Research Team Cracks Secret Behind Bushveld Platinum

There are two competing ideas on how platinum deposits are formed, and researchers at the University of the Witwatersrand (Wits) believe they have determined which process is behind South Africa’s Bushveld Complex.

A study published Wednesday (June 19) suggests that the platinum deposits at the Bushveld Complex were created via crystals that grew in situ, directly on the floor of the structure’s magmatic chamber.

The researchers came to this conclusion when their team, led by Dr. Sofya Chistyakova, examined the Merensky reef of the Bushveld Complex, which holds a huge amount of the world’s platinum.

Crucially, they figured out that while the Merensky reef was forming, portions of its chamber floor were irregular because of circular depressions or potholes.

“Our key discovery is that the entire Merensky reef package in these potholes may develop as a ‘rind’ covering all the chamber floor depressions and culminations, even where these are vertical or overhanging,” said Chistyakova.

The second idea on how platinum deposits are formed is through the settling of crystals on the floor of a magmatic chamber through gravity. According to the researchers, the pothole findings show it isn’t possible that the Bushveld Complex platinum deposits could have been formed in this way.

That’s because sinking crystals from the Merensky reef would not have been able to cut through the solid rocks that form the overhangs of the potholes.

“This is the most fundamental conclusion of our work and it can probably be applied to platinum deposits in other layered intrusions as well as potentially extended to other types of magmatic deposits, for example, chromite and Fe-Ti-V magnetite ores in mafic-ultramafic complexes,” said Chistyakova.

Most of the world’s economically viable platinum deposits occur as reefs in layered intrusions of silicate rock containing sulfides enriched in platinum-group elements.

South Africa is the world’s largest producer of platinum by far, accounting for about 75 percent of global output. The Bushveld Complex itself contains more than half of the world’s platinum, chromium, vanadium and refractory minerals.

As of 12:45 p.m. EDT on Thursday (June 20), platinum was trading at US$803 per ounce. 

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Securities Disclosure: I, Nicole Rashotte, hold no direct investment interest in any company mentioned in this article.