Nickel and Chromium Stable Isotopic Composition of Ureilites: Implications for the Earth's Core Formation and Differentiation of the Ureilite Parent Body

We report the first Ni and Cr stable isotope data for ureilite meteorites that are mantle residue of a carbon-rich differentiated planet. Ureilites have similar compositions as chondrites, suggesting core-mantle differentiation parent body (UPB) did not fractionate isotopes. Since size Earth is potentially larger than UPB; with diameter >690 km), resulting in higher temperatures at boundary Earth, it can be predicted terrestrial core formation may directly cause fractionation. On other hand, we also high-precision composition ureilites, including one ureilitic trachyandesite (ALM-A) enriched lighter isotopes relative to main-group which suggests partial melting occurred on UPB. The globally heavy UPB compared chondrites caused by sulfur-rich processes.