Geophysics and the discovery of the Cadia gold-copper system

Abstract

The Cadia Gold Copper system in Central West NSW is a world-class porphyry gold copper system, where geophysics has helped to discover or define some of the resources. Initial drilling at Cadia Hill employed ground magnetic data to help optimise drillhole direction. A ground magnetic target was drilled at Cadia East, and showed increasing copper grades with depth. Follow up drilling discovered the Cadia East mineralisation under Silurian sedimentary cover. Ground magnetic and 200m dipole-dipole IP data led indirectly to the discovery of the Ridgeway mineralisation under Tertiary basalt cover, by detecting the magnetite and pyrite halo above the mineralisation. The IP drillhole intersected anomalous gold and copper. Deeper follow up drilling intersected the Ridgeway orebody. Other data acquired across Cadia include heli-magnetics / radiometrics, gravity, downhole EM at Ridgeway, and physical property measurements. Overall, magnetics and IP have been the most successful methods used to date.