PB ISOTOPIC VARIABILITY IN MELT INCLUSIONS FROM OCEANIC ISLAND BASALTS, POLYNESIA

Previous studies have suggested that melting processes are responsible for the trace element variability observed in olivine-hosted basaltic melt inclusions. Melt inclusions from three individual lava samples ( two from Mangaia, Cook Islands, and one from Tahaa, Society Islands) h ave heterogeneous Pb isotopic compositions, even though the erupted La vas are isotopically homogeneous, The range of Pb isotopic composition s from individual melt inclusions spans 50 percent of the worldwide ra nge observed for ocean island basalts, The melt inclusion data can be explained by two-component mixing for each island. Our data imply that magmas with different isotopic compositions existed in the volcanic p lumbing system before or during melt aggregation.