THE JURASSIC ARC SILICIC LARGE IGNEOUS PROVINCE (SLIP) OF SOUTHWESTERN NORTH AMERICA

Rhyolite-dominated volcanic outpourings with eruptive volumes comparable to continental flood basalts and characterized by short duration high flux magmatic events are referred to as silicic large igneous provinces (SLIPs). The circumstances that trigger such events is still poorly understood but have been related to mantle plumes or shallower-sourced melting anomalies related to plate tectonics. Here, the ~2500-km-long Jurassic continental margin magmatic arc segment extending from eastern California to east-central Mexico is recognized as a subduction-related SLIP on the basis of its aerial extent, thick rhyolite ignimbrite-dominated volcanic/sedimentary sections, rapid emplacement during an arc magmatic flare-up at ~170-165 Ma, and similarity in terms of petrology and tectonic setting to other Phanerozoic SLIPs including the mid-Tertiary Sierra Madre Occidental of Mexico. This North American Jurassic arc SLIP flare-up is synchronous with a high volume episode of silicic magmatism in the Chon Aike SLIP of southern South America and the Antarctic Peninsula related to crustal extension across the proto-Pacific margin of Gondwana. The inception of this voluminous bi-hemispheric episode of explosive volcanism correlates tightly to Bajocian (170-168 Ma) climate change and global carbon isotope excursions suggesting a cause and effect relationship.