Complex Geophysical Prospection – Electrical Resistivity Tomography and Geomagnetic Survey for Detecting Limestone Inclusions in Mini Maritsa Iztok Ead

Abstract

The presence of consolidated limestone inclusions in Mini Maritsa Iztok EAD has great influence on the pace of productivity and becomes an issue of primary importance. Complex geophysical prospections were performed in order to collect information about the presence, location and characteristics of the solid limestone bodies incorporated in the mostly clayey medium. The use of selected high-resolution geophysical methodselectrical resistivity tomography (ERT) and geomagnetic survey proved to be very effective in the non-destructive survey of the investigated area.Keywords: electrical resistivity tomography (ERT), geomagnetic survey, electromagnetic field, limestone inclusions. INTRODUCTIONMini Maritsa Iztok EAD is the largest coal mining company in the Republic of Bulgaria. It works the Maritsa Iztok lignite field. Coal seams in the Maritsa Iztok basin are located relatively low at 6-10 m to 110 -120 m below the surface. The total thickness of the coalfield complex is around 35 -40 m and is divided by clay layers into three seams. The medium (second) seam is the main coal carrier with an average thickness of 15 -25 m. The deposit is operated by three opencast mines -Troyanovo-1, Troyanovo-North and Troyanovo-3. The present study helps in understanding the geological conditions in opencast Troyanovo-3. Troyanovo-3 mine is located in the southern part of the Maritsa Iztok Basin and is in the form of a rectangle with west-east orientation, a length of 12 kilometers and a width of about 2,5-3 km. The payable reserves are calculated at 336,230,000 tonnes. The coal layer is located at an average depth of 70-80 m. Extraction conditions in the opencast Troyanovo-3 become harder because of presence of solid limestone inclusions. These solid limestones bodies make extraction operations extremely challenging. This study is focusing on opencast coal exploration in the area of Mini Maritsa Iztok EAD. The usefulness of geophysical methods in mapping the hard rock inclusions in the overburden of the lignite mines is outlined.

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