9315698 Hauri This new proposal will apply detailed textural, thermobarometry, ion microprobe, and Sr-Nd-Pb and Os isotopic analyses to suites of ultramafic xenoliths hosted by alkali basalts on the oceanic islands of Savai'i (Western Samoa), Tubuai (Austral Islands), Tahiti and Tahaa (Society Islands), Hiva Oa, Ua Huka and Nuka Hiva (Marquesas Islands), Oahu (Hawaiian Islands) and Aitutaki (Cook Islands). The relationship of these xenolith suites to volcanism at these islands will be examined by undertaking Sr, Nd, Pb and Os isotopic studies of stratigraphically controlled basalt sections from Tubuai, Oahu (Koolau and Honolulu Volcanics) Mauna Loa, and Tahaa. We propose extensive use of Os isotopes as tracers of compatible elements in peridotites and mantle-derived magmas in order to distinguish melt interaction with lithospheric versus plume derived mantle sources. Research will focus on specific issues such as: 1) mantle plume versus lithospheric origin for OIB-hosted xenoliths, 2) contribution of the oceanic lithosphere sources to isotopic variations in oceanic island basalts, 3) contrasting styles and products of magma-mantle beneath individual islands, as a function of lithospheric age, thickness, and temperature, and 4) the extent to which the physical and chemical characteristics of magma migration are controlled by variations in texture and grain size of the mantle.
