High-resolution mapping using a sub-audio magnetic survey at the Comet Gold Mine,Western Australia

Abstract

The Comet Gold Mine in the Murchison mineral field lies within the Yilgarn Craton of Western Australia. Gold mineralization in this area is associated with a series of north-northeasterly trending structures, and has a long exploration history with some previous geophysical information. Other exploration information, such as geology and drill hole data, are integrated with the geophysical results to study the geophysical responses and generate a geophysical interpretation map. The response from the sub-audio magnetic (SAM) survey was investigated over an area of 13 sq km. The SAM survey was completed using a transmitter current of 5 - 8 Amp with a 50% duty cycle at 4 Hz frequency, which was considered a good instrumental setting for the Comet area. SAM anomalies were compared to results obtained from other geophysical methods and then integrated with geological data to generate a geophysical interpretation map at a 1 : 5000 scale. The new interpretation of geological units and structures at the Comet area should provide a better understanding of the geological and structural setting for mineralization in the Comet area. Our results show that the Comet Fault represents a faulted limb of the Comet fold structure that has both limbs dipping to the southeast and a plunge to the northeast. Magnetic anomalies associated with sedimentary iron formation (SIF) are considered to be well correlated with some gold bearing horizons and the location of the Comet Fault, which has become more siliceous and has been altered by sulphide minerals and magnetite minerals.