Isotopic Studies of Pacific Seamounts and Selected Ridge Segments

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A primary emphasis in the study of oceanic crustal rocks has been to develop a quantitative geochemical characterization of the upper mantle. Such information is important in understanding both the sources and processes which lead to the formation of the oceanic crust. Additionally, the geochemistry of the upper mantle and its homogeneity/heterogeneity place important constaints on models for convection of the mantle and evolution of the planet earth. The objective of the present award is to continue studies of the lead, strontium, and neodynium isotope composition of basalts dredged from Pacific ocean seamounts. Initial work on this project has been important im documenting the source of magmas to seamounts on the East Pacific Rise and to "hot spot" produced seamount chains in the western Pacific. Work to be supported during the next two years will include: 1)continued analysis of samples from the western Pacific, 2)initiation of studies on samples from the Hawiian Ridge,and 3)analysis of samples from seamounts near fracture zones. The principlal investigators are highly qualified to undertake the proposed study.