title: Heterogeneity in mantle carbon content from CO2-undersaturated basalts.
abstract: The amount of carbon present in Earth's mantle affects the dynamics of melting, volcanic eruption style and the evolution of Earth's atmosphere via planetary outgassing. Mantle carbon concentrations are difficult to quantify because most magmas are strongly degassed upon eruption. Here we report undegassed carbon concentrations from a new set of olivine-hosted melt inclusions from the Mid-Atlantic Ridge. We use the correlations of CO2with trace elements to define an average carbon abundance for the upper mantle. Our results indicate that the upper mantle carbon content is highly heterogeneous, varying by almost two orders of magnitude globally, with the potential to produce large geographic variations in melt fraction below the volatile-free solidus. Such heterogeneity will manifest as variations in the depths at which melt becomes interconnected and detectable, the CO2fluxes at mid-ocean ridges, the depth of the lithosphere-asthenosphere boundary, and mantle conductivity.
authors.affiliation: Carnegie Institution of Washington, Department of Terrestrial Magnetism, 5241 Broad Branch Road NW, Washington, District Of Columbia 20015-1304, USA.
authors.forename: M
authors.initials: M
authors.lastname: Le Voyer
authors.affiliation: Graduate School of Oceanography, University of Rhode Island, Narragansett Bay Campus, Narragansett Rhode Island 02882, USA.
authors.forename: K A
authors.initials: KA
authors.lastname: Kelley
authors.affiliation: Smithsonian Institution, National Museum of Natural History, PO Box 37012, MRC 119, Washington, District Of Columbia 20013-7012, USA.
authors.forename: E
authors.initials: E
authors.lastname: Cottrell
authors.affiliation: Carnegie Institution of Washington, Department of Terrestrial Magnetism, 5241 Broad Branch Road NW, Washington, District Of Columbia 20015-1304, USA.
authors.forename: E H
authors.initials: EH
authors.lastname: Hauri