Geophysical exploration for graphite at Uley, South Australia

Abstract

Graphite mineralisation occurs over a significant area in the south and east of the Eyre Peninsula, South Australia, with the majority of production coming from the Uley Mine, near Port Lincoln. Here, flake graphite mineralisation occurs in a complexly folded and faulted succession of schists and gneisses of Palaeoproterozoic age. The earliest geophysical surveys at Uley took place in the 1930s. Further surveys were carried out in the 1950s. These surveys showed the mineralisation is conductive and when shallow gives rise to negative SP anomalies and resistivity lows. Frequency-domain EM surveys also successfully detected shallow mineralisation. Physical property measurements have shown the graphite ore to be significantly more conductive than the host rocks, but magnetic susceptibilities are uniformly low in the mineralised environment. Modern IP/resistivity surveys mapped a chargeable and conductive source coincident with known mineralisation. A more extensive SIROTEM survey successfully mapped several conductive zones in the mine area. These responses are consistent with the expected geometry of the mineralisation. Subsequent drilling showed there was excellent agreement between conductive areas in the subsurface and graphite mineralisation.