While mid-ocean ridge basalts provide wide-spread samples of the oceanic upper mantle and the chemistry of these rocks potentially constrains mantle temperature and composition, interpreting these constraints requires inversion using petrogenetic models that specify mangle mineralogy, temperature, geochemistry, and dynamics. Oxygen-isotope variations in these basalts have the potential to add important new constraints because oxygen-isotope composition of subducted oceanic crust differs from that of common mantle peridotites such that subduction of crust into the uppermantle can create domains that are both compositionally compositionally enriched in basaltic and sedimentary components and anomalous in delta 018. Detailed sutdies of suites selected to examine the influence of crystallization-differentiation, crustl assimilation, and sub-solidus alteration on the delta 018 of mid-ocean ridge basalts.
