Primordial neon in high-³He/â´He Baffin Island olivines

• Published in: Earth and Planetary Science Letters
• Main Authors: Horton, F., Curtice, J., Farley, K. A., Kurz, M. D., Asimow, P. D., Treffkorn, J., Boyes, X. M.
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: Elsevier 2021
• Subjects: primordial mantle; hotspot lavas; neon isotopes; noble gas geochemistry; Baffin Island; Canada; Nunavut; Baffin; Iceland; inuit
• Online Access: https://doi.org/10.1016/j.epsl.2021.116762

Paleocene basaltic lavas exposed on Baffin Island have the highest ³He/â´He found in any terrestrial igneous rocks and potentially contain the most pristine primordial mantle material exposed on Earth's surface. By vacuum-crushing large (1–3 g) olivine mineral separates, we extracted enough magmatic gas to obtain the first coupled helium, neon, and argon isotopic compositions of Baffin Island lavas. The five Baffin Island olivine samples have ³He/â´He ranging from 36.2 ± 0.6 to 48.6 ± 1.3 (1σ) times the atmospheric ratio (Ra), overlapping with the highest known mantle values. Neon isotopic results fall on a mixing line between atmosphere and a high ²â°Ne/²²Ne mantle endmember (with a maximum ²â°Ne/²²Ne of 12.2). The slope of this mixing line is indistinguishable from that in subglacial Holocene glass from Iceland, but distinct from other hotspots and mid-ocean ridge basalt trends. This result supports the hypothesis that Baffin Island and Iceland lavas share a common high-³He/â´He mantle component, despite the fact that recent paleogeographic reconstructions place the Iceland hotspot far from Baffin Island at the time of eruption (61 Ma). Our results also demonstrate that high-³He/â´He mantle reservoirs have ³He/²²Ne variability that either reflects ancient mantle heterogeneity or helium addition in the upper or lower mantle. © 2021 Elsevier B.V. Received 7 October 2020, Revised 11 December 2020, Accepted 11 January 2021, Available online 25 January 2021. The National Science Foundation (award #1911699) funded this research. The Woods Hole Oceanographic Institution (WHOI) Andrew W. Mellon Foundation Endowed Fund for Innovative Research and a National Geographic Society grant (#CP4-144R-18) supported fieldwork activities. The WHOI noble gas lab was supported by NSF OCE #1259218 and WHOI. We thank Maryse Mahy of the Parks Canada Nunavut Field Unit, the Qikiqtani Inuit Association, and the Nunavut Research Institute for their assistance and cooperation. Victoria Hooton provided invaluable help ...