Chromite-silicate intergrowths in upper-mantle peridotites

Abstract

Magnesian chromite has been found in “fingerprint” intergrowths with olivine, orthopyroxene, clinopyroxene and amphibole in xenoliths of peridotite from various South African kimberlite diatremes. The composition of the minerals in the intergrowth is essentially the same as that for the minerals occurring throughout the rock, suggesting that the intergrowths are a crystallization phenomenon rather than the result of alteration or metasomatic replacement. A chromite-olivine intergrowth in a peridotite xenolith from the Lashaine volcano, Tanzania, is also described.