Sr-Nd-Pb-Th Isotopic Composition of Lavas and Xenoliths Fromthe Canary Islands: Changes in Lithospheric Composition as a Function of Distance From the African Continent

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This proposal is to study the Sr-Nd-Pb-Th isotopic geochemistry of: (1) volcanics and plutonics from five of the Canary Islands and (2) peridotite xenoliths from Lanzarote, the easternmost island, and La Palma, the second westernmost island. Preliminary Sr-Nd-Pb-Th isotope data from the westernmost islands and published data from the eastern islands suggest systematic variation in isotopic compositions as a function of distance from West Africa. It may be that these variations reflect interaction of plume melts with the lithospheric mantle, which changes from transitional continental-oceanic in the east (with an enriched mantle composition) to predominantly oceanic in the west (with a depleted mantle composition). The study has important implications for the location (lithosphere, asthenosphere, plume) of the various mantle components, and for the recycling of continental lithosphereic mantle during rifting.