Identification of Source Lithology in the Hawaiian and Canary Islands: Implications for Origins

Results are reported of an exploration of mantle source lithology for intraplate magmas using whole-rock and olivine phenocryst com-positions.This analysis includes modern mid-ocean ridge basalts and Archean komatiites as low- and high-temperature reference frames. It is shown that the Ni, Ca, Mn, and Fe/Mn contents of olivine pheno-crysts in modern mid-ocean ridge basalts and Archean komatiites are consistent with a normal peridotite source. In contrast, olivine pheno-crysts in shield-building lavas on Hawaii are higher in Ni and Fe/ Mn, and lower in Mn and Ca than those expected to crystallize from meltsofa normalperidotite source, andpoint to the importanceofpyrox-enite as proposed by Sobolev and co-workers. Hawaiian shield stage lavas and their olivine phenocrysts are similar to those expected from partial melts of a100 % stage 2 pyroxenite source. Such a source might form from a variety of melt^rock, melt^melt, and rock^rock reactions. Primary pyroxenite-derived magmas have a range of SiO2 contents