title: Melting of subducted basalt at the core-mantle boundary.
abstract: The geological materials in Earth's lowermost mantle control the characteristics and interpretation of seismic ultra-low velocity zones at the base of the core-mantle boundary. Partial melting of the bulk lower mantle is often advocated as the cause, but this does not explain the nonubiquitous character of these regional seismic features. We explored the melting properties of mid-oceanic ridge basalt (MORB), which can reach the lowermost mantle after subduction of oceanic crust. At a pressure representative of the core-mantle boundary (135 gigapascals), the onset of melting occurs at ~3800 kelvin, which is ~350 kelvin below the mantle solidus. The SiO2-rich liquid generated either remains trapped in the MORB material or solidifies after reacting with the surrounding MgO-rich mantle, remixing subducted MORB with the lowermost mantle.
authors.affiliation: Laboratoire Magmas et Volcans, Université Blaise Pascal, CNRS, IRD, Clermont-Ferrand, France. denis.andrault@univ-bpclermont.fr.
authors.forename: Denis
authors.initials: D
authors.lastname: Andrault
authors.affiliation: Laboratoire Magmas et Volcans, Université Blaise Pascal, CNRS, IRD, Clermont-Ferrand, France.
authors.forename: Giacomo
authors.initials: G
authors.lastname: Pesce
authors.affiliation: Laboratoire Magmas et Volcans, Université Blaise Pascal, CNRS, IRD, Clermont-Ferrand, France.
authors.forename: Mohamed Ali
authors.initials: MA
authors.lastname: Bouhifd
authors.affiliation: Laboratoire Magmas et Volcans, Université Blaise Pascal, CNRS, IRD, Clermont-Ferrand, France.
authors.forename: Nathalie
authors.initials: N
authors.lastname: Bolfan-Casanova
authors.affiliation: Laboratoire Magmas et Volcans, Université Blaise Pascal, CNRS, IRD, Clermont-Ferrand, France.
authors.forename: Jean-Marc
authors.initials: JM
authors.lastname: Hénot
authors.affiliation: European Synchrotron Radiation Facility, Grenoble, France.
authors.forename: Mohamed
authors.initials: M
authors.lastname: Mezouar