Enriched mantle: Nd and Sr isotopes in diopsides from kimberlite nodules

Abstract

Nd and Sr isotope compositions of diopsides from micaceous garnet Iherzolite nodules found in kimberlite pipes at Bultfontein and Kimberley, South Africa are reported. The diopside data extend the mantle array, as defined by uncontaminated oceanic and continental basalts, to radiogenic 87Sr/86Sr values. These data are used to demonstrate the ancient enriched, grossly heterogeneous nature of the sub-continental mantle, which complements the predominantly depleted nature of the sub-oceanic mantle.