The Lithosphere-Asthenosphere Boundary

Fischer, Karen M., Ford, Heather A., Abt, David L. and Rychert, Catherine A. (2010) The Lithosphere-Asthenosphere Boundary. Annual Review of Earth and Planetary Sciences, 38 (1), 551-575. (doi:10.1146/annurev-earth-040809-152438).

Record type: Article

Abstract

Seismological models of upper-mantle structure are providing new constraints on the physical and chemical properties that differentiate the lithosphere from the asthenosphere. A wide variety of studies are consistent with an oceanic lithosphere that corresponds to a dry, chemically depleted layer over a hydrated, fertile asthenosphere. At the lithosphere-asthenosphere boundary beneath oceans and many Phanerozoic continental regions, observed seismic velocity gradients require a contrast in mantle hydration, fertility, and/or melt content, perhaps in combination with a vertical gradient in velocity anisotropy. Beneath cratons, evidence is growing for a deeper—but globally ubiquitous—asthenosphere. Some studies conclude that the cratonic lithosphere-asthenosphere boundary is gradual enough to be matched by a purely thermal gradient, whereas others indicate a more rapid transition and a contrast in composition or perhaps melt content.

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