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TimeTitle
1:00 PMGeochemistry Seminar: Edwin Schauble - Cerium and europium isotope fractionation
Description

Speaker: Edwin Schauble
Affiliation: UCLA, EPSS

Abstract:
Rare earth element abundances have been used to gain key insights into the origin and evolution of silicate melts on the Earth and other planetary bodies. It is now possible to measure natural, non-radiogenic variations in the isotopic compositions of many of these elements, but it’s not clear what controls them. This project aims to estimate equilibrium isotope fractionation in rare earth elements theoretically, which is a challenging problem because both mass dependent and mass independent effects are important. The two redox-sensitive REEs, cerium and europium, are contrasting examples. In the case of Ce(IV) vs. Ce(III), the relative importance of mass-dependent vs. mass-independent fractionation – and even the direction of fractionation – is predicted to be strongly dependent on the isotope pair measured. In the case of europium, mass-independent fractionation is dominant. Eu(II)-bearing species such as plagioclase are predicted to have higher 153Eu/151Eu than Eu(III)-bearing species by ~0.2-0.3‰ at magmatic temperatures, which is in qualitative agreement with recent measurements.

Submitted by: Omar Abuassaf (oabuassaf@epss.ucla.edu)