CONSTRAINTS ON CLINOPYROXENE/MELT PARTITIONING OF REE, RB, SR, TI, CR, ZR, AND NB DURING MANTLE MELTING: FIRST INSIGHTS FROM DIRECT PERIDOTITE MELTING EXPERIMENTS AT 1.0 GPA

Abstract

Earlier piston-cylinder experiments in our laboratory produced a collection of mantle melting run products at 1.0 GPa that have now been analyzed by ion probe for selected REE, Ti, Cr, Rb, Sr, Y, Zr, and Nb. Natural starting materials were used and experiments were run in graphite-lined Pt capsules with the melt separated from the residual minerals into a layer of vitreous carbon spheres (VCS) to circumvent quench modification. The glass phase in 18 run products, representing melt percentages of ∼2–20 wt%, yielded excellent data that were inverted to yield the first estimates ever of clinopyroxene/melt distribution coefficients, Ds, derived from direct peridotite partial melting experiments. Uncertainties were estimated with a Monte Carlo method.