Observational Constraints on Melt-Rock Reactions during Melting of the Upper Mantle

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Recent work has indicated that dunite bodies in ophiolites, and presumably also in layered ocean crust, represent melt transport conduits through which basaltic melt has migrated and interacted chemically. In this proposal, Lundstrom proposes to test two aspects of this general hypothesis. First, he proposes to test the hypothesis that the melts that moved through the dunites are in fact very enriched and produced by melting of mafic heterogenieties in the mantle. He proposes to do this by measuring the isotopic compositions of oxygen and lithium in mantle spinels from ophiolite samples and mantle xenoliths. A second test, using samples from the Trinity ophiolite, is to determine whether there exist gradients in lithium and other incompatible element isotopes as a function of distance from dunite bodies.