Margins: Experimental Investigation of Hydrous Peridotite Melting beneath Volcanic Arcs

Woods Hole Oceanographic Institution, Woods Hole MA

Investigators

Abstract

0112013 Gaetani The objectives of this project are (1) to determine the compositional characteristics and liquidus temperatures of hydrous partial melts formed through fluxing of mantle peridotite by a H2O-rich component from the subducted oceanic lithosphere, and (2) to measure mineral/melt partition coefficients appropriate for modeling trace element fractionations during partial melting of hydrous peridotite in the mantle wedge. These goals are being achieved by determining experimentally (1) the compositions of hydrous silicate melts in equilibrium with a lherzolite mineral assemblage at 2.0 to 3.0 GPa, (2) the effect on partial melting of adding variable amounts of a Na2O-K2O-H2O subduction component to the peridotite, and (3) the partitioning of incompatible trace elements between mantle minerals (clinopyroxene, garnet, amphibole) and hydrous partial melts at conditions appropriate for the mantle beneath volcanic arcs. The results from this experimental study will provide petrologic and geochemical data necessary for understanding the role of H2O in generating arc magmas and determining the composition of material transferred from the mantle to the crust by subduction-related magmatic processes. The results will also help to provide a framework for interpreting samples from MARGINS Focus Sites in the Izu-Bonin-Mariana and Central American subduction systems.