Experimental actinide element partitioning between whitlockite, apatite, diopsidic clinopyroxene, and anhydrous melt at one atmosphere and 20 kilobars pressure

Fission and alpha track radiography techniques have been used to measure partition coefficients (D) at trace (ppM) concentration levels for the actinide elements Th, U, and Pu between synthetic diopsidic clinopyroxene, whitlockite (β-Ca3(PO4)2, apatite, and coexisting haplobasaltic silicate liquid at 1 bar and 20 kilobars pessure at oxygen fugacities from 10-86 to 10-07 bars. Equilibrium (Rayleigh) partitioning at the crystal-liquid interface is assumed, and corrections for actinide zoning and relative alpha and fission fragment ranges have been applied to the measured D values. Reproducibility for both actinide and minor element D values is carefully examined as a criterion for crystal-liquid interface equilibrium. The data are mostly compatible with interface equilibrium except at high cooling rates