Black Swan Mine (Silver Swan; Cygnet), Broad Arrow, Kalgoorlie-Boulder Shire, Western Australia, Australia

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Ni deposit, located 53 km north north east of Kalgoorlie.


This small nickel deposit was discovered in the late 1960's during the nickel boom. The Silver Swan underground mine started in 1996 and the Black Swan open pit in 2004. Both were placed on care and maintenance in 2009. The mine was originally owned by MPI Mines Ltd, then was acquired by Lionore in 2004, in turn this company was taken over by Norilsk in 2009.

Black Swan is a disseminated deposit, further underground the Silver Swan is massive sulphide ore, and the Cygnet deposit is high grade disseminated ores lying underneth the Black Swan ore. All three are located in the Black Swan Komatiite, located in the upper greenschist to lower amphibolite facies of the metamorphosed felsic metasedimentary dominated Gindalbie Formation. The Black Swan Komatiite dips steeply north-east, 150-600 metres thick, and is 3 kilometres long. A large amount of the komatiite has been altered to carbonate-quartz-talc-sericite, and in the less altered areas is antigorite-carbonate-talc-chrysotile serpentinite.

The Black Swan deposit is low grade disseminated nickel accumulate, 400 metres south-east of Silver Swan, and 50 metres above the base of the Black Swan Komatiite. It is an elongate body, 350 metres long, with a central core of pyrite,millerite,violarite, surrounded by discrete smaller mineralised zones. Thickness and nickel grades decrease with depth. The disseminated sulphide is composed of up to 2mm interstitial olivine pseudomorphs, and also contains a rare droplet style up to 10mm across. Both are predominantly pyrite and lesser millerite,magnetite and minor violarite,chalcopyrite.

The Silver Swan deposit is a dicrete, steeply plunging high grade massive sulphide shoot of pyrrhotite, pentlandite, pyrite, chalcopyrite, magnetite and ferrochromite. Mineralisation occurs on the footwall, 190-740 metres below the surface, up to 20 metres thick, 75 metres long, and dips at 45-75 degrees north-east. There is upper and lower lenses seperated by a narrow neck. There is no sulphide mineralisation in the footwall or hanging wall. The massive sulphide is coarse grained with no banding or layering, although stringers and sub-parrallel lenses exists. The ore contains pyrrhotite and pentlandite with minor violarite, chalcopyrite, pyrite and gersdoffite.

Cygnet is a coherent uniform lens of disseminated pyrite, millerite, vaesite, 5-10 metres above the base of the Black Swan Komatiite. It partially overlaps the Black Swan Deposit. Cygnet is up to 40 metres thick, 190 metres long, dips 70 degrees north-east, with a vertical extent of 300 metres with Ni grade and thickness declining with depth. The gangue is coarsely crystalline interlocking plates of iron bearing magnesite breunnarite with minor quartz, with fine grained magnetite and sometimes chromite.

Mineral List

Antigorite Chalcopyrite Magnesite

Magnetite 'Olivine' Pentlandite

Polydymite Pyrite Talc

Vaesite Violarite

11 entries listed. 10 valid minerals.

References

External Links