Interplay of Miocene rift tectonics and rhyolitic magmatism in the southern Jemez Mountains, New Mexico
Gary A. Smith and Scott D. Lynch
A reconstruction of the late Miocene structural and volcanic history in the Jemez Mountains, New Mexico, documents the interplay of Rio Grande rift faulting, the eruption of rhyolitic magma, and the basinal preservation of eruptive products. Crustal melting generated a batholith that was incrementally tapped along NNW-striking and NE-striking faults that parallel regional rift faults and reactivated basement structures, respectively. Bearhead Rhyolite (6.5 – 7.1 Ma) was extruded during more than 40 eruptions from more than 20 fault-controlled vents during approximately 0.5 m.y. Simultaneously with this volcanic episode, enhanced rift-basin subsidence (~ 1 km/my) along the NNW- and NE-striking faults above the postulated batholith formed the Bearhead basin, where the best-preserved record of Bearhead Rhyolite pyroclastic deposits and related volcaniclastic sediment basin-fill strata accumulated. Coeval volcanism, faulting, basin subsidence, sedimentation, and hydrothermal alteration document the interplay of extensional deformation, magma generation, and the location of vents and style of volcanism.
- Smith, Gary A.; Lynch, Scott D., 2007, Interplay of Miocene rift tectonics and rhyolitic magmatism in the southern Jemez Mountains, New Mexico, in: Geology of the Jemez Region II, Kues, Barry S.; Kelley, Shari A.; Lueth, Virgil W., New Mexico Geological Society, Guidebook, 58th Field Conference, pp. 262-267.