PLATINUM-GROUP ELEMENTS IN SOUTHERN AFRICA—MINERAL INVENTORY AND AN ASSESSMENT OF UNDISCOVERED MINERAL RESOURCES

The main sources of platinum-group elements (PGE) occur only in three countries in the world (South Africa, Zimbabwe, and Russia). Mineral resource and reserve information was compiled for ultramafic and mafic rocks in southern Africa, an area that hosts much of the world’s PGE resources, using information in the public domain. Additional mineralized rock is likely to occur in extensions to the well-explored and characterized volumes of mineralized rock. To assess the undiscovered reef-type PGE resources, we used information from areas with known mineral resources to develop a geospatial model for metal surface density, which incorporates variations in dip, mining width, rock type, and grade. Undiscovered resources associated with contact-type deposits were assessed using grade-tonnage models and an estimate of the number of undiscovered deposits.

As of 2012, exploration and mining companies have delineated more than 20 billion metric tons (t) of mineralized rock containing 42,000 t of platinum, 29,000 t of palladium and 5,200 t of rhodium primarily in mafic and ultramafic intrusions, the Bushveld Complex and the Great Dyke. Underexplored extensions of stratabound PGE deposits in the Bushveld Complex in South Africa may contain 65,000 of platinum, palladium, and rhodium to a depth of 3 km. Rocks enriched in PGE, that occur near the contact of the Bushveld Complex with older Transvaal Supergroup sedimentary rocks, may contain 1,100 t of platinum and 1,370 t of palladium (mean estimate to a depth of 1 km). A stratabound PGE deposit in the Great Dyke in Zimbabwe may contain 6,900 t of undiscovered platinum, palladium, and rhodium. By comparison, the global net demand for PGE in 2012 was approximately 460 t. Since the 1920s, mining has recovered 7,200 and 107 t of PGE from the Bushveld Complex and the Great Dyke, respectively.

The large layered intrusions in southern Africa, the Bushveld Complex and the Great Dyke, are now and will continue to be a major source of the world’s supply of PGE. Mining will not deplete the identified mineral resources and reserves or potential undiscovered mineral resources for many decades; however, in the near-term, PGE supply could be affected by social, environmental, political, and economic factors.