstract

The purpose of the presented work was to model the electrical conductivity distribution in the northwestern part of the Ukrainian shield and to study the relationship of geoelectric anomalies with natural mineral deposits and with signs of possible tectonic activation of long-lived fault systems on the Shield. The methodology was based on long-period magnetotelluric and magnetovariational measurements in the period range of 3-16 to 2500-3600 s. The dense network of measurement sites made it possible to explore the geoelectric structure of the Ukrainian Shield segment limited by the coordinates 26°-30°E and 48°-51,7°N. 2D and quasi-3D inversion of the obtained magnetotelluric and geomagnetic responses resulted in the creation of overview models of electrical resistivity/conductivity for the territory of investigation. As a result, geoelectrically anomalous structures were identified at different depths. The local character of the conductors and their position indicate their connection with recently activated fault zones, their junctions and with metallogeny. The Precambrian age of crystalline rocks of the investigated area refers mainly to the electronic-type graphite-sulphite origin of increased conductivity, however the depth of conductive features, their vertical extent and their link to rejuvenated fault systems may indicate the genetic connection of various minerals and their subsequent precipitation with deep fluid migration. Originality. The obtained results aimed at clarifying the deep structure and correlating the geoelectric features of the earth’s crust and upper mantle with fault systems and deposits of various natural mineral sources. In addition, they alone can serve as further evidence of possible tectonic activation processes in the studied area. Practical significance. The presented results can bring social benefits by identifying areas of mineral endowment, and in the field of geodynamics they can contribute to the assessment of natural hazard in mapping the course of tectonically active fault systems.