Mystery Gold Mine (Mystery Zone), Mullingar, Kalgoorlie-Boulder, Kalgoorlie-Boulder Shire, Western Australia, Australiai

Regional Level Types
Mystery Gold Mine (Mystery Zone)	Mine
Mullingar	- not defined -
Kalgoorlie-Boulder	- not defined -
Kalgoorlie-Boulder Shire	Shire
Western Australia	State
Australia	Country

The Mystery Gold Mine is located 2 kilometres north-east of the Kalgoorlie city centre. There are four shallow pits accessing regolith gold- Sir John, Union Club, Mount Percy, and Mystery, which are virtually co-joined. While by no means the most interesting geological deposits in Western Australia, they have been much studied, due to their proximity to Kalgoorlie and the Golden Mile.

By 1932, it is reported the mine had produced 13 189 tonnes of ore for 3376 ounces of gold. GML 4347E. Modern exploration took place from 1977 by Occidental Minerals Corporation of Australia. Mystery was mined from 1987.

At the north end of the Mystery area is shallow 10 metre clay and pisolith filled channels. At the southern end is massive lateritic duricrusts. The mine is part of a hinge zone and steep east dipping limb of the Kalgoorlie Anticline. Gold is associated with quartz veins and felsic porphyry intruding the Hannans Lake Serpentine.

In the Mystery Zone, the serpentine includes talc-chlorite-carbonate rocks, intruded by felsic porphyry, with numerous ultramafic xenoliths. These have been altered to green fuchsite-carbonate rock, especially near the contacts with porphyry.

The regolith weathering front is 50 metres from the surface, extending to 100 metres in fractures. From the basal saprock, the regolith consists of saprolite, 40-50 metres thick of kaolin, some muscovite, quartz, fuchsitic ultramafic rocks, and chlorite. Where saprolite has developed from porphyry it is bleached, whereas from ultramafic rocks is fuchsite green. Secondary alunite is found in the upper saprolite.

Next is mottled and plasmic clays, 10-15 metres thick, pale green-grey kaolin, strongly coloured with Fe oxides. In plasmic zones, the fe Oxides form diffuse impregnations throughout, while in mottled clays it forms pisoliths, and high irregular nodules and aggregates. Also relict muscovite.

The lateritic residuum is 1-5 metres thick, of nodular and pisolith gravels, with massive talc-chlorite-carbonate duricrust, and Golden Mile dolerite, consisting of goethite and hematite, with some maghemite near the surface.

Calcareous soil forms the top metre, consisting of calcite loam, with calcite nodules, and abundant Fe pisoliths and nodules. In the east and north sections this is replaced by calcareous red clay soil.

Primary mineralisation is found along a length of 800 metres, separated from the Mount Percy zone by 300 metres of intermittently mineralised rock. At Mystery silver can be up to 50% of the content with the gold. It occurs in quartz-carbonate veinlets, with minor pyrite, and trace chalcopyrite, galena, sphalerite, arsenopyrite, and millerite.

Mineralisation is confined to irregular, steep dipping lenses in fuchsite-carbonate alteration zones at porphyry contacts, intruding the Hannans Lake Serpentine. Increased S, Sb, As, Ag, Te and W is found in the mineralised zone. Gold distribution is patchy in the regolith. A weak supergene enrichment area, 10-15 metres thick, is found below 17 metres of the surface, and also at 30-40 metres deep. A leached zone 5-10 metres thick occurs 2-4 metres from the surface. Above this is widespread gold enrichment close to the surface .

Other Regions, Features and Areas containing this locality

References