Heterogeneity in mantle carbon content from CO2-undersaturated basalts

• Published in: Nature communications Vol. 8; no. 1; p. 14062
• Main Authors: Le Voyer, M., Kelley, K.A., Cottrell, E., Hauri, E.H.
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 13-01-2017; Nature Publishing Group; Nature Portfolio
• Subjects: 704/2151/209; 704/2151/431; 704/2151/598; Carbon; Crystallization; Humanities and Social Sciences; multidisciplinary; Science; Science (multidisciplinary); Trace elements; United States > US; Mid-Atlantic Ridge
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/ncomms14062

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 CO
2
with 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 CO
2
fluxes at mid-ocean ridges, the depth of the lithosphere-asthenosphere boundary, and mantle conductivity.
Melting dynamics are affected by the amount of carbon in the Earth’s mantle. Le Voyer
et al
. report undegassed carbon concentrations from olivine-hosted melt inclusions from the Mid-Atlantic Ridge finding that carbon content varies by two orders of magnitude thus introducing heterogeneity into the upper mantle.