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The Bushveld Complex

The Bushveld Complex, found in the northern part of South Africa, is the world s largest layered intrusion. The complex plays host to over half of the world s platinum, chromium, vanadium and refractory minerals.

The complex is dated at 2.06 Ga, and is situated in the northern part of South Africa (Figure 1). The intrusion is divided into four limbs - the northern, southern, eastern and western limbs (Figure 2).

Click here for pictures of the Bushveld Complex

Figure 1: Map showing the position of the Bushveld Complex in South Africa

Geology of the Bushveld Complex
The Bushveld Complex is made up of the Rustenburg Layered Suite, the Lebowa Granites and the Rooiberg Felsics (Figure 2). It is underlain by rocks from the Transv l Supergroup and overlain by Karoo sediments

Figure 2: The geology of the Bushveld Complex

The Rustenburg Layered Suite contains mainly mafic rocks and is divided into a number of different zones. The marginal zone is found around the edge of the intrusion, while from the base of the complex up is the Lower Zone, the Critical Zone, the Main Zone and lastly the Upper Zone. The main rock types and minerals found in these zones are listed in the table below:

Zone Minerals Rock Types
Upper Ol, Cpx, Plag, Mgt, Apatite Gabbro, Anorthosite, Magnetite
Main Opx, Cpx, Plag Pyroxenite, Anorthosite, Gabbronorite
(Upper) Critical Opx, Plag, Cr Pyroxenite, Anorthosite, Norite, Chromitite
(Lower) Critical Opx, Cr Pyroxenite, Chromitite
Lower Ol, Opx Dunite, Pyroxenite, Harzburgite

where Ol = Olivine
Opx = Orthopyroxene
Cr = Chromium
Plag = Plagioclase
Cpx = Clinopyroxene
Mgt = Magnetite

Economic Importance
The chromitite seams in the Critical Zone are divided into the lower (LG), the middle (MG) and the upper groups (UG), with the LG6, UG1 and UG2 being of greatest economic importance.

The magnetite in the Upper Zone is rich in Vanadium.

The Merensky Reef is found between the Critical and the Main Zone, and is rich in Platinum Group Elements (PGE?s) - i.e. platinum, palladium, rhodium, iridium, osmium and ruthenium.

Recommended Reading
McCarthy, T. & Rubidge, B. (2005). The Story Earth and Life. Struik, Cape Town. 333pp.

Eales, H.V. (2001). "A First Introduction to the Geology of the Bushveld Complex and those aspects of South African Geology that relate to it." Popular Geoscience Series, No. 2, Council for Geoscience, Pretoria, 84pp.