¹Cuiping Wang, ²Haolan Tang, ³ Miao, ² Yu, ¹ He, ^1,4 Liu, ²Fang Huang, ⁵Frederic Moynier, Jingao Liu
Earth and Planetary Science Letters 674, 119747 Link to Article [https://doi.org/10.1016/j.epsl.2025.119747]
¹State Key Laboratory of Geological Processes and Mineral Resources, and Frontiers Science Center for Deep-time Digital Earth, China University of Geosciences, Beijing 100083, China
²National Key Laboratory of Deep Space Exploration/State Key Laboratory of Lithospheric and Environmental Coevolution, University of Science and Technology of China, Hefei 230026, China
³Institution of Meteorites and Planetary Materials Research, Key Laboratory of Planetary Geological Evolution, Guilin University of Technology, Guilin 541006, China
⁴Key Laboratory of Earth and Planetary Physics, Chinese Academy of Sciences, CNRS, Beijing, China
⁵Université Paris cité, Institut de Physique du Globe de Paris, Paris 75005, France
Copyright Elsevier

Primitive differentiated meteorites serve as key messengers to reveal the formation and evolution of planetesimals in the early solar system. Ureilites, a group of achondritic meteorites, are interpreted as remnants of a disrupted asteroid’s residual mantle, yet the accretion location of their parent body remains uncertain. Here we report that ureilites exhibit distinct Mg and Si isotopic compositions, characterized by heavy Mg isotope (δ26Mg = -0.22 ‰ ± 0.01) and light Si isotope (δ30Si =-0.50 ‰ ± 0.02) compositions relative to ordinary and carbonaceous chondrites (δ26MgOC&CC:0.27 ‰ ± 0.01, δ30SiOC&CC:0.44 ‰ ± 0.01). Following an assessment of pressure and redox conditions on Si isotopic fractionation between silicate and metal, we propose that the subchondritic δ30Si signature of ureilites reflects the accretion of the ureilite parent body (UPB) occurred in an extremely reduced environment. The suprachondritic δ²⁶Mg signatures are attributed to evaporation processes from the UPB precursors during early accretionary stages. To constrain the precursors of the UPB, we conducted numerical simulations of Si-Mg isotopic variations in chondritic planetesimals under early nebular conditions, incorporating vapor loss. Results indicate that the UPB precursors possessed a Si isotope composition similar to enstatite chondrites. Collectively, we conclude that the UPB accreted proximal to the reservoirs of enstatite chondrites in the inner solar system under reduced conditions, and the UPB’s precursors had experienced silicon and magnesium loss via magma ocean evaporation.