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Published May 16, 2008 | Supplemental Material
Journal Article Open

Metasomatized Lithosphere and the Origin of Alkaline Lavas


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.

Additional Information

© 2008 American Association for the Advancement of Science. Received 15 February 2008; accepted 2 April 2008. We thank S. Newman and A. Ulianov for their help during data acquisition by Fourier transform infrared spectroscopy and laser ablation inductively coupled plasma mass spectrometry, respectively, and B. Azambre and J. Hernandez for their help during sample collection. Supported by the Swiss National Science Foundation, the Société Académique Vaudoise, and NSF grant EAR-9528594.

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