1. Department of Earth Sciences, University of Manchester, Oxford Road, Manchester M13 9LP, UK
2. Centre de Recherches Pétrographiques et Géochimiques, 15 Rue Notre Dame des Pauvres, BP 20, and
3. Ecole Nationale Supérieure de Géologie, Rue du Doyen Roubault, 54501 Vandoeuvre lès Nancy Cedex, France
4. Department of Geology, University of Toronto, 22 Russell Street, Toronto, Ontario M5S 3B1, Canada
5. Department of Geosciences, University of Houston, Houston, Texas 77204-5503, USA

Correspondence to: Chris J. Ballentine¹ Correspondence and requests for materials should be addressed to C.J.B. (Email: chris.ballentine@manchester.ac.uk).

Abstract

Identifying the origin of primordial volatiles in the Earth's mantle provides a critical test between models that advocate magma-ocean equilibration with an early massive solar-nebula atmosphere and those that require subduction of volatiles implanted in late accreting material. Here we show that neon isotopes in the convecting mantle, resolved in magmatic CO₂ well gases, are consistent with a volatile source related to solar corpuscular irradiation of accreting material. This contrasts with recent results that indicated a solar-nebula origin for neon in mantle plume material, which is thought to be sampling the deep mantle. Neon isotope heterogeneity in different mantle sources suggests that models in which the plume source supplies the convecting mantle with its volatile inventory require revision. Although higher than accepted noble gas concentrations in the convecting mantle may reduce the need for a deep mantle volatile flux, any such flux must be dominated by the neon (and helium) isotopic signature of late accreting material.

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