Petrophysical constraints for inversion models of the Eastern Gawler Craton IOCG Province

Abstract

The Eastern Gawler Craton IOCG province , South Australia, hosts a variety of deposits associated with Hiltaba Suite magmatism. Adjacent to the southern margin of the Carrapateena haematite breccia deposit lies the Emmie Bluff and Punt Hill regions which host skarn mineralisation in the palaeoproterozoic Wallaroo Group beneath 1 km of cover. Within those two smaller regions are two distinct iron and copper skarn styles of mineralisation. Exploration methods under deep cover rely upon geophysical signatures from airborne and ground surveys to select drill targets, define the cover sequences and basement. This process can be improved using petrophysical properties to constrain 3D inversion models. A wide range of petrophysical properties have been collected over the area to relate the known geology with geophysical surveys. Magnetic susceptibility and specific gravityhave been captured to characterise altered units. The Emmie Bluff and Punt Hill regions has been the subject of 3D inversion modelling projects undertaken by the Geological Survey of South Australia which required geological constraints due the distinct styles of alteration and mineralisation. Within the Wallaroo Group, the both gravity and magnetic sources within Emmie Bluff are controlled by iron oxide alteration, whereas in the neighbouring Punt Hill region the density characteristics are dominated by skarn alteration and the magnetic source appears independent of the altered stratigraphy. This work presents characterisation of mineralisaed stratigraphy used for 3D inversions of the region. The data is available for download from the SARIG website.