9628142 Stolper Oxygen isotope ratios can provide important constraint on the origins of chemical and isotopic heterogeneity in the mantle sources of basaltic lavas. Conventional measurements of whole-rock specimens and glasses are typically significantly influenced by the effect of sample alteration and isotopic fractionation during magmatic processes. The P.I.s propose to use laser fluorination techniques to undertake a comprehensive survey of oxygen isotope variations in phenocrysts (primarily olivine) from arc-related lavas. Results thus far indicate that laser fluorination technique provides an accurate and precise means of analyzing 18O/16O ratios in olivine and other phenocrysts. The work will involve a survey of arc-related lavas, emphasizing basaltic back-arc lavas that can provide information on the mantle "wedge" above subduction zones.
