Application of transient airborne electromagnetic and ground resistivity methods to geological mapping in tropical terrains

• Main Author: Barongo, Justus Obiko
• Format: Others
• Language: en
• Published: McGill University 1989
• Subjects: Geophysics.
• Online Access: http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=75983

The feasibility of using time-domain airborne electromagnetic and ground resistivity methods in geological mapping in tropical terrains is investigated. The investigation is based upon evaluation of the linear inverse theory in the determination of physical parameters of the weathered layer necessary for interpretation of underlying lithology. === Inversion of ground resistivity sounding data from the greenstone belt in western Kenya yields conductivities and thicknesses that are consistent with geology. A similar inversion of modelled time-domain airborne electromagnetic data shows that conductivity, thickness and depth to the top of the conductive weathered layer can be uniquely determined if its response does not suffer the thin sheet response problem. The results further show that this problem can be quite common in tropical regions since much of the weathered layer has low conductivity and thickness and, consequently, the response is weak. In this situation, conductivity and thickness are correlated and conductivity-thickness product is better determined than these two parameters independently. === By virtue of the weak time-domain AEM response of the weathered layer, much of the response remains buried in noise. This situation introduces further complications for an inverse problem that is highly non-linear. A method for reducing some of this noise before carrying out the inversion is presented.