How did South Africa come to be so well endowed with minerals?

More than four billion years ago the Earth’s crust was molten. When began to cool, continental nuclei, the cores around which continents later grew formed. As it happened, south central Canada, Brazil, part of Russia, Australia, and South Africa all contain continental nuclei. That is, they possess the world’s oldest, or Archaean, rock, which is just the sort of rock that contains gold, iron, and manganese. But age isn’t enough. For rocks to yield their minerals readily, they must also be exposed. In this, too, South Africa was fortunate. While Brazil’s Archaean rock came to be covered by the Amazonian rain forests, Canada’s by glacial debris, Russia’s with steppes, and Australia’s with the thick soils of the outback, South Africa’s remained relatively unchanged by younger geological events. Even weathering has helped. The ancient rocks have eroded in such a way that some of their minerals, particularly gold; have been reconcentrated in sediments near the surface.

This explains South Africa’s wealth of easily accessible gold, iron, and manganese, but what of its other treasures-platinum, chromium and diamonds? These are the consequence of another bit of luck: The tip of Africa happens to be a ‘geological crossroads,’ where continents have built up and broken apart over time. When continental nuclei rupture, molten rock rises through the rifts, resulting in igneous rocks that fill the cracks. There are many such extrusions of igneous rock in the world, but the effects of rifting have been especially dramatic in South Africa. About 1.8 billion years ago South Africa’s Bushveld Complex, the biggest single igneous rock body on the face of the Earth (roughly the size of Ireland), was formed, leaving behind huge deposits of chromium and platinum.

Rifting also led to the formation of diamond fields 100 million years ago. The molten rock that rose from rift inter sections in South Africa contained pipes of kimberlite, which carry fully formed diamonds from great depths. Again South Africa isn’t unique in this regard. Arkansas, Wyoming, and Western Australia have had rifting, and have diamonds very similar to the ones in South Africa. But their kimberlite pipes aren’t as large or well formed, and therefore can’t carry as many big, high-quality diamonds up to the surface. Once more, South Africa was just plain lucky. Its kimberlite pipes are deep and protrude prominently through the brittle, ancient crust. Geological fate has indeed been very kind to South Africa. The rock there is readily available to be mined.

More reading:
Mining industry of South Africa (Wikipedia)

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