Porphyry-type copper deposits, eastern Victoria

Abstract

"Most occurrences of porphyry-type copper mineralisation in Victoria are within the Lachlan Fold Belt in eastern Victoria. Chalcopyrite, chalcocite and pyrite are the main ore minerals. Molybdenum is sometimes present. The mineralised intrusions include the Bete Belong Suite (Double Bull Creek, Sunday Creek, Stringer Knob and Mount Buck prospects), the Kaerwut Trondhjemite (Dogwood Prospect) and the Nunniong Granite (Tiger Creek Prospect). These mineralised, Silurian-Devonian intrusions are either side of the Buchan Rift. Most of the mineralised intrusions are intermediate in composition and tend to be magnetic. The Bete Belong Suite granites lie east of the Buchan Rift and form a series of magnetic ''highs''. The Kaerwut Trondhjemite is a much smaller intrusion and is associated with a more subdued magnetic response. The Nunniong Granite is less easily recognised. In most cases a magnetic survey would find the host intrusion but not the mineralisation. The induced polarization method is successful in locating the sulphides. However, most induced polarization anomalies are probably caused by pyrite, which is present in larger concentrations and is more widespread than the economic sulphides. Supergene chalcocite also contributes to induced polarization anomalies. The resolution of the gravity data are too low resolution to permit the correlation of gravity signatures with any of the intrusions. All known copper porphyry prospects in Victoria are uneconomic."