Diamonds from the Murowa Kimberlites: Formation Within Extremely Depleted and Metasomatized Zimbabwean Peridotitic Subcontinental Mantle

Murowa kimberlites are situated in the 3.5 Ga Tokwe block, the oldest part of the Zimbabwe craton. The diamonds are predominantly white or pale brown octahedra of high gem quality. Mineral inclusions are overwhelmingly peridotitic, dominated by chromite, sulfide, and olivine, with only minor amounts of orthopyroxene and garnet, suggestive of a very depleted lithospheric peridotite mantle host. Carbon isotope values for the diamonds range from δ13C –5.8 to –2.5‰ and are consistent with global peridotitic diamond signatures. Diamonds with an eclogitic paragenesis are virtually absent.