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The Merensky Reef of the Bushveld Igneous Complex

C. A. Cousins
C. A. Cousins
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January 01, 1969


The Merensky Reef of the Bushveld Igneous Complex, a regular layer of pyroxenite, mineralized by the sulfides of nickel, iron and copper, together with thin bands or concentrations of chromite, contains by far the greatest known ore-reserve of platinoids in the world.

The Reef occupies a specific position, within a regularly layered sequence of anorthositic, gabbroidal and pyroxenitic rocks. The Mafic Zone of the Bushveld, in which it is found, can be divided into readily recognizable sub-zones, with definite markers, and has an almost identical succession in both East and West Belts.

The reef contains the platinoid metals, principally as sulfides, but also as ferroplatinum, together with arsenides, tellurides, bismuthides, antimonides and possibly stannides and selenides.

The reef has been followed over a total distance of 155 miles and to vertical depths of greater than 6,000 feet. All evidence suggests that the Merensky Reef is the basal portion of a relatively thin unit-heave of magma with a clear pattern of magmatic differentiation. The heavy minerals appear to be primarily precipitated by gravity from solution in the magma. The Merensky unit appears to be one of many heaves that built up the Mafic Zone.

The amazing regularity of the reef and its associated rocks is in places disturbed by depressions and domes, mostly small but a few are large. Alteration pegmatites associated with these structures and evidence indicating the rocks were solid when they were formed, suggest a probable mode of genesis.

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Society of Exploration Geophysicists Geophysical Monograph Series

Magmatic Ore Deposits

H. D. B. Wilson
H. D. B. Wilson
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Society of Economic Geologists
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Publication date:
January 01, 1969




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