Origin of mass-independent oxygen isotope variation among ureilites: Clues from chondrites and primitive achondrites

Abstract

Ureilite meteorites are abundant, carbon-rich, primitive achondrites made of coarse-grained, equilibrated olivine and pyroxene (usually pigeonite). They probably sample the baked, heterogeneous, melt-depleted mantle of a large, once-chondritic parent body that was broken up catastrophically while still young and hot. Heterogeneity in the parent body is inferred from a considerable “slope-1” variation from one meteorite to another in oxygen isotopes (−2.5‰ < Δ17O