Ultrapotassic Magmas along the Flanks of the Oligo-Miocene Rio Grande Rift, USA: Monitors of the Zone of Lithospheric Mantle Extension and Thinning Beneath a Continental Rift

Recent theoretical studies of rift tectonics have concluded that their observed geophysical features, require that (1) extension affects a much wider zone of the underlying lithospheric mantle than the crust; (2) early extension involves a comparatively wide zone that narrows with time. The Neogene evolution of the segment of the Rio Grande rift between the Great Plains and Colorado Plateau shows this theoretical pattern clearly. The width of …