Rio Grande Rift Crustal Boundaries

        1. 1.8–1.65-Ga contractional amalgamation of lithosphere in the southwestern United States produced major northeast-striking tectonic boundaries. Cheyenne belt = Archean–Proterozoic suture; Gneiss Canyon to Crystal shear zones = distributed boundary between Mojave and Yavapai provinces; Yavapai–Mazatzal transition is marked at its northern edge by a northern limit of 1.65-Ga deformation; at its southern edge by the south limit of pre–1.7-Ga Yavapai province crust. Dot pattern shows areas of 1.7-Ga mature quartzite deposition; triangles are areas of 1.7-Ga rhyolitic calderas; stars show locations and dates of late synorogenic granitoids. Teeth indicate vergence(s) of contractional deformation. Precambrian rock outcrops are delineated in dark gray, and the Colorado Plateau is shown in light gray. (Caption and figure from Karlstrom and Humphreys, 1998)
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