Chemistry and Physics of Minerals and Rocks/Volcanology
Lithospheric mantle duplex beneath the central Mojave Desert revealed by xenoliths from Dish Hill, California
Article first published online: 5 MAR 2009
Copyright 2009 by the American Geophysical Union.
Journal of Geophysical Research: Solid Earth (1978–2012)
Volume 114, Issue B3, March 2009
How to Cite
2009), Lithospheric mantle duplex beneath the central Mojave Desert revealed by xenoliths from Dish Hill, California, J. Geophys. Res., 114, B03202, doi:10.1029/2008JB005906., , , and (
- Issue published online: 5 MAR 2009
- Article first published online: 5 MAR 2009
- Manuscript Accepted: 12 DEC 2008
- Manuscript Revised: 30 NOV 2008
- Manuscript Received: 30 JUN 2008
 Low-angle subduction of oceanic lithosphere may be an important process in modifying continental lithosphere. A classic example is the underthrusting of the Farallon plate beneath North America during the Laramide orogeny. To assess the relevance of this process to the evolution and composition of continental lithosphere, the mantle stratigraphy beneath the Mojave Desert was constrained using ultramafic xenoliths hosted in Plio-Pleistocene cinder cones. Whole-rock chemistry, clinopyroxene trace element and Nd isotope data, in combination with geothermometry and surface heat flow, indicate kilometer-scale compositional layering. The shallow parts are depleted in radiogenic Nd (ɛNd = −13 to −6.4) and are interpreted to be ancient continental mantle that escaped tectonic erosion by low-angle subduction. The deeper samples are enriched in radiogenic Nd (ɛNd = +5.7 to +16.1) and reveal two superposed mantle slices of recent origin. Within each slice, compositions range from fertile lherzolites at the top to harzburgites at the bottom: the latter formed by 25–28% low-pressure melt depletion and the former formed by refertilization of harzburgites by mid-ocean-ridge-basalt-like liquids. The superposition and internal compositional zonation of the slices preclude recent fertilization by Cenozoic extension-related magmas. The above observations imply that the lower Mojavian lithosphere represents tectonically subcreted and imbricated lithosphere having an oceanic protolith. If so, the lherzolitic domains may be related to melting and refertilization beneath mid-ocean ridges. The present Mojavian lithosphere is thus a composite of a shallow section of the original North American lithosphere underlain by Farallon oceanic lithosphere accreted during low-angle subduction.