Collaborative Research: Experimental Determinations of Trace Element Distributions between Melts and Mantle Phases at P,T and X Relevant to MORB Genesis

Florida State University, Tallahassee FL

Investigators

Abstract

Recommended project is for three years of continued funding of research on coupled phase equilibria and trace element partitioning between mantle phases and melt at temperatures, pressures and compositions which closely approximate those which exist under mid-ocean ridges during partial mantle melting and mid-ocean ridge basalt (MORB) genesis. This work will build upon previous results that determined mineral-melt partitioning at for lherzolite mantle compositions at pressures between 1.2 and 3.4 Gpa. Crystal liquid partition coefficients will be determined for the rare earth elements (REE), Hf, Zr, Nb, U, Th, and Ba using an ion microprobe. Analytical charges will be prepared that are as close as possible to the peridotite solidus to most closely approximate conditions of partial mantle melting. In this work peridotite experimental charges formed at pressures up to 5.0 Gpa will be examined, including new studies at lower pressures. Pyroxenite charges representing pressures of 1.0-3.0 Gpa will also be analyzed, to form critical datasets that will allow the testing of models hypothesizing garnet pyroxenite (or eclogite) in the source of both MORB and plume melts. Depleted peridotite (harzburgite) charges will also be analyzed. These new data will be incorporated into new integrated models of mantle melting that integrate both major and trace element compositions. ***