Evidence for primordial water in Earth’s deep mantle

Lydia J. Hallis, Gary R. Huss, Kazuhide Nagashima, G. Jeffrey Taylor, Sæmundur A. Halldórsson, David R. Hilton, Michael J. Mottl, Karen J. Meech

Science 13 November 2015:
Vol. 350 no. 6262 pp. 795-797
DOI: 10.1126/science.aac4834


“The hydrogen-isotope [deuterium/hydrogen (D/H)] ratio of Earth can be used to constrain the origin of its water. However, the most accessible reservoir, Earth’s oceans, may no longer represent the original (primordial) D/H ratio, owing to changes caused by water cycling between the surface and the interior. Thus, a reservoir completely isolated from surface processes is required to define Earth’s original D/H signature. Here we present data for Baffin Island and Icelandic lavas, which suggest that the deep mantle has a low D/H ratio (δD more negative than –218 per mil). Such strongly negative values indicate the existence of a component within Earth’s interior that inherited its D/H ratio directly from the protosolar nebula. “