Bushveld Igneous Complex

The Bushveld Complex in South Africa is one of the largest Intrusivkomplexe basic melting of the Earth and is distinguished by its magmatic layers (Layered Intrusions ). The concentration of platinum group elements deposits has geopolitical importance.

Location and size

The complex is situated in the border area of the four provinces of West, Gauteng, Mpumalanga and Limpopo in South Africa. It was formed about 2.06 billion years. In an open-minded area of ​​460x245 km, the total thickness of the complex is up to 8 km.

Only parts of the complex are open-minded; a total of four bowl-shaped intrusive body ( praise ) are postulated to geophysical data base. The Praise consist of mafic and ultramafic rocks that occur on all sides with 10 ° to 20 ° towards the center. The result is a saucer- shaped body which is geologically referred to as Lopolith.

Composition

The basic magmas from which the praise arose, had a magmatic layering, so that a layer intrusion originated. The magma, with a lower density than the surrounding rock, rose by from the mantle in the area of the continental crust. During crystallization, the magma was chemically constantly changing due to the formation of relatively heavy crystals (eg olivine ), so that a fractional crystallization as referred to Norman L. Bowen held that igneous differentiation.

The base of the complex formed by dunites and peridotites; followed by pyroxenite and norite, from which the stone Impala is produced.

The Merensky Reef within the complex base is an ortho- magmatic deposit, which is considered the world's premier platinum group deposit. Chromium, copper and nickel are present workable.

The top section of form granophyre and granite, which are believed to have originated in the wake of intrusion by melting of continental crust by the basic magma and mixing of magmas.