Discovering Deeper Porphyry Ore Bodies - is there a role for geophysics?

Abstract

The anticipated almost doubling of world mine Cu production by 2030 will require a substantially increased output from existing porphyry Cu mines, along with production from as yet undeveloped mines and the discovery of new porphyry ore bodies. Assisting the potential for increased output from existing and new mines, and partly in response to declining ore grade, mass (large-scale) mining of porphyry Cu ore bodies is undergoing a major transformation, foreshadowing a significant increase in the size of some existing and future mining operations. The discovery histories of two of the four Cadia, porphyry Au-Cu ore bodies in New South Wales, Australia offer insights into discovering deeper porphyry ore bodies. Induced polarisation geophysics (IP) contributed importantly to one of these discoveries (Ridgeway) by identifying the overlying 'sulphur' halo to the ore body. It is proposed that IP, and possibly other geophysical methods, can play a greater role in discovering deeply-located porphyry ore bodies, when used as part of an 'ore-system' approach to discovery; particularly if the methods can be modified so as to 'see' much deeper than at present and used to identify a porphyry 'sulphur' halo, starting at a depth below surface of up to 1,000 m.