Mount Gunson Copper mines, Pernatty Lagoon, South Australia, Australiai

Regional Level Types
Mount Gunson Copper mines	Group of Mines
Pernatty Lagoon	Lagoon
South Australia	State
Australia	Country

The district is named after Mount Gunson, a small but prominent hill with a height of 232m near the Mount Gunson Mines, and Pernatty Lagoon - a nearby salt lake. It hosts a number of important Cu-Ag-Co deposits, including the Cattle Grid; Main Open Cut; West Lagoon; East Lagoon; MG 14 and Windabout deposits, plus Bornite Workings; Guyah; Pernatty Lagoon; ML 4247; A & MJ Musolino Pty Ltd; Brennans Claim; EML 6192; ML 3717; ML 3718; ML 3719; ML 3720; ML 3721; ML 5598; some of these latter leases probably relate to the above deposits. None are currently operational (2013).

Mount Gunson is located on flat-lying Late Precambrian platform sediments overlaying the Gawler Craton horst/graben crystalline basement within the Olympic Dam Copper-Gold Province, a generally North trending feature which hosts Olympic Dam and a number of other significant copper-gold mines. Copper and gold deposits occur in iron oxide rich deposits in the basement, and copper-silver-cobalt in overlying brecciated sediments.

The sediments host gently dipping lenticular orebodies of copper sulphide mineralisation with plan dimensions measured in kilometers or fractions thereof, and thicknesses varying from about 3-10m. Their depths vary from 10s of m to up to 400m deep. The orebodies display a marked ore gradation highest in the upper section. This upper zone can include a brecciated carbonate-rich sandstone within a carbonate-rich mudstone host. As of 2013, two of the shallower deposits (the MG14 and Windabout) have been exploited by open pit methods.

Sandstone-hosted orebodies are mostly associated with the Pandurra Formation, a 1km thick fluviatile sandstone unit which contains breccias in its base and top. Shale-hosted orebodies within the overlying Tapley Hill Formation are much finer grained and not necessarily breccia hosted. Minerals include chalcocite, bornite, chalcopyrite, covellite, and carrolite.More regionally, atacamite has been noted at the surface and has been ascribed to the salinated surface environment.

Multiple mining operations have been established in many of the deposits since as early as the 1875, starting with the Main Open Cut and West Lagoon, but with the Cattlegrid deposit, found in 1971, being the largest. Some deposits have been sporadically re-mined based on bulk mining from open cuts with lower ore grades, with additional ore discoveries being found by continued drilling in the area up till the present day. Previously owned by Mount Gunson Mines Pty, later by Salisbury Resources Ltd, now by Gunson Resources (2013). Salisbury’s Main Exploration Target was a 11-12 million tonnes @ 1-1.5 % copper and 5-10 g/t silver with additional cobalt credits from the prospective zone of the un-mined Cattle Grid Breccia north of the existing pit.

Crystalline gypsum is common within Quaternary sand spreads.

For the copper sulphides, flotation recovery is poor at marketable grade but leaching of low-grade concentrates has shown some promise. For that reason, the now-defunct Cattlegrid and Main Open Cut pits use in-pit heap leaching and cementation. In addition, recovery of metallic copper, cobalt and silver at the mine site is being explored via a solvent extraction-electrowin process.

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