Where do the biggest diamonds come from? Geology now has answers

10 hours ago

CLIPPIR diamonds are rare superdeep diamonds forming more than 400 km deep in Earth's mantle transition zone, unlike ordinary diamonds that form at depths up to 200 km.
They originate from ancient oceanic crust that was dragged deep into the mantle by plate tectonics and transformed into diamond under extreme conditions.
New research on olivine chemistry in kimberlite rocks reveals that CLIPPIR diamonds are associated with iron-rich domains in the mantle, linked to hydrothermally altered basaltic oceanic crust.
The dense iron-rich rocks hosting these diamonds cannot rise passively; they likely require mantle plumes for upward transport before being stored at the base of continental roots for hundreds of millions of years.
Kimberlite magmas eventually carry these diamonds to the surface, recording a long geological journey from seafloor to deep mantle to surface.
The findings provide a practical tool for diamond exploration: kimberlites with abundant iron-rich olivine have higher potential to host CLIPPIR diamonds, guiding exploration in regions like Sierra Leone and Angola.

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