The application of airborne geophysics in the exploration for iron ore in the Zouerate area of Mauritania

Abstract

An airborne time domain electromagnetic and magnetic survey (Geotech VTEM system; VTEM is a helicopter-borne Time Domain Electromagnetic (TDEM) system with concentric loop transmitter receiver geometry.) was flown over the Kedia mountain and Mhaoudat Intrusive in Mauritania. Hematite has been mined in both these areas for many years. The objectives of this survey were to determine if additional ore bodies existed below old mined areas and to find and delineate possible new ore bodies. A detailed structural interpretation, using the magnetic and EM data, was done with the assumption that major faults could be a controlling factor on the occurrence of iron ore. Decay curve analysis was done of the VTEM data as a fast, first pass delineation of conductive areas. Good correlation with existing mines was found. CDI?s were consequently calculated for all flight lines. These were used to calculate conductivity contour maps at various depth intervals below the surface. Conductive areas were correlated with the magnetic data as well as the known geology. In several areas known iron ore was associated with the edges of observed anomalies. These anomalies continued at depth and distance, indicating possible extensions of the ore. Further anomalies occurred in a sand covered area south of Mhaoudat, leading to the possibility of new iron ore deposits.