Heterogeneous nickel isotopic compositions in the terrestrial mantle – Part 1: Ultramafic lithologies

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

“…Lack of clear relationships between δ 60/58 Ni values and Ni contents and olivine core Mg# indicate limited Ni isotopic fractionation during igneous processes on the UPB. This is consistent with the fact that igneous processes do not effectively fractionate Ni stable isotopes on Earth, as evidenced by the absence of δ 60/58 Ni variations between peridotites (0.10 ± 0.07‰) and basalts (0.03 ± 0.16‰) (Klaver et al, 2020;Saunders et al, 2020Saunders et al, , 2021Wang et al, 2021). However, the variation of Mg# of ureilites may result from a mixing process, based on C, 54 Cr, and noble gas isotope evidence (Barrat et al, 2017;Broadley et al, 2020;Zhu, Moynier, Schiller, Wielandt, et al, 2020) Note.…”

“…Hence, Ni stable isotopes may be robust to trace planetary core formation by comparison between the compositions of planetary silicate fractions and chondrites that are taken as chemical proxies for bulk Earth and other terrestrial planets (Allègre et al., 1995), considering that the actual samples from the core are not accessible. Previous studies have comprehensively and systematically investigated the Ni stable isotope composition (expressed as δ 60/58 Ni, mass‐dependent per mil deviation of Ni 60 /Ni 58 ratios relative to NIST SRM 986) of chondrites with an average δ 60/58 Ni value of 0.23 ± 0.14‰ (2SD; Figure S1 in Supporting Information ) (Cameron et al., 2009; Chernonozhkin et al., 2016; Gall et al., 2017; Klaver et al., 2020; Moynier et al., 2007; Wang et al., 2021) and of the bulk silicate Earth (BSE) with an average δ 60/58 Ni value of 0.10 ± 0.07‰ (2SD) (Gall et al., 2017; Gueguen & Rouxel, 2021; Klaver et al., 2020; Saunders et al., 2020; Wang et al., 2021). Klaver et al.…”

“…Figure S1 in Supporting Information S1) (Cameron et al, 2009;Chernonozhkin et al, 2016;Gall et al, 2017;Klaver et al, 2020;Moynier et al, 2007;Wang et al, 2021) and of the bulk silicate Earth (BSE) with an average δ 60/58 Ni value of 0.10 ± 0.07‰ (2SD) (Gall et al, 2017;Gueguen & Rouxel, 2021;Klaver et al, 2020;Saunders et al, 2020;Wang et al, 2021). Klaver et al (2020) first observed the Ni isotope difference between chondrites and BSE, that is, Δ 60/58 Ni Chondrites-BSE = ∼0.13‰, and interpreted it by terrestrial core formation.…”

Sulfide Dissolution on the Nickel Isotopic Composition of Basaltic Rocks

“…The Ni isotopic differences between olivine and orthopyroxene, and between olivine and spinel in Beiyan peridotites, in general, agree with the predictions from the ionic model in this study, indicating equilibrium inter‐mineral Ni isotope fractionations. Figures 5a and 5b summarize all reported Ni isotopic data of coexisting olivine, orthopyroxene and/or spinel in δ – δ plots (Gall et al., 2017; Saunders et al., 2020). Orthopyroxene‐olivine pairs from Saunders et al.…”

“…Additionally, some anomalous Ni isotopic values observed in metasomatized peridotites are likely caused by mantle metasomatism (Klaver et al., 2020; Wang et al., 2021). This is supported by the fact that metasomatized peridotites have clinopyroxenes with large heterogeneity of δ 60/58 Ni (from −0.08‰ to +2.83‰), whereas olivine and orthopyroxene that dominate >90% of Ni budget in peridotites have similar Ni isotopic compositions to the bulk‐rock value (Gall et al., 2017; Klaver et al., 2020; Saunders et al., 2020). Recently, Saunders et al.…”