The PGM resources of the Bushveld Igneous Complex (BIC) were discovered by Hans Merensky and Andries Lombaard in 1924. Within the complex, three horizons, the Merensky Reef, UG2 Chromitite and the Platreef are mined for PGMs and make the BIC the largest PGM resource in the world. Platinum and palladium production from the BIC represents approximately 75% and 40% of annual global production respectively.
Estimated platinum & palladium resources
In 1999, Professor Grant Cawthorn, the Platinum Industry's Professor of Igneous Petrology at the University of Witwatersrand, South Africa, published a new estimate of the platinum and palladium resources of the BIC.
For his calculations, Cawthorn assumed a maximum mineable depth of 2km, close to the current maximum depth of extraction. Where possible, estimate calculations were based on 1998 geological data from mining companies. These were extrapolated for other areas of the BIC where data was scarce or non-existent. The calculations could be made with the necessary level of confidence due to the remarkable continuity and uniformity of the PGM bearing horizons.
Working under the guidelines of the SAMREC Code Professor Cawthorn estimated proven and probable reserves of platinum and palladium at 203.3 million troy ounces, (6,323 tonnes) and 116.1 million troy ounces (3,611 tonnes), respectively. In addition to these reserves, inferred resources were estimated at 939 million troy ounces (29,206 tonnes) of platinum and 711 million troy ounces (22,115 tonnes) of palladium.
In 2010, Professor Cawthorn published a supplementary paper in which he demonstrated the level of confidence which can be applied to his earlier estimates.
There is potential for these PGM resource estimates to be increased further, both by mining the currently exploited ore bodies at depths below 2 kilometres and by mining other PGM bearing horizons in the BIC.
It can be inferred from the uniformity of the PGM reefs in the upper 2 kilometres of the BIC that these ore bodies will continue for considerable distance downwards, yielding similar grades of PGM. Already, drilling programs are investigating the Merensky Reef and UG2 horizons below 3 kilometres in depth, although considerable exploration work will have to be performed before these potential down-dip extensions can be classified as a PGM resource.
The additional investment necessary to work these deposits would also be considerable, as working temperatures and transportation costs increase with depth. However, technological advances in the South African gold industry have now made deposits viable at a depth of 4 kilometres and it is reasonable to expect that this technology will be transferred to the PGM mines over time.
PGMs are also present in horizons which underlie the Merensky and UG2 reefs in the BIC. These could be exploited when shallower horizons have been worked out.
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