Heterogeneous nickel isotope compositions of the terrestrial mantle – Part 2: Mafic lithologies ...

• Main Authors: Saunders, Naomi J., Barling, Jane, Harvey, Jason, Fitton, J. Godfrey, Halliday, Alexander N.
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: Columbia University 2021
• Subjects: Nickel; Basalt; Isotope geology; Geochemistry; FOS: Earth and related environmental sciences; Mid-Atlantic Ridge; Pacific; Iceland; Ocean Island
• Online Access: https://dx.doi.org/10.7916/d8-q6x0-t556; https://academiccommons.columbia.edu/doi/10.7916/d8-q6x0-t556

We report stable Ni isotope compositions (δ⁶⁰/⁵⁸Ni, relative to SRM986) for mafic lavas with a range of -0.16 ‰ to +0.20 ‰ (n=44), similar to that of peridotite samples. Ocean island basalts (OIB) have been analysed from Iceland (n=6), the Azores (n=3), the Galápagos Islands (n=2), and Lōʻihi, Hawaii (n=1). Samples from Iceland (average δ⁶⁰/⁵⁸Ni = +0.13±0.16‰, 2s, n=7) display the greatest range in Ni isotope compositions from a single OIB location in this work, of +0.01 ‰ to +0.23 ‰. Samples from the Azores (average δ⁶⁰/⁵⁸Ni = -0.10±0.10 ‰, 2s) and Galápagos (average δ⁶⁰/⁵⁸Ni = -0.01±0.04 ‰, 2s) are generally isotopically lighter. The single Lōʻihi sample has a δ⁶⁰/⁵⁸Ni of +0.17 ‰. The lightest analysed bulk rock δ⁶⁰/⁵⁸Ni in this work, -0.16 ‰, is from the Azores island, Pico. Enriched mid ocean ridge basalts (E-MORB), which have (La/Sm)_N>1, are isotopically lighter than normal type MORB (N-MORB), as shown by data from the Mid Atlantic Ridge (n=9) and East Pacific Rise (n=3). All E-MORB average δ60/58Ni ...