Magnetic petrophysics in the Stawell Gold Field: relating aeromagnetic anomalies to mineralising fluid flow

Abstract

Aeromagnetic anomalies at the Kewell Prospect in the Stawell gold field are characterised by negative lobes on the flanks of the Kewell structure, which require a source with reversed remanence. Direct measurement of remanence in Kewell samples was not possible, but hysteresis analysis of samples from Kewell and Stawell allow the pyrrhotite-bearing lithologies responsible for the magnetic anomalies to be divided into two populations. Population A spatially corresponds to zones of modelled high flow rates of mineralising fluids at Kewell, suggesting that the flow environment may directly influence magnetic properties, and through this influence, control the polarity of remanence. High fluid flow and associated gold endowment at Kewell appear to be associated with reversed remanence, and are sign- posted therefore by negative magnetic anomalies.