|
Deposit Synonyms
Mineral District
Deposit Summary
IOCG-type mineralisation beneath ~800m cove. Barren Donington Suite granite, then 15m @ 1.23% Cu in strongly hematite altered rock, underlain across a gradational boundary, by 104m @ 0.27% Cu in shale of the Walleroo Group.
Deposit Description
EMMIE BLUFF NE, the north-eastern of 2 near-coincident magnetic and gravity features on a 11km long NE-trending magnetic feature. Drill tested in diamond holes in 1989 , with SAE6 penetrating a zone of mineralisation, cutting the basal contact between the Pandurra Formation and the underlying basement and intersecting 75 m of foliated Donington Suite granite, then 15m @ 1.23% Cu in strongly hematite altered rock, underlain across a gradational boundary, by 104m @ 0.27% Cu in shale that was partially to wholly replaced by magnetite and associated pyrite. The holes identified a mineralised zone ~150 m thick and ~3 km in diameter that clearly overprints relics of an earlier higher temperature magnetite alteration stage.
Cu mineralisation is as veins or as replacement of host rock. It is dominantly associated with a low-T assemblage of hem-qz-chl-py that overprints the magnetite stage. Ore minerals included chalcopyrite, bornite and minor covellite. Highest grade intervals contain up to 2.8 wt.% Cu and up to 0.6 g/t Au over intervals up to 10m, often enclosing thinner zones of >4 wt.% Cu and >1 g/t Au.
A set of reverse/thrust faults that produced stratigraphic repetitions in the upper Wallaroo Group metasiltstone and the structural emplacement of the Donington Suite granitoid appears to have channelled the mineralising fluids in the NE mineralised zone. The relation between these structures and the regional-scale fault that has localised magnetite deposition is unclear. Enhanced permeability caused by brittle fracturing associated with the faults was also a major influence on the localisation of mineralisation.
There is a crude downward alteration zonation, from upper breccia and cataclasite zones associated with the faulted contact between Donington Suite and Wallaroo Group, where intense hematite-chlorite-quartz (or hematite-sericite-quartz, depending on the protolith lithology) alteration is accompanied by chalcopyrite-pyrite-bornite-covellite, to less brecciated relic magnetite-chlorite-pyrite-altered zones lower in the mineralised zone. Pervasive sericite alteration and late-stage fluorite veins represent the final phases of the hydrothermal activity. Main reference to body of text is Porter, T.M., Hydrothermal Iron Oxide Copper-Gold and Related Deposits: A Global Perspective PGC Publishing Adelaide, 2010.
Discovery Year
? 1989
Commodities
Copper, Gold
Ore Minerals
Bornite, Chalcopyrite, Covellite
Gangue Minerals
Chlorite, Hematite, Magnetite, Pyrite, Quartz
|