Geophysical Survey of Selected Mine Dumps in Ostrava

Abstract

In the past, primarily, mineral deposits have been extracted for economic gains with very little attention paid to the exposure of the waste rock material (tailings) to the environment after mining is completed. Due to the mad rush of these economically beneficial minerals, many mine dumps were created with tons of tailings piled up at locations as the years go. In the past, miners and geologists paid very little attention to dumps site morphology which is now a cause for concern. In the Czech Republic, coal mining dates to the 19th Century, and 71% of the dumps because of coal mining are in the Ostrava-Karvina Region. In recent times, many geological, geochemical, and geo-engineering studies have been carried out to classify these dumpsites because of some striking peculiar characteristics these dumps display. It is against this backdrop that we choose to apply the electrical resistivity surveying method to determine the geophysical properties of some selected dumpsites in this region. The geoelectrical resistivity survey method was carried out in three dumpsites, the Heřmanice dumpsite (thermally active), the Oskar and Hrušov dumpsite (thermally dormant dumps). For the thermally active dump, the geophysical resistivity ranged between 8 and 36316Ωm. The resistivity responses in this dumpsite suggested two formations with different resistivity (Low resistive and high resistive zone). The low resistive zone was further reclassified in to 2 layers, a partially saturated topmost layer of about 10m of depth having fairly high resistivity and a fully saturated bottom layer having very low resistivity. High resistivities encountered could have been due to the presence of a sulphate cap, and highly compacted tailing materials metamorphosed due to burial pressures, and high temperatures from self-ignited tailings. Low resistivities could have been caused by fluids within the pore spaces of the spoils. The Oskar and Hrušov dumps displayed lower resistivities than the Heřmanice dumpsite. Both dumps had zones of high and low resistivity with the high resistivity layers suggesting highly dense tailings materials and the presence of a sulphate cap, while low resistive layers suggested porous tailings materials saturated with water. The Oskar dump displayed about 85% of it spoils having high resistivities while this was not the case for Hrušov dumps. Resistivities vales of 1 interpreted from the resistivity profile of Oskar dump suggested minimal sulfides leaching.