We await next drill results, we are lucky to get in for a early price, Mulga Tank deposit has been compared with Mount Keith nickel project. Purchased by BHP in 2005 for 9 billion!!
Mount Keith is one of the world’s largest low grade open pit nickel mines, with total resources of 477 Mt (cut off of 0.4% Ni).
Located 90 km NNE of Leinster.
Considered the largest open cut nickel mine in the world. 85 kilometres south of Wiluna. Discovered in 1968 by local pastoralist Jim Jones, who convinced a friend with a drilling rig to drill one hole in some gossanous material, discovering disseminated Ni sulphides at a depth of 70 metres. The deposit was subsequently explored by the Metals Exploration/Freeport of Australia joint venture, with ore production starting in 1994 by Western Mining Corporation. The mine was acquired by BHP Billiton in 2005 when it took over Western Mining Corporation. The pit is 2.4 kilometres long by 1.4 kilometres wide by 300 metres deep. The deposit is mineralogically diverse due to hydrothermal alteration overprinting.
The location is of interest to rare species collectors. Woodallite was discovered here in 2001 by Ben Grguric et. al., and is found only at Mt Keith and the nearby West Jordan nickel prospect. At Mt Keith it occurs as whorls and clusters of minute platelets up to 6mm across in lizardite-brucite altered dunite, also with associated species chromite, iowaite, pentlandite, magnetite, and tochilinite. It forms as the result of hydrothermal alteration of primary magmatic chromite by Cl rich solutions at temperatures less than 320 degrees. Mt Keith is also the type locality for Mountkeithite discovered in 1981, and found at only four localities worldwide, including the nearby West Jordan nickel prospect. The mine contains many species. A very limited number and variety are in circulation. Violarite/pyrite specimens have been known to degenerate over the years.
The deposit is located in a greenstone belt containing lower interbedded volcanics, pyroclastics, shale and chert. It is overlain by an upper sequence of pillowed basalt, a thick suite of volcaniclastic rocks, a zone of komatiite and an upper series of thin komatiite flows, layered **bro and high magnesium and tholeiitic basalt.
The mine is contained within the Mount Keith ultramafic complex, a thick komatiitic dunite body as subvolcanic sills emplaced within or below an extrusive komatiite pile. The dunite bodies are not an integral or neccessary part of the komatiite flow field. Nickel mineralisation is within a zone of orthocumulate rich ultramafic body called MKD5. The orebody strikes for 2 kilometres, to at least 500 metres deep.
The MKD5 area shows a basal olivine orthocumulate, then an un-mineralised adcumulate grading to a layered olivine-sulphide adcumulate-orthocumulate containing the orebody, and finally orthocumulate **broic ultramafic rocks.
No relict olivine remains, and it has been completely serpentinized. The overlying mafic/ultramafic rocks have been altered to an albite-actinolite-epidote-chlorite assemblage. It has also been strongly structurally controlled altered with intense carbonate-talc on the outer margins of MKD5, and along faults. The hanging wall and footwall show strongly sheared ultramafic rocks.
The primary sulphide zone contains lobate aggregates 1-2mm across, mainly pentlandite with magnetite. 20% of the orebody is pentlandite-millerite and heazlewoodite and magnetite. The Ni-Fe sulphides show oxidation/weathering
where pyrrhotite has been replaced by marcasite, pentlandite replaced by violarite, violarite by millerite and finally the decomposition of the sulphides. The serpentine host rock is bleached in this zone and with high weathering the serpentine is replaced by clay minerals, with alot of quartz and dolomite. Overlying this is a ferruginous zone dominated by goethite, clay minerals and the absence of
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