Examples of DHEM in nickel sulphide exploration within the Kambalda District, Western Australia

Abstract

Geophysical and geological interpretation of Drillhole Electromagnetic data (DHEM) from exploration projects within the Kambalda District, Norseman-Wiluna Belt, demonstrates the usefulness of the technique in the exploration program and for the direct detection of Archaean massive nickel sulphide accumulations. DHEM surveys can assist exploration by generating drill targets based upon interpretation of "offhole conductor" responses. Furthermore, under favourable geological conditions, DHEM is able to "sterilise" a prospective contact for the occurrence of massive sulphides for distances of 50?80 metres around a drillhole, depending on the size of conductive targets. DHEM surveys therefore increase the effectiveness of drillholes and reduce the total number of drilling-metres required to fully evaluate a prospect. The axial-component DHEM profiles from nickel prospects illustrate a variety of possible responses relating to the position and the conductive properties of the source of the anomalies. Solitary or multiple inhole responses are recorded from intersected nickel sulphide lenses that are indicative of conductor size, geometry and conductivity. Offhole response(s) generate prospective targets and the recorded response is used as a vector to direct future drilling at the prospect.