Chapter 8: The Northern Limb of the Bushveld Complex: A New Economic Frontier
The northern limb of the Bushveld Complex of South Africa contains a diverse array of Cr, Ni-Cu-platinum group element (PGE), Fe-V mineralization in mafic-ultramafic rocks and Sn mineralization hosted in granites. The limb has historically been underexplored compared to other parts of the Bushveld Complex and currently represents one of the world’s most interesting exploration frontiers. Successful low-cost open-pit mining of the thick Platreef Ni-Cu-PGE deposit, coupled with rising costs and limited scope for mechanization associated with narrow reef-type deposits in the eastern and western Bushveld, have driven efforts to locate similarly wide magmatic sulfide orebodies at surface or at reasonably shallow depths elsewhere in the northern limb, including recent discoveries of the Flatreef- and Main zone-hosted PGE deposits in the troctolite unit, at Aurora, and in the lower (F) and upper (T) mineralized zones at Waterberg. The Flatreef is hosted within a more consistent series of stratigraphic units than the more varied Platreef located updip, and while it shows similarities in terms of rock types and some geochemical features with the upper Critical zone of the eastern and western Bushveld, strict time equivalence remains to be proven. The various styles of Main zone-hosted PGE mineralization, on the other hand, have no known equivalents in the other limbs of the Bushveld Complex and seem to represent processes and events confined to the northern limb. Potential links based on similar rock types and metal budgets between Aurora and the Waterberg T zone and between the troctolite unit and the Waterberg F zone are attractive but must remain speculative until it becomes clearer whether the northernmost compartment that contains the Waterberg mineralization is linked to the remainder of the northern limb. If both the Flatreef and the Waterberg deposits enter production as planned over the coming decade, they will have dramatic effects on the South African platinum industry and dramatically increase the amount of Pd relative to Pt produced by South Africa due to the Pd-rich nature of all of the northern limb PGE orebodies.