Journal article

Ancient metasomatism recorded by ultra-depleted garnet inclusions in diamonds from DeBeers Pool, South Africa

A Banas, T Stachel, D Phillips, N Shimizu, KS Vijoen, JW Harris

Lithos | ELSEVIER | Published : 2009

Abstract

Peridotitic garnet inclusions in diamonds from the DeBeers Pool mines represent samples from an extremely depleted mantle source. A large number of garnet inclusions have CaO contents of less than 1.8 wt.% and olivine inclusions are characterized by very high Mg-numbers (average: 94.6). These observations suggest that initial melt depletion in the protolith for the cratonic root beneath Kimberley (Kaapvaal Craton) exceeded orthopyroxene exhaustion (i.e. ≥ 50% melt extraction) and hence went farther than typically observed for cratonic peridotites worldwide. This signature of extreme depletion is not readily apparent from the study of mantle xenoliths from the same area and strongly underline..

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University of Melbourne Researchers