Bushveld igneous complex
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The Bushveld Igneous Complex contains some of the richest ore deposits on Earth. The reserves of chromium, platinum, palladium, osmium, iridium, rhodium, and ruthenium are the world's largest, and there are vast quantities of iron, tin, titanium, and vanadium. Dimension Stone is also quarried from parts of the Complex.
The Complex includes layered mafic intrusions (the Rustenburg Layered Suite) and a felsic phase. It has its geographic centre located north of Pretoria in South Africa at about 25° S and 29° E.
It covers over 66,000 km², an area the size of Ireland. The complex varies in thickness, sometimes reaching 9000 meters thick. Lithologies vary from largely ultramafic peridotite, chromitite, harzburgite, and bronzitite in the lower sections to mafic norite, anorthosite, and gabbro toward the top, and the mafic Rustenburg Layered Suite is followed by a felsic phase (the Lebowa Granite Suite).
The origin of the vast complex is attributed to a series of huge arcuate differentiated lopolithic intrusions. The Lebowa Granite Suite has been dated at 2.054 billion years (2.054 Ga).
The orebodies within the complex include the UG2 reef containing up to 43.5% chromite, and the platinum-bearing horizons Merensky Reef and Plat Reef. The Merensky Reef varies from 30 to 90 cm in thickness. It is a norite with extensive chromitite and sulfide layers or zones containing the ore. The Reef contains an average of 10 ppm platinum group metals in pyrrhotite, pentlandite, and pyrite as well as in rare platinum group minerals and alloys.
[edit] See also
[edit] References
- Viljoen, M.J. & Schürmann, L.W. (1998), 'Platinum-group metals' in Council for Geoscience Handbook 16, Mineral Resources of South Africa, edited by M.G.C. Wilson and C.R. Anhaeusser. Pretoria: Council for Geoscience, ISBN 1-875061-52-5
- Guilbert, John M., and Park, Charles F., Jr. (1986) The Geology of Ore Deposits, Freeman, ISBN 0-7167-1456-6
