Deposit Synonyms

Mineral District

Deposit Summary

drilling penetrated Cu mineralisation with anomalous Zn-Pb-Ag-Co in basal Tapley Hill formation at 160m depth over an area 15km long by 3km EW.

Deposit Description

MYALL CREEK, available geological, geophysical and drillhole data indicate a geological setting of a graben infilled with Mesoproterozoic Pandurra Formation, basal Adelaidean Beda Volcanics, and overlain by Adelaidean Tapley Hill Formation. To the west (Roopena) and the east (Cultana) shallow basement ridges of Mesoproterozoic Gawler Range Volcanics and Hiltaba Granite were evident in outcrop and from the magnetics. The prospect was identified in 1975 during exploration for Zambian Copperbelt-type mineralisation on the Stuart Shelf. Drillholes intersected copper sulphides, with lesser zinc and lead, and accessory silver and cobalt, over an area extending 15 km NS by 3 km EW at a variable depth averaging about 160m. Mineralisation occurs at the base of the Tapley Hill Formation in a thin white sandstone, and in an overlying silt-dolo-laminite facies. Deposition of the basal part of the Tapley Hill Formation was influenced by relief related to N- to NW-trending faults. Minor copper sulphide mineralisation occurs in underlying Beda Volcanics. The deposit shows metal and mineral zoning both vertically and laterally. Apart from pyrite, the sulphide metals are of epigenetic origin. The ore minerals occur as both disseminations, and as small, cross-cutting and bedding-parallel veinlets. The main ore minerals are chalcopyrite, chalcocite and bornite, with rare tennantite. Sphalerite, galena and pyrite aree also present. Pyrite and bornite tend to occur in thin, carbonaceous silty laminae. The basal sandstone shows much alteration of plagioclase to clay. The main copper mineral in the sandstone host is tennantite occurring as disseminations and in complex intergrowths with chalcocite, bornite, sphalerite and galena. The deposit demonstrates a central zone of 3 km2 of higher Cu grades (up to 2.2%). The genesis of the mineralisation is proposed as a secondary migration of mineralised fluids through permeable strata of the Tapley Hill Formation.

Discovery Year

? 1975

Commodities

Copper, Lead, Zinc, Silver

Ore Minerals

Bornite, Chalcocite, Chalcopyrite, Galena, Sphalerite, Tennantite

Gangue Minerals

Pyrite

? Stuart Shelf

regional graben infilled with Mesoproterozoic Pandurra Formation to Adelaidean volcanics and sediment, with epigenetic mineralisation occurring in permeable strata of the basal Tapley Hill Formation.