Abstract

An analysis of temperature data from drill holes on the Stuart Shelf of South Australia demonstrates a major thermal anomaly associated with the Olympic Dam copper-uranium-gold deposit. The average heat flow on the Stuart Shelf (seven locations, excluding Olympic Dam) is 73 mW/m 2 , but an additional heat flow of approximately 45 mW/m 2 , is present in the sediments overlying the orebody. Although some of the anomalous heat flow appears to be generated in the mid-Proterozoic basement at depths greater than 1 km, uranium assays indicate that approximately 30 mW/m 2 can be attributed to concentrations defining the orebody. Major anomalies in heat flow can be readily detected in the flat-lying cover of Cambrian and late Proterozoic sediments. The Tregolana shale within this sequence is a widespread homogeneous unit, typically 100-200 m thick. It is easily identified on temperature logs by its high thermal gradient relative to other sections in the hole. The heat flow anomaly at Olympic Dam is clearly distinguished by measuring thermal gradients within the Tregolana shale; gradients in the Tregolana shale at Olympic Dam are close to 83 degrees C/km, with a standard deviation (SD) of 6 degrees C/km, compared to 51 degrees C/km (SD = 7 degrees C/km) elsewhere on the Stuart Shelf.

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