^1,2Ke Zhu, ³Martijn Klaver, ^4,5,6Wei-Biao Hsu, ⁷Harry Becker, ⁸Lu Chen, ⁹Qi Chen
Geochimica et Cosmochimica Acta (in Press) Open Access Link to Article [https://doi.org/10.1016/j.gca.2025.10.009]
¹Bristol Isotope Group, School of Earth Sciences, University of Bristol, Wills Memorial Building, Queen’s Road, Bristol BS8 1RJ, United Kingdom
²State Key Laboratory of Geological Processes and Mineral Resources, Hubei Key Laboratory of Planetary Geology and Deep-Space Exploration, School of Earth Sciences, China University of Geosciences, Wuhan 430074, China
³Institut für Mineralogie, Westfälische Wilhelms-Universität Münster, Corrensstraße 24, 48149 Münster, Germany
⁴CAS Center for Excellence in Comparative Planetology, Purple Mountain Observatory, Chinese Academy of Sciences, Nanjing 210023, China
⁵State Key Laboratory of Lunar and Planetary Sciences, Macau University of Science and Technology, Avenida Wai Long, Taipa, Macau
⁶School of Earth Sciences and Engineering, International Center for Isotope Effects Research, Nanjing University, Nanjing 210023, China
⁷Freie Universität Berlin, Institut für Geologische Wissenschaften, Malteserstr. 74-100, 12249 Berlin, Germany
⁸Wuhan SampleSolution Analytical Technology Co., Ltd, Wuhan, China
⁹Department of Earth Science & Environmental Change, University of Illinois at Urbana Champaign, Urbana, IL, United States
Copyright Elsevier

To understand accretion and differentiation of Mars, we report high-precision mass-dependent Ni (siderophile and chalcophile) isotope data of 37 bulk Martian meteorites. Large δ60/58Ni variations observed among these Martian meteorites are attributed primarily to magmatism and Ni diffusion in zoned olivine and sulfide. Shergottites show systematically higher Mg# and lower δ60/58Ni values relative to nakhlites, which can be caused by olivine crystallization, consistent with the Ni isotope fractionation factor between olivine and melt. Two Ni-rich chassignites (Martian dunites) provide the best current estimate of the upper limit of δ60/58Ni of bulk silicate Mars (BSM): 0.110 ± 0.031 ‰, since olivine crystallization causes Ni isotope fractionation. Subtracting a presumably chondritic contribution by late accretion, the proto-BSM should possess a δ60/58Ni of ≤ 0.074 ‰ that is lower than the average of chondrites (∼0.24 ‰). This sub-chondritic value of Martian mantle suggests the sulfur-rich core formation has not caused Ni isotope fractionation, because the sulfide and Martian sulfur-rich core is believed to enrich in light Ni isotopes. Instead, Ni isotope differences between Earth, Mars, Vesta, and the ureilites can be inherited from non-bulk chondritic precursor materials.