New insights into the Central Gawler Gold Province, SA

摘要

The Gawler Craton in South Australia hosts significant gold resources with over 2,800t (98Moz) of defined gold resources, the majority of which are attributable to (iron oxide) copper-gold systems associated with the ca. 1590Ma Hiltaba mineralising event and concentrated along the Eastern margin of the Gawler Craton. Earlier workers recognised a separate region within the Gawler Craton characterised by gold-only mineralisation known as the Central Gawler Gold Province (CGGP), although the geological parameters that influence the formation of the occurrences within the CGGP have long been equivocal. Recent investigations have sought to examine and understand the key controls around the formation of the gold-only systems and refine the definition of this Province.A specific focus of this research is considering whether a single magmatic or orogenic source, or a combination of sources is a more likely explanation for these gold occurrences. Sulphur isotope evidence and sediments of a low metamorphic grade support an orogenic origin for the Tarcoola deposit, whilst geochronology investigations from the Barns deposit demonstrate upper amphibolite facies metamorphism at ca. 1690Ma, predating gold mineralisation by ~100Myr, suggesting these rocks are unlikely to be able to generate significant fluid by metamorphic devolatilisation reactions. The close spatial relationship of mafic-intermediate dykes to mineralisation is also being investigated with stable and radiogenic isotopic data suggesting that the dykes are integral to mineralisation but that the signature and, to some extent, style of mineralisation varies as a result of the host rock to the dykes and mineralisation. An improved understanding of the CGGP is expected to contribute towards improved exploration targeting, which in conjunction with refined and improved targeting techniques, will lead to a new generation of gold discoveries.