GEOPHYSICAL INVESTIGATIONS IN “STARITE KOLIBI†MARBLE DEPOSIT IN CENTRAL SOUTHERN BULGARIA

The scope of the research is to collect information about presence and locations of marbles in the area of “Starite kolibi” deposit. Around the area of the study, there is information from several boreholes, according to which the following rocks are observed: sandstones, clays, marble. Marbles in the area are transformed limestone and dolomite limestone under the conditions of regional metamorphism. In this research is used Electrical Resistivity Tomography (ERT) as a technique that can detect and characterize layers by exploiting resistivity contrasts between different layers using electrical current. The specific electrical resistance of sandstones, conglomerates and clays is lower because they are strongly saturated with pore water. The marbles on the other hand are among the highest electrical resistance rocks. Thus, the specific electrical resistance of the marble is distinctly higher than that of the clays which allows for their differentiation. In the whole investigated area, the top layer is made of clay and sand mix with small marble pieces and soil. The top layer’s average thickness is about 0,4m. The electrical resistivity measurements are used to “separate” a hard rock (marble) from clay and sandstone into the horizons.