Mitchell Plateau Deposit, Wyndham-East Kimberley Shire, Western Australia, Australia
|Latitude & Longitude (WGS84):||14° 51' 58'' South , 125° 50' 19'' East|
|Latitude & Longitude (decimal):||-14.86602,125.83850|
|Köppen climate type:||Aw : Tropical savanna, wet|
(Map- denotes geographic location of the plateau rather than any mine or specimen site. The plateau covers a large area).
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).
Australia's best quartz/epidote combination specimens have come from the Mitchell Plateau, but little is known. Please update Mindat with any information. The reference concentrates mainly on bauxite, but the writer's experience of bauxite deposits in Australia is they are a specimen free zone. While the reference states quartz is very minor on the plateau, quartz crystals are found in cavities in basalt outcropping along the perimeter of the plateau. New specimens have not been seen for many years.
The Mitchell Plateau is in the far north of the Kimberley. An upland averaging 320 metres in height over 30 square kilometres, surrounded by Livingstonia palms, rainforest thickets, rare flora and fauna. It is also 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. 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.
13 valid minerals.
Rock Types Recorded
Select Rock List TypeAlphabetical List Tree Diagram
Entries shown in red are rocks recorded for this region.
This geological map and associated information on rock units at or nearby to the coordinates given for this locality is based on relatively small scale geological maps provided by various national Geological Surveys. This does not necessarily represent the complete geology at this locality but it gives a background for the region in which it is found.
Click on geological units on the map for more information. Click here to view full-screen map on Macrostrat.org
1600 - 2500 Ma
Age: Proterozoic (1600 - 2500 Ma)
Stratigraphic Name: Carson Volcanics
Description: Green to black quartz basalt, in places amygdaloidal and with basaltic volcaniclastic rocks, interbedded massive feldspathic or argillaceous quartz sandstone, laminated siltstone and mudstone
Reference: Raymond, O.L., Liu, S., Gallagher, R., Zhang, W., Highet, L.M. Surface Geology of Australia 1:1 million scale dataset 2012 edition. Commonwealth of Australia (Geoscience Australia).