Six Mile Well Ni deposit, Yakabindie Station, Leonora Shire, Western Australia, Australiai

Regional Level Types
Six Mile Well Ni deposit	Deposit (Active)
Yakabindie Station	Station (farming)
Leonora Shire	Shire
Western Australia	State
Australia	Country

Located 7 km south south east of Mount Falconer.

40 kilometres south of the Mt Keith Mine, between Mt Keith and Leinster, east of the Goldfields Highway. Discovered by Anaconda in August 1970, when Anaconda geologists diamond drilled an induced polarisation anomaly. The anomaly was found to have been caused by a black slate horizon, however, the drilling also fortuitously intersected disseminated nickel sulfides in serpentinite. Later Dominion Mining planned to start an open pit in the late 1980's, and sunk a 100 m deep test shaft in the deposit in 1995, however it was opposed by local indigenous groups due to the likely destruction of sacred sites. The Yakabindie nickel prospects are now (2013) part of BHP Nickel West Mt Keith operations. Open pit mining was initiated in 2019 and ore is presently being trucked and processed at the Mount Keith concentrator.

The Six Mile Well Deposit is the largest of several nickel prospects in the area, with a relatively low grade Ni, and complex geology.

The Six Mile Well lens is south plunging, dips almost vertically west, and shows nickel grades at 0.6% and copper at 0.01%. Its western contact is conformable with the overlying westerly dipping meta-sediments, while the eastern contact is partly intrusive and partly faulted. Supergene alteration occurs to 150 metres, and the oxidised zone is 30 to 80 metres thick.

The Six Mile Deposit lens is 1400 x 200 metres as a north-south elongated serpentinised dunite-olivine core, surrounded by a further 100 metre wide envelope.

The dunite-olivinite core hosts most of the mineralisation, and has almost completely been serpentinized to lizardite and antigorite, with only minor fresh olivine left. There are also in this, zoned chromite grains rimmed with magnetite. There is a zone 50 to 100 metres wide running the full length of the dunite core and into the peridotite rocks to the north of pentlandite and pyrrhotite, with minor pyrite and chalcopyrite, interstitial to the olivine pseudomorphs. Where the sulphides are poorly developed, millerite, heazlewoodite and godlevskite is found.

Around the lens is an envelope containing lizardite or antigorite, with minor brucite, tremolite, talc, magnesite, and chromite. There is also a narrow, 850 x 25 metre, zone of mineralisation in the western part of the envelope, containing pentlandite and pyyrhotite, with minor nickeline, maucherite, cobaltite, and pyrite, all mainly in carbonate veinlets forming networks in the southern portion, and ragged blebs of pentlandite and pyrrhotite in peridotite in the northern portion.

The deposit is in the Agnew-Wiluna Greenstone Belt. Six Mile Deposit is at the northern end of a series of linked Ni pods, such as Goliath North and Sheba amongst others. The sequence of rocks units at Six Mile from the highest is as follows:
1. Jones Creek Conglomerate of granitoid/feldspar conglomerate, mafic conglomerate, and ultramafic para-schist.
2. a sedimentary geologic break
3. Serp Hill meta-peridotite, 100 metres thick of serpentinised olivine peridotite with cumulus textures.
4. Cherty meta-sediment marker horizon a few metres thick.
5. A layered series 600-800 metres thick, of basaltitic to ultramafic flows and intrusive rocks, interlayered with meta-basalt and meta-gabbro to pyroxenite in the upper layers, and magnesian meta-basalt and spinifex textured ultramafic flows in the lower part.
6. Cherty meta-sediment marker horizon a few metres thick.
7. dunitic lenses 300-500 metres thick of serpentinized black dunite-olivine grading to dark green-grey olivine peridotite, with disseminated nickel sulphides in some of the lenses.
8. Volcanogenic meta-sediments, 500-700 metres thick, of poorly bedded quartz, actinolite, garnet, biotite, chlorite and andesine bearing rocks, some pyroclastic in origin, and some cherty and slaty horizons.
9. Cherty meta-sediment marker horizon a few metres thick.
10. Meta-basalt: up to 500 metres thick of tholeiitic meta-basalt with some lenses of magnesian meta-basalt near the top.

Other Regions, Features and Areas containing this locality

References