26Al-26Mg Chronometry of the Northwest Africa 10463 Angrite: Implications for Differentiation Timescales on Planetesimals in the Early Solar System

This report is on an investigation of the 26Al-26Mg isotope systematics in the NWA 10463 angrite to constrain the timing of formation of this achondrite on its parent body. The analyses of the whole rock and mineral separates of olivine, pyroxene, and plagioclase were performed using multi-collector inductively coupled plasma mass spectrometry. From the isotope systematics, no evidence of live 26Al could be resolved, but an upper limit on the 26Al/27Al ratio of <1.6 x 10-8 was estimated. This upper limit corresponds to a model age of <4560.1 Ma, which is significantly younger than the crystallization ages of the volcanic angrite ages of ~4563-4564 Ma, but is consistent with the plutonic angrite ages of ~4557-4558 Ma.