MINERAL-AQUEOUS FLUID PARTITIONING OF TRACE ELEMENTS AT 900-1200°C AND 3.0-5.7 GPA: NEW EXPERIMENTAL DATA FOR GARNET, CLINOPYROXENE, AND RUTILE, AND IMPLICATIONS FOR MANTLE METASOMATISM

Abstract

In order to constrain the role of fluid phases during metasomatic processes in the upper mantle, trace element partition coefficients for Ba, Sr, Pb, Nb, Ta, Zr, Hf, Ti, La, Ce, Sm, Tb, and Yb between aqueous fluids and eclogite assemblage minerals (garnet, clinopyroxene, and rutile) have been determined experimentally at 900–1200°C and 3.0–5.7 GPa. Using a new experimental technique in which diamond aggregates are added to the experimental capsule set-up, the fluid was separated from the solid residue so that both quenched solute and residual minerals could be analysed directly. Trace element concentrations were determined in situ by laser ablation microprobe (LAM).