title: Metasomatized lithosphere and the origin of alkaline lavas.
abstract: Recycled oceanic crust, with or without sediment, is often invoked as a source component of continental and oceanic alkaline magmas to account for their trace-element and isotopic characteristics. Alternatively, these features have been attributed to sources containing veined, metasomatized lithosphere. In melting experiments on natural amphibole-rich veins at 1.5 gigapascals, we found that partial melts of metasomatic veins can reproduce key major- and trace-element features of oceanic and continental alkaline magmas. Moreover, experiments with hornblendite plus lherzolite showed that reaction of melts of amphibole-rich veins with surrounding lherzolite can explain observed compositional trends from nephelinites to alkali olivine basalts. We conclude that melting of metasomatized lithosphere is a viable alternative to models of alkaline basalt formation by melting of recycled oceanic crust with or without sediment.
authors.affiliation: Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA 91125, USA. sebastien.pilet@unil.ch
authors.forename: Sébastien
authors.initials: S
authors.lastname: Pilet
authors.forename: Michael B
authors.initials: MB
authors.lastname: Baker
authors.forename: Edward M
authors.initials: EM
authors.lastname: Stolper