Magnetic Susceptibility of Edmund Basin, Capricorn Orogen, WA

Abstract

Magnetic anomalies appear to be related to base metal prospects in the Mesoproterozoic Edmund Basin of the Western Australian Capricorn Orogen, one of them being the cause of finding the Abra Pb-Cu-Zn deposit. Our results from Edmund and Collier lithostratigraphic units show that magnetic susceptibility of the older dolerites is less than that of the younger, and that weathering appears to decrease the magnetic susceptibility response at outcrops. Sedimentary rocks and Moorarie Supersuite monzogranite have lower magnetic susceptibility than the mafic intrusive rocks. Hydrothermal quartz and diorite related to Moorarie Supersuite have high susceptibility and either of these or both may relate to magnetic highs at locations of outcropping or nearly outcropping basement rocks. Hydrothermal alteration seems linked to higher susceptibilities, but additional sampling from fresh unaltered rock and hydrothermal alteration as well as petrographic studies to define the magnetic accessory minerals in Edmund and Collier Basin lithostratigraphic units are required to understand the link between unit mineralogy and magnetic properties.