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The Bushveld Igneous Complex (BIC) |
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| The Bushveld Igneous Complex (BIC) is the world's largest known layered intrusion and has an estimated areal extent of 182,000 km2 .The BIC is an enormous, champagne glass-shaped body 370 kilometres across, with its centre buried deep beneath younger rocks but with its rim exposed. It is composed of a series of distinct layers, three of which contain economic concentrations of platinum group elements (PGEs). The principal PGE-bearing reefs are the Merensky Reef and the Upper Group 2 (UG2) Reef, which occur around the Eastern and Western sides ("limbs") of the BIC. A third PGE-rich layer, the Platreef, is found only on the Potgietersrus limb at the north-eastern edge. |
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The BIC contains an ultramafic to mafic unit (the Layered Series), up to 9 km thick, which outcrops as eastern, western and northern lobes surrounding a felsic core of largely granitic rocks. The Merensky Reef, which is the best known and most commonly exploited platiniferous horizon in the Complex, can be traced for at least 240 km along strike and is estimated to contain 60 000 t of platinum group metals in its upper 1 200 m, as well as significant resources of cobalt, copper and nickel. The pyroxenitic Platreef horizon, north of Potgietersrus, is a wide zone containing PGE mineralisation, along with nickel and copper. Of major economic importance is the UG2 (Upper Group 2) chromitite horizon that is being increasingly exploited for its PGEs, particularly in the eastern lobe of the Bushveld Complex. This represents an even larger resource of PGEs than the Merensky Reef.
The BIC also contains almost 70% of the world's reserves of chromite as well as significant resources of vanadium. |
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