Ripon Hills manganese prospects, Ripon Hills District, East Pilbara Shire, Western Australia, Australiai

Regional Level Types
Ripon Hills manganese prospects	Group of Prospects
Ripon Hills District	Mining District
East Pilbara Shire	Shire
Western Australia	State
Australia	Country

The main group of deposits cover an area 6 kilometres by 5 kilometres, north of the Ripon Hills Road, between the Nullagine River and Yilgalong Creek crossings.

Longeach Oil Ltd formed a subsidiary called the Longreach Manganese Pty Ltd (in another source Longreach Metals NL, and in another Australian Longreach Metals Company).

The deposits were known from the 1950's, but extensively explored by Longreach Metals NL from 1968 to 1972. The company appeared on the verge of commercial production with a purchase agreement with Nippon Steel. The tenements, plant and equipment had been purchased from the Mount Sydney Manganese Pty Ltd at Woodie Woodie. However, it appears to have come to nought. In 2009, the deposits were explored by Jupiter Minerals.

Ripon Hills is a dissected fault plateau, formed by the uplift blocks of gently dipping Proterozoic shales, Pinjian cherts and Carawine dolomite. The shale is Mn and Fe enriched, with overlying chert breccia.

The ore deposits are Fe and Mn erratic supergene replacement of shale, and leaching of other minerals. The ore is fine grained pyrolusite, intergrown with fine grained hematite, with locally extensively altered bixbyite and braunite, cryptomelane, lithiophorite aggregates, hosted by kaolin.

At a cut-off rate of 20% Mn, the resource of 12 Mt, grading at 24.6% Mn, and 23% Fe. Much of the remaining deposit is low grade. In 1972, the proven resource was 20 Mt, with Indicated and Inferred resource of 50 Mt. It was also stated there was a small iron ore deposit of 10 Mt of 64-68% Fe.

It has been formed by the laterite weathering of Proterozoic ferruginous-manganiferous shales, forming supergene Fe-Mn ores in the upper 11 metres from the surface, caused by irregular substitution of the parent rocks by Fe and Mn oxyhydroxides during leaching and intensive removal of other components.

The old derelict processing plant remains, surrounded by overgrown piles of manganese, with various very small isolated manganese pits in the surrounding area. The site is not easily accessed, the track from the north off Warrwagine Road, rather than Rippon Hills Road. It goes for miles in a southerly direction along creeks, and through hills, and is likely in a poor state. The track continues west of the old processing plant onto the flats and for several kilometres to an unusual large, and equally little visited sinkhole.

Other Regions, Features and Areas containing this locality

References