The Fe and Zn isotope composition of deep mantle source regions: Insights from Baffin Island picrites ...

• Main Authors: McCoy-West, AJ, Fitton, JG, Pons, ML, Inglis, EC, Williams, HM
• Format: Article in Journal/Newspaper
• Language: English
• Published: Elsevier BV 2018
• Subjects: Iron; Zinc; Stable isotopes; Picrites; Komatiites; Olivine; Sulfide; Baffin Island; Canada; Baffin; North Atlantic
• Online Access: https://dx.doi.org/10.17863/cam.27977; https://www.repository.cam.ac.uk/handle/1810/280611

Young (61 Ma) unaltered picrites from Baffin Island, northwest Canada, possess some of the highest 3He/4He (up to 50 Ra) seen on Earth, and provide a unique opportunity to study primordial mantle that has escaped subsequent chemical modification. These high-degree partial melts also record anomalously high 182W/184W ratios, but their Sr-Nd-Hf-Pb isotopic compositons (including 142Nd) are indistinguishable from those of North Atlantic mid-ocean ridge basalts. New high precision Fe and Zn stable isotope analyses of Baffin Island picrites show limited variability with δ56Fe ranging from −0.03‰ to 0.13‰ and δ66Zn varying from 0.18‰ to 0.28‰. However, a clear inflection is seen in both sets of isotope data around the composition of the parental melt (MgO = 21 wt %; δ56Fe = 0.08 ± 0.04‰; and δ66Zn = 0.24 ± 0.03‰), with two diverging trends interpreted to reflect the crystallisation of olivine and spinel in low-MgO samples and the accumulation of olivine at higher MgO. Olivine mineral separates are significantly ...