EVIDENCE FOR HOTSPOT-RELATED CARBONATITE METASOMATISM IN THE OCEANIC UPPER-MANTLE

Four peridotite xenoliths from the islands of Savai'i (Western Samoa) and Tubuai (Austral Islands) contain primary olivine of lithospheric origin, and secondary assemblages of clinopyroxene + spinel +/- apatite. The trace-element contents of the secondary minerals show that they formed in equilibrium with carbonate-rich melts. Moreover, isotopic results indicate that these melts were derived from recycled crustal components in the convecting mantle, and place constraints on the origins of these components.