A Study of the Subsurface Model of Base Metal Mineralization using Complex Geophysical Exploration in Wadi El Khadra Prospect, Kingdom of Saudi Arabia

Abstract

Wadi El Khadra prospect comprises numerous gossan outcrops in metamorphic aureole which lies along the contact between a gabbro intrusion and the metamorphic country rocks. The first phase of a recent exploration program, in this area, included geological, geochemical and self potential (SP) geophysical investigations. The results of this phase revealed that the geochemical copper and nickel anomalies coincide with the SP anomalies. A number of drill hole sites were recommended from the interpretation of the SP response to test the mineralization in the subsurface.

The present paper deals with the late phase of the geophysical exploration which included Slingram electromagnetic (EM) and frequency domain induced polarization (IP) surveys. Compared with the SP method, these methods allow deeper penetration and provide additional useful information about the mineralization in the subsurface. Data reduction and compilation of both EM and IP surveys have been carried out using advanced computer software. The final output of these surveys is presented as reduced profiles and maps.

The integrative interpretation of the geophysical response of the different geophysical methods revealed more precise information about the subsurface configuration and mineral distribution in the prospect area. Strong geophysical anomalies were observed in the southern part of the gossan outcrops, while the northern part is associated with relatively weaker response. The qualitative and quantitative interpretations of the EM and IP anomalies succeeded in approximating the subsurface model of the mineralized body and distinguished the interesting parts which yield the best mineral potential. The filtered IP maps were successfuly used to locate more precise sites for the subsequent exploration drilling. The new drill hole sites were different from those suggested using the SP method.