Ilmars prospect, Alice Downs Station, Halls Creek Shire, Western Australia, Australiai

Regional Level Types
Ilmars prospect	Prospect
Alice Downs Station	- not defined -
Halls Creek Shire	Shire
Western Australia	State
Australia	Country

Located in the northern Ilmars Range, about 30 kilometres north north-east of Halls Creek, and 5 kilometres east of the Great Northern Highway. Described as 200 yards from the road to Saunders Creek, on the crest of a sharp ridge 50 feet high. Much explored, with mineralisation found, but nothing yet economic. Cu-Pb-Zn prospect. First explored by Peko Mines NL in 1963.

The deposit occurs is schists, variably quartz-sericite, quartz-chlorite, carbonate rich, and graphite schists, with interbedded tuff, limestone, calcareous mudstone, shale and chert. Oxidation reaches 18 to 30 metres below the surface.

Mineralisation occurs for 1800 metres long, with lower grades another 3000 metres further south. Pyrite and/or pyrrhotite dominates, with sphalerite, and minor galena, chalcopyrite, trace arsenopyrite and tetrahedrite-tennantite. The sulphides range from fine grain disseminations to semi massive concentrations. Most of the mineralisation is in quartz and feldspathic schist.

The prospect was discovered with exposed surface gossans in 1963. These are orange or red/brown soft porous limonitic rocks, commonly showing boxwork, with malachite, cuprite, hydrozincite, minor azurite, chalcocite, covellite, native copper, and rare smithsonite and cerussite. The gossan was found in two sections, of thinly bedded dolomitic shale separated by a barren zone. The gossans strike north for 850 feet, average 60 feet wide, dips 65 degrees west. They are split by a leached zone 15 feet wide of unmineralised tremolite. The secondary copper minerals are abundant as bands, patches, and small lenses.

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References