This study will focus primarily on the detailed geochemistry of the Society Island chain in collaboration with geological, geochronological and petrological studies being carried on at Oregon State University and in France. This continuing study will determine geochemical variations related to volcanic evolution, and will attempt to verify the existance of a geographic isotopic pattern suggested by reconnaissance data, making it possible to test specific models of plume dynamics and plume-lithosphere interactions. A detailed isptopic study of the island of Tahiti will be completed, and reconassance and xenolith studies will be conducted on the other islands. Two additional activities will also be pursued. The first is a study of Pb/Ce ratios from Samoa to test whether the Samoan post erosional source contains a recycled component. The second will be an attempt to demonstrate the potential benefits of mass spectrometric determination of Th isotope ratios.
