Ni isotopes provide a glimpse of Earth's pre-late-veneer mantle

• Published in: Science Advances
• Main Authors: Xu, Yong, Szilas, Kristoffer, Zhang, Lingyu, Zhu, Jian Ming, Wu, Guangliang, Zhang, Jie, Qin, Bin, Sun, Yao, Pearson, D. Graham, Liu, Jingao
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2023
• Subjects: Greenland; Narssaq
• Online Access: https://researchprofiles.ku.dk/da/publications/70e100a6-e8e7-4cdc-8a12-679b4725d31a; https://doi.org/10.1126/sciadv.adj2170; https://curis.ku.dk/ws/files/378756965/Ni_isotopes_provide_a_glimpse_of_Earth_s_pre_late_veneer_mantle.pdf

Moderately siderophile (e.g., Ni) and highly siderophile elements (HSEs) in the bulk silicate Earth (BSE) are believed to be partly or near-completely delivered by late accretion after the depletion caused by metallic core formation. However, the extent and rate of remixing of late-accreted materials that equilibrated with Earth's pre-late-veneer mantle have long been debated. Observing evidence of this siderophile element-depleted pre-late-veneer mantle would provide powerful confirmation of this model of early mantle evolution. We find that the mantle source of the ~3.8-billion-year-old (Ga) Narssaq ultramafic cumulates from Southwest Greenland exhibits a subtle 60Ni/58Ni excess of ~0.05 per mil and contains a clear HSE deficiency of ~60% relative to the BSE. The intermediate Ni isotopic composition and HSE abundances of the ~3.8-Ga Narssaq mantle mark a transitional Eoarchean snapshot as the poorly mixed 3.8-Ga mantle containing elements of pre-late-veneer mantle material transitions to modern Earth's mantle.