Structural mapping under cover with airborne EM

Abstract

The drive to explore under cover necessitates methods of geological or geochemical mapping that can ?see through? the masking cover rocks. Magnetic data are routinely collected for this type of structural mapping in various terranes. In Mali, magnetic data have been of very limited use to Resolute Mining?s mineral exploration programs - magnetically featureless cover rocks hide almost all structural expression in the basement. Airborne EM has proven invaluable in tracing lithological contacts, subtle stratigraphic horizons, and intrusive bodies through conductive weathering up to 100m deep. Helicopter time domain systems with high transmitter moments penetrate deep enough to escape contamination by surficial conductivity features such as drainage patterns. The results under basin cover in Mali are particularly impressive in their ability to provide a clean picture of basement geological structure.