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

Ke Zhu , Jean-Alix Barrat (1, 2) , Akira Yamaguchi , Olivier Rouxel (3) , Yoan Germain (3) , Jessica Langlade , Frederic Moynier (4)

1 IUF - Institut universitaire de France
2 LEMAR - Laboratoire des Sciences de l'Environnement Marin (LEMAR)
3 LGO - Laboratoire Géosciences Océan
4 IPGP (UMR_7154) - Institut de Physique du Globe de Paris

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

Mots clés: ureilites; Ni stable isotopes; Cr stable isotopes; core formation; partial melting; mantle heterogeneity

Domaines: Planète et Univers [physics]

Ke Zhu, Jean-Alix Barrat, Akira Yamaguchi, Olivier Rouxel, Yoan Germain, et al.. Nickel and Chromium Stable Isotopic Composition of Ureilites: Implications for the Earth's Core Formation and Differentiation of the Ureilite Parent Body. Geophysical Research Letters, 2022, 49, ⟨10.1029/2021GL095557⟩. ⟨insu-03685884⟩