The geophysical signature of the Batman Gold Deposit, Mt Todd Project, NT

Abstract

The Batman gold deposit at the Mt Todd Project is situated within Early Proterozoic metasediments of the Pine Creek Geosyncline, Northern Territory. It was discovered by the Mt Todd Joint Venture (Billiton Australia and Zapopan) in 1988, following regional geochemical reconnaissance surveys. The gold mineralisation is contained in a sheeted and stockwork quartz-sulphide vein system hosted by massive greywackes and siltstones of the Burrell Creek Formation. Although the sulphides (mainly pyrite and pyrrhotite) are less than 5% in volume, the network of quartz-sulphide veins means that the deposit is an excellent conductor and this results in very strong EM and IP responses against a resistive background. The total volume of pyrrhotite also leads to a moderate (140 nT) aeromagnetic anomaly which is distinctive and isolated against a generally low regional magnetic field. Although any substantial amount of known gold mineralisation in the area has a geophysical response, it also appears that some anomalies (such as to the north of the Batman deposit) reflect sulphide mineralisation which has little or no associated gold. Thus geophysics proves to be a useful, but not totally conclusive, tool for detecting gold mineralisation in this part of the Pine Creek Geosyncline.