Trace element abundances of high - MgO glasses from Kilauea

We performed an ion-microprobe study of eleven high-MgO (6.7±14.8 wt%) tholeiite glasses from the Hawaiian volcanoes Kilauea, Mauna Loa and Ha-leakala. We determined the rare earth (RE), high ®eld strength, and other selected trace element abundances of these glasses, and used the data to establish their relationship to typical Hawaiian shield tholeiite and to infer characteristics of their source. The glasses have trace element abundance characteristics generally similar to those of typical shield tholeiites, e.g. L(light)REE/ H(heavy)REE C1 b 1. The Kilauea and Mauna Loa glasses, however, display trace and major element characteristics that cross geochemical discriminants observed between Kilauea and Mauna Loa shield lavas. The glasses contain a blend of these discriminating chemical characteristics, and are not exactly like the typical shield lavas from either volcano. The production of these hybrid magmas likely requires a complexly zoned source, rather than two unique sources. When corrected for olivine fractionation, the glass data show correlations between CaO concentration and incompatible trace element abundances, indicating that CaO may behave incompatibly during melting of the tholeiite source. Furthermore, the tholeiite source must contain residual garnet and clinopyroxene to account for the variation in trace element abundances of the Kilauea glasses. Inversion modeling indicates that the Kilauea source is ¯at relative to C1 chondrites, and has a higher bulk distribution coecient for the HREE than the LREE.