GOLD: Relationship between magnetic anomalism and epigenetic gold mineralisation in the Victory-Defiance area, Western Australia

Abstract

The relationship between gold mineralisation, genetically related mineral assemblages, magnetic susceptibility and features observable in ground and airborne magnetic surveying is established at three gold mines in the Victory-Defiance gold camp at Kambalda, Western Australia. The gold mines are Orion, North Orchin and Revenge. There are significant magnetite-stable alteration haloes enveloping the gold lodes comprising these deposits. The magnetite-stable alteration is peripheral to gold lodes in differentiated dolerites, metabasalts and metasedimentary rocks which have undergone lower to mid-greenschist facies metamorphism. The magnetite alteration is partly coincident with the well-documented chlorite and biotite alteration zones. The magnetic susceptibilities of the magnetite-stable alteration assemblages range to 100 ´ 10-3 SI units. It is noted that the magnetic properties of the Kapai Slate vary considerably on a regional scale but appear to be consistently high (up to 400 ´ 10-3 SI units) within the Victory-Defiance gold camp. Magnetic maxima are coincident with all three gold deposits. The amplitude of the maxima observed in low-level aeromagnetic surveys are 30, 300 and 400 nT for Orion, North Orchin and Revenge, respectively.