Development of a Continental Volcanic Field: Petrogenesis of Pre-caldera Intermediate and Silicic Rocks and Origin of the Bandelier Magmas, Jemez Mountains (New Mexico, USA)
Department or Administrative Unit
The Miocene–Quaternary Jemez Mountains volcanic field (JMVF) is the site of the Valles caldera and associated Bandelier Tuff. Caldera formation was preceded by > 10 Myr of volcanism dominated by intermediate composition rocks (57–70% SiO2) that contain components derived from the lithospheric mantle and Precambrian crust. Simple mixing between crust-dominated silicic melts and mantle-dominated mafic magmas, fractional crystallization, and assimilation accompanied by fractional crystallization are the principal mechanisms involved in the production of these intermediate lavas. A variety of isotopically distinct crustal sources were involved in magmatism between 13 and 6 Ma, but only one type (or two very similar types) of crust between 6 and 2 Ma. This long history constitutes a record of accommodation of mantle-derived magma in the crust by melting of country rock. The post-2 Ma Bandelier Tuff and associated rhyolites were, in contrast, generated by melting of hybridized crust in the form of buried, warm intrusive rocks associated with pre-6 Ma activity. Major shifts in the location, style and geochemical character of magmatism in the JMVF occur within a few million years after volcanic maxima and may correspond to pooling of magma at a new location in the crust following solidification of earlier magma chambers that acted as traps for basaltic replenishment.
Rowe, M. C., Wolff, J. A., Gardner, J. N., Ramos, F. C., Teasdale, R., & Heikoop, C. E. (2007). Development of a Continental Volcanic Field: Petrogenesis of Pre-caldera Intermediate and Silicic Rocks and Origin of the Bandelier Magmas, Jemez Mountains (New Mexico, USA). Journal of Petrology, 48(11), 2063–2091. https://doi.org/10.1093/petrology/egm050
Journal of Petrology
© The Author 2007.