Deep Impact of the Vredefort Dome

The Bushveld Complex and the Vredefort Dome

©David Fleminger

After the Transvaal Supergroup came the Bushveld Complex, formed when a huge amount of molten rock was pushed from the Mantle into the upper reaches of the Transvaal Supergroup.

This injection of rock into the easily-eroded sediments of the Transvaal Supergroup formed a layered igneous rock complex that covers an area of 60 000 square km’s, making it the largest in the world. The Bushveld Complex also just happens to contain 80% of the world’s Platinum. Yay for us! But it wasn’t all fun and games. About 2 billion years ago, a major meteorite slammed into the ground about 120k’s south-west of Joburg. It hit so hard that the rock was lifted up, 10km’s above its original position.

The result was the Vredefort Dome, the largest and earliest-known meteorite impact site on Earth (originally measuring up to 250 km from side to side, although much of this crater has now been filled in). This impact also conveniently buried the gold deposits that were, at the time, lying close to the surface, thus protecting them for future exploitation.

But the Vredefort Dome was not always considered an impact structure and, over the years, various proponents put forward their own theories. However, a recent study has cleared things up a bit, and the controversy about the origin of the Dome seems to have been settled by those feisty geologists.

Although I am still unsure how an impact can create a dome and not a crater, I have to bow to the superior knowledge of my betters and declare that a meteorite done it after all!

By David Fleminger

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