KING GEORGE: Measured and modelled AGG response over an IOCG terrane

Abstract

King George is a high priority magnetic anomaly that was identified within regional aeromagnetic data. The anomaly is located in 20-30m of water in the Spencer Gulf, South Australia, adjacent to the Moonta-Wallaroo mining field. Regional geology indicates that this area is highly prospective for Iron Oxide Copper-Gold (IOCG) style deposits. IOCG deposits are expected to have a high gravity signature with possible association of magnetic anomalism, the latter being dependent on magnetite content. In March 2000, the Falcon airborne gravity gradiometer (AGG) system was flown over the King George anomaly, previously inaccessible to conventional gravity measurement techniques. The survey showed a 7 mGal gravity anomaly coincident with the 10,000nT magnetic anomaly, making the anomaly to a high-priority drill target. Modelling of the airborne gravity and magnetic data indicated that two closely spaced bodies 200m below the surface produced the observed anomaly. Vertical gravity gD was used during the modelling exercise. The Falcon AGG system measures the quantities GNE and GUV from which vertical gravity gradient GDD and vertical gravity gD are derived. To verify the gravity model, the GNE and GUV responses were also computed and compared with actual quantities measured by the Falcon AGG system. A good match between the measured and the modelled components was obtained.