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Deposit Synonyms
Daveys Lode; Harveys Lode; Main Lode; Milnes Lode; North Mairs Lode; North Youngs Lode; South Lode
Mineral District
Moonta - Wallaroo
Deposit Summary
Cu-Au-Ag mineralisation in series of shear-hosted, en echelon lodes in host deformed metavolcanic, and metasediment of the Doora Schist. Production from 1861-1923 ~4.2Mt. Remaining mine resources ~520,000t @ 3.8%Cu.
Deposit Description
WALLAROO, Cu-Au mineralisation in host sequence of intensely deformed metavolcanic, and metasediment rock of the Doora Schist. Included mica schist, amphibolitic schist, quartzite, and gneiss and iron formation. The main ore bodies of chalcopyrite, pyrite, and pyrrhotite with a trace of molybdenite, galena, and sphalerite were confined to EW- to ESE-trending shears and comprised stringer, quartz-vein, and laminated ores in a quartz, biotite, feldspar and tourmaline gangue. Mineralisation age 1577 +/-6Ma (molybdenite, Re-Os).
The ore bodies were offset in an en echelon pattern by NE-trending faults and shears. At their extremities the NW-SE-trending ore shoots tended to fray out, finally losing their identity. Wallaroo Main Lode had the form of stacked lodes arranged en echelon over a distance of ~1km from Wallaroo main Lode in the south , then North Young Lode, Milne Lode, and North Mair and Harvey Lode in the north. Minor mineralisation occurred in sets of axial-planar NNE-trending lodes.
Production figures for the Wallaroo Mine area were estimated at 4.2 million tonnes (Mt) for the period 1861-1923. Grade figures were not available, but dressed ore averaged ~10% Cu. Gold and silver were recovered. For the combined Moonta-Wallaroo mining areas it was estimated that production was 3000 kg of gold, and 5000 kg of silver at grades of 0.34 g/t Au, and 0.56 g/t Ag. In 1923, at the cessation of mining remaining resources in the deeper parts of the mine were estimated at 520,000 tonne at 3.8% Cu.
Cameron (2014), examining samples of ore from Moonta and Wallaroo show an abundance of pyrrhotite, with late superposed hematite inferring a shift from reducing to oxidising conditions. Replacement textures of chalcopyrite replacing bornite, and vice versa suggest multiple episodes of ore crystallisation.
Discovery Year
? 1861
Commodities
Copper, Gold, Silver
Ore Minerals
Argentite, Atacamite, Azurite, Bornite, Chalcocite, Chalcopyrite, Copper, Covellite, Cuprite, Ferberite, Galena, Gold, Malachite, Molybdenite, Smaltite, Sphalerite, Tenorite
Gangue Minerals
Amphibole, Apatite, Biotite, Calcite, Chlorite, Clay mineral, Dolomite, Feldspar, Fluorite, Hematite, Kaolinite, Muscovite, Pyrite, Pyrrhotite, Quartz, Rhodochrosite, Scapolite, Sericite, Siderite, Tourmaline
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