Quote:
Originally Posted by hhEb09'1
Mantle plumes have been theorized to extend to the core, maybe 3000 km deep. Kimberlite pipes are narrow extrusions that probably originate only ~100 km deep.
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Quite right - maybe even a bit more than 100 km.
I hadn't picked up on the OP's notion that South Africa is unique in this regard (gold & diamonds). It isn't; both minerals are found elsewhere in a single country, although SA might be unusual in that, for a not-so-big country, it has an inordinate wealth of both.