Alteration and Mineralisation in the Moonta-Wallaroo Cu-Au Mining Field Region, Olympic Domain, South Australia
by
Colin Conor, Geological Survey Branch, Primary Industries and Resources South Australia, Adelaide, South Australia Oliver Raymond, Minerals Division, Geoscience Australia, Canberra, ACT., Australia, Tim Baker, Geological Survey Branch, Primary Industries and Resources South Australia, Adelaide, South Australia, Graham Teale, Teale and Associates, Pty Ltd, Prospect, South Australia, Patrick Say, Rex Minerals Ltd., Ballarat West, Victoria, Australia, and Geoff Lowe, White Rock Minerals Ltd, Ballarat, Victoria, Australia.
in Porter, T.M. (Ed), 2010 - Hydrothermal Iron Oxide Copper-Gold and Related Deposits: A Global Perspective, Advances in the Understanding of IOCG Deposits; PGC Publishing, Adelaide. v. 3, pp. 147-170.
ABSTRACT
The Olympic Copper-Gold Province of the eastern Gawler Craton of South Australia, in hosting the Olympic Dam, Prominent Hill, Carrapateena and Moonta-Wallaroo deposits, has the greatest known iron-oxide, copper, gold and uranium (IOCGU) metal endowment of any geological province on Earth. The historic Moonta-Wallaroo copper-gold mining field is within the Moonta sub-domain and is hosted by the ~1750 Ma Wallaroo Group that preserves some evidence of evaporitic sedimentation, similar to other major iron oxide-copper-gold (IOCG) provinces in Australia and North America. Observations in the Moonta-Wallaroo district indicate that mineralisation was broadly associated with intense metasomatic alteration, intrusion of granites and gabbros of the Hiltaba Suite, moderate grade metamorphism and intensely partitioned deformation. The driving force of this extensive ~1600 to 1500 Ma hydrothermal, magmatic and tectonic event was a major thermal pulse, the cause of which remains under debate. The vein-style mineralisation in the Moonta-Wallaroo district developed in ground prepared by ductile shearing. Widespread sub-economic copper mineralisation in the region is associated with intense regional magnetite-bearing skarn-like alteration of the Cloncurry type, with oxidation and hematite replacement of early magnetite. Targeting of structurally-controlled demagnetised zones and the oxidised margins of magnetic anomalies has been applied successfully in the northern Olympic Copper-Gold Province (e.g. Prominent Hill) and is also applicable to the Moonta-Wallaroo region. The recently discovered copper-gold mineralisation at the Hillside copper-gold deposit demonstrates the continued prospectivity of this southern portion of the Olympic Copper-Gold Province.
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