Application of electrical resistivity tomography (ERT) in the Zawiercie Zn-Pb ore area as a source of information on the geological structure

The depletion of Zn-Pb ores in developed mining areas and the increase in metal prices have resulted in the need to search for new deposits which have not been exploited yet. A project of drilling new exploratory boreholes should be preceded by an interpretation of archival geological data. To obtain the most valuable information on the geological structure leading to its plausible interpretation, it seems to be purposeful and advisable to apply some geophysical methods that are reasonably cheap in comparison with others. The method of electrical resistivity tomography, which in this research uses two of many measurement protocols such as Schlumberger array and dipole-dipole array, is particularly useful. Computer interpretation of geophysical results allows a high resolution 2D and 3D geoelectrical model of rock mass to be created. The study was carried out using the multi-electrode Lund Imaging System manufactured by ABEM, Sweden. In order to evaluate the practical application of this method, Zawiercie Zn-Pb ore deposits were chosen as the area used in previous scientific research. Taking into account mineralization in its economic aspect, the deposits occur at relatively shallow depths of 50-120 m. In the investigated region, the Triassic carbonate formation overlays the Devonian rocks. The Keuper low-resistance clay, occurring on the surface, provides a very good electrical contact between an electrode and the soil. This is why there are favourable measurement conditions in this area. The boundaries between the Keuper, Devonian and Triassic formations are clearly noticeable in the resistivity cross-sections obtained. On the basis of the ERT results, it is possible to locate faulting zones as well as karst systems. One of the profiles clearly shows the occurrence of a low-resistance anomaly correlated with Zn-Pb mineralization, which was confirmed by borehole surveys. However, this early stage of the research with the use of the ERT method cannot unequivocally identify the ore body, particularly as it was conditioned by the limited depth of prospecting