Volcanic rock and mantle xenolith compositions in the Sierra Nevada (western United States) contradict a commonly held view that continental crust directly overlies asthenosphere beneath the Sierran range front, and that ancient continental mantle lit . . .

A long-standing issue in Cordilleran geology involves the nature of Basin and Range (western USA) volcanism, and whether such magmatism provides a trigger for extensional deformation, or if volcanic activity is a passive response to extension. We use . . .