NORTH AMERICAN OPHIOLITES AND SUTURES: ANALOGUES WITH SW PACIFIC AND ALPINE-MEDITERRANEAN BELTS

Ophiolites are formed at oceanic spreading centers and emplaced principally by collision of a continental or island arc crustal margin with a subduction zone dipping away from it. Nonaccretionary subduction zones recycle old oceanic lithosphere, including sediments, into the mantle to be recycled as new suprasubduction-like oceanic crust.

Western North American ophiolites may form as in the western Pacific--complex intra-arc rifting and closure (e.g. Philiippines: Encarnacion, 2004) or multiple rifting, sutures, collisions, rapid plate margin changes, and extensive transform faulting (e.g., Indonesia-Philiippines: Hall and Wilson, 2000). Alpine-Mediterranean nappes, sutures, ophiolites, thrust-belt and subduction parallism, collisions, and subduction polarity flips also provide insight into Cordilleran tectonic events.

In northern California-western Nevada, possible sutures--some involving westward subduction--include the following boundaries: 1. Franciscan Coastal-Central belts; 2. Coast Range/Great Valley Ophiolite-Western Jurassic belt; 2. Western Jurassic Belt-Central Belt; 3. Central Belt-Feather River Peridotite; 4. Feather River Peridotite--"Cedar" rocks; 5. "Cedar" rocks-Eastern Belt. Also, 6. Pre-380 Ma serpentinite-Shoo Fly contact; 7. Intra Jurassic-Cretaceous oceanic-continental volcanic rock boundary; and 8. A late Mesozoic suture between the Philippine-like northern Sierra Nevada and the ribbon continent "Rubia" (Hildebrand, 2009, 2013). Some sutures may continue into the southern Sierra-Nevada; they may also be loci of younger major strike-slip faults. Contemporaneous regions north and south show broadly similar relations. Irving, et al. were right 40 years ago about northward movement of the Canadian Cordillera. Any traces of the 80-60 Ma northward migration of Wrangellia-Stikinia past California will be found between the Franciscan Coastal and Central Belts. Smartville ophiolite and younger topographically higher pluton surfaces model the southern San Joaquin sub-basement.