The Use of VTEM Data in Geological Mapping and Mineral Exploration in North-eastern Namibia.

In June 2008 a 3310 line-km airborne geophysical survey was flown in north-eastern Namibia for the Geological Survey of Namibia. Time domain electromagnetic data (dB/dt and B-field) as well as magnetic data were acquired with the VTEM system. The survey area is covered with sand and no other detailed information on the sub-surface geology is available. The objectives of the survey were to delineate sub-surface geological units and trends, and to identify possible exploration targets. The TDEM data were processed to obtain three-dimensional conductivity-depth information, decay constant maps and discrete anomaly picks from both the B-field and dB/dt data sets. Together with the magnetic total field data and its derived products (analytical signal, vertical and horizontal derivatives), these were used to delineate geological structures and classify geological units based on their regional setting and physical properties. In addition, targets with exploration potential were identified. The data and some interpretation results are presented in this paper, illustrating the value added to regional mapping and greenfields exploration with airborne TDEM surveys.