Mitchell Plateau, Wyndham-East Kimberley Shire, Western Australia, Australiai

Regional Level Types
Mitchell Plateau	Plateau
Wyndham-East Kimberley Shire	Shire
Western Australia	State
Australia	Country

The Mitchell plateau area is located some 600km west south-west of Darwin and is at an altitude of approximately 292m above sea level.

An aluminum (bauxite) operation under study only during 1984. 410 million tons of reserves estimated (1984). Owned by Mitchell Plateau Bauxite Co. (consortium of CRA, ALCOA, Billiton, Sumimoto & Marubeni).

The Mitchell Plateau is an area of immense beauty, and huge waterfalls. It is remote. Europeans first explored the area in 1921. It is unlikely it will ever be mined commercially. The environmental hurdles, and public fuss of large scale strip mining in one of Australia's premier wilderness regions, should kill off any such projects.

It hasn't stopped some from trying. The mid 1960's, a company called Amax set up camp to explore for bauxite. Detailed exploration occurred between 1965-1971. The tenements were sold in 1980 to the Mitchell Plateau Bauxite Company and Alcoa of Australia Limited, and more exploration took place from 1980 to 1983 through drilling and trial mining. Several other companies have taken over the tenements since, only to realise it is a pointless exercise.

The plateau (and bauxite deposits) occur in sections called the South, Central and North Plateaus, with several outliers including Lone Dingo to the north-west, and Debatable Point, Parker's Point, and Jack's Folly to the north-east. North of the Mitchell Plateau is another bauxite deposit at the heavily indented and even more remote Cape Bouganville on the coast.

Bauxite at Mitchell Plateau is gibbsite with minor boehmite, and goethite. Regionally there is the lower 900 metre thick King Leopold Sandstone, overlain with the 600 metre thick Carson Volcanics, in turn overlain by the Warton Sandstone. The King Leopold Sandstone is white and locally ferruginous, strongly jointed and faulted, causing deep dissected terranes. The Warton Sandstone is coarse to medium grained sandstone with minor feldspathic sandstone. The Carson Volcanics is altered finely grained basalts with numerous pillowed lava flows and interbedded sandstone, siltstone and tuff.

The lithology shows an upper overburden of earthy brown to red brown iron oxides and clay with common bauxite and laterite pebbles. Next is a massive ferruginous laterite with some nodules of hematite, goethite and maghemite. The next layer down is the bauxite in the form of gibbsite of variable grades and thickness. Then an up to 5 metre thick clay layer with ferruginous nodules with many interconnected voids. Finally, up to 30 metres thick of kaolinite clay with minor montmorillonite and oxides of titanium and iron.

Gibbsite is the most abundant species making up 25%-60% of the mineralised layer. Its main interest is the variety and complexity of textures occurring throughout the deposit. It occurs as fragmental, or hard white massive gibbsite, nodular, mottled, cemented pisolitic, spongy with many small voids, tubular, and vermicular with many small channelways within the ore. Boehmite accounts for between 1%-10% of the mineral assemblage, highly variable in amounts over short distances.

Most of the clays is kaolinite with minor montmorillonite and trace illite. Quartz is rare being less than 1% of the minerals, found as discrete crystals in cavities, in the upper portion of the deposit. Goethite is the most common iron oxide near the base of the profile, while hematite is dominant near the surface. Maghemite occurs in small quantities in the upper ferruginous bauxite layer, and on the surface. Titanium oxides occurs as fine sub-microscopic disseminations of anatase, and is less than 1% of the mineral assemblage. Up to 50% of the heavy mineral component is rutile, and 10% ilmenite.

Fossils

This region is too big or complex to display the fossil list, try looking at smaller subregions.

Localities in this Region

References