Geoelectrical inhomogeneities of the Crimean region as the seismicity and oil-gas potential zones

Abstract

The three-dimensional geoelectrical model of the Earth’s crust and upper mantle of the Crimean region and adjacent territories has been built for the first time. It is based on the results of the Earth’s low-frequency electromagnetic field experimental observations, conducted in 2008—2013 by the Institutes of the National Academy of Sciences of Ukraine. The subvertical conductive zones or contacts of the different resistivity mainly in the near-surface layers coincide with the fault structures, most of which are confined to the boundaries between the different tectonic elements, such as the Scythian Plate and Mountain Crimea, North and South Kerch Zones and the other faults: Chongarskiy, Melitopol-Novotsarytsynskiy, Korsarsko-Feodosiyskiy, Gornostaevskiy and Kerch-Chkalivskiy. The Mykolayiv and West Crimean fault systems occur as large separate submeridional conductive zone. Deeper in the Earth’s crust and upper mantle, geoelectrical inhomogeneities are transformed into the subhorizontal structures (layers) and manifest themselves in regional anomalies. This fact may indicate the high permeability for deep fluids of contact zones during their formation. The deep sublatitudinal structure in the Earth’s crust is confidently traced, in the west it confirms and details the well-known Tarkhankut anomaly, and continues through the central Crimea to the northwestern part of the Kerch Peninsula. It is assumed that there is the strong sublatitudinal anomaly in the interior of the northwestern shelf of the Black Sea and in the northeastern part of the Kerch-Taman Depression at the crust — upper mantle boundary, it is contouring the Crimean Peninsula. The ultradeep fluid manifestation zones obtained according to seismotomography, the conductivity anomalies in the Earth’s crust and the upper mantle, increased heat flow and the spread of the earthquake hypocenters confirm the relationship between the Crimea seismicity and collision processes. It is shown the spatial coincidences of the hydrocarbon manifestations and the isolated conductivity anomalies, which are characterized by subvertical channels galvanically connected to sediments, or subvertical contact zones of different resistivity, which are observed not only in the Earth’s crust but also in the upper mantle layers (60—90, 110—140 km) and may cause the superdeep fluid inflow.