Partition of uranium and thorium between augite and host lavas

Abstract

Contents of U and Th in mineral fractions separated from some volcanic lavas and a peridotite nodule have been measured. Th U ratios were larger in the groundmass than in the augite phenocryst of the lava. In the peridotite nodule, U and Th were most enriched in diopside. Ionic substitution of Ca in clinopyroxene by U and Th under equilibrium conditions is proposed for the possible partition mechanism.