A Comparative Elemental and Isotopic Study of Seawater Component Assimilation on the East Pacific Rise (EPR) Using Volatiles, Halogens, Boron and Lithium

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An ion microprobe (secondary ion mass spectrometer) study of the halogens (Cl, F), volatiles (CO2, H2O, S), light elements (B, Li) and their relevant isotopic compositions (7Li/6Li, 11B/10B, 34S/32S and 37Cl/35Cl) will be carried out on well-characterized East Pacific Rise (EPR) glasses from the 9 degrees N, 12 degrees N, and 15-16degrees N regions. Assimilation of seawater components into basaltic magma along the global ocean ridge system may be more widespread than is commonly assumed. At fast-spreading ridges such as the EPR where axial magma chambers are well-defined, this process may be ubiquitous. There is currently a poor understanding of the seawater-component assimilation process on the local spatial scale of volcanic features and petrologic segmentation. This work will use different geochemical tools, each with its own response to the assimilation process and look at segments of the ridge system where small differences in spreading rate, volcanic edifice, lithospheric structure and axial magma chamber morphology can be recognized. The purpose of this study is to determine how and where seawater component assimilation occurs in the oceanic lithosphere, to relate differences in the extent of this process to volcanic and morphologic features of the oceanic ridge system.