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

The Eastern Gawler Craton IOCG Province, South Australia, hosts a number of IOCG deposits associated with Hiltaba Suite magmatism under deep cover. Exploration methods increasingly rely upon geological models derived from potential field data to define the crystalline basement drill targets. Coincident gravity - magnetic anomalies have been successfully applied for predicting iron oxide alteration, such as targeting the Carrapateena IOCG deposit. This has lead to widespread modelling of aeromagnetic and gravity data based on iron oxide properties. The Geological Survey of South Australia is attempting to generate 3D inversions of the Emmie Bluff and Punt Hill regions. Over 17,000 magnetic susceptibility and specific gravity measurements have been captured from drill core samples. Geochemical and mineral spectrometry data have used to characterise a skarn style that cannot be modelled using the iron oxide distribution.

Gravity anomalies associated with the Emmie Bluff and Punt Hill IOCG prospects have with similar character. Examples of the petrophysical characteristics of the different styles of IOCG deposits are described. Petrophysical data from drill holes SAE 6 and PRL 23 / SAR 9 demonstrate that similar density values can be gained from different alteration mineralogy. Emmie Bluff deposit (drill hole SAE 6) density anomalies relate to iron oxides alteration and in the Punt Hill region (drill hole PRL 23 / SAR 9) high density values are a due to skarn mineralogy (garnet-pyroxene-amphibole).