Uranium-Potassium relationship and apatite fission-track ages for a differentiated leucitite suite from New South Wales (Australia)

Abstract

Detailed analysis of the U-content and distribution in a differentiated leucitite suite shows that U is negatively correlated with K and decreases with increasing differentiation. It is found that U is preferentially concentrated in the late-crystallized fractions of the lavas, but the U concentrations decrease with increasing proportions of these fractions in the bulk rocks. Perovskite strongly partitions U from the differentiated liquid and reverses the U-enrichment trend calculated from crystal fractionation models. This process may be important in other perovskite-bearing alkalic lavas in the East African Rift, Hawaiian and Roman volcanic provinces. The lavas discussed are related to an ..