Namibia AEM Mapping: A case study of Airborne EM data used as a geological mapping and interpretation tool

Abstract

The Geological Survey of Namibia hosts a world leading airborne geophysical data coverage library that has amassed from years of large scale regional airborne magnetic and radiometric survey acquisition with detailed high resolution survey follow up to promote the exploration and mineral wealth of the country. In 2005 the Geological Survey of Namibia acquired a strategically planned Airborne Electromagnetic Survey in Northeast Namibia. Following completion of this initial phase one reconnaissance survey (532 line km), two areas were selected for detailed high resolution follow up, namely Elandspan and Eiseb. In total just over 5,000 line km of AEM was acquired. Initial qualitative interpretation indicated that the Tempest AEM system could detect conductors beneath the Kalahari sediments. Recently a more detailed interpretation has been undertaken with many 2D and 3D mapping products generated. Conductivity Depth Images along with early, mid and late time EM products were created illustrating the surficial effects of a river system and a number of deep basement conductors. The 2D and 3D AEM products led to an integrated geological interpretation of the area and significantly added value to an aeromagnetic interpretation of the area. The CDI?s generated allowed the thickness of the Kalahari sands to be quantified, far shallower than anticipated, increasing the exploration prospectivity of the region and a geological map of the area, based on these results, has been created in an area with very little data coverage and no outcrop.