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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) |
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| Authors: | Rowe M C; Wolff J A; Gardner J N; Ramos F C; Teasdale R; Heikoop C E |
| Institution: | 1Department of Geological Sciences, University of Texas at Austin, Austin, TX 78712, USA 2Department of Geology, Washington State University, Pullman, WA 99164, USA 3Earth and Environmental Sciences, Los Alamos National Laboratory, Los Alamos, NM 87545, USA 4Department of Geological Sciences, Central Washington University, Ellensburg, WA 98926, USA 5Department of Geological and Environmental Sciences, California State University, Chico, CA 95929, USA 6310 Garver Lane, White Rock, NM 87544, USA |
| Abstract: | The Miocene–Quaternary Jemez Mountains volcanic field(JMVF) is the site of the Valles caldera and associated BandelierTuff. Caldera formation was preceded by > 10 Myr of volcanismdominated by intermediate composition rocks (57–70% SiO2)that contain components derived from the lithospheric mantleand Precambrian crust. Simple mixing between crust-dominatedsilicic melts and mantle-dominated mafic magmas, fractionalcrystallization, and assimilation accompanied by fractionalcrystallization are the principal mechanisms involved in theproduction of these intermediate lavas. A variety of isotopicallydistinct crustal sources were involved in magmatism between13 and 6 Ma, but only one type (or two very similar types) ofcrust between 6 and 2 Ma. This long history constitutes a recordof accommodation of mantle-derived magma in the crust by meltingof country rock. The post-2 Ma Bandelier Tuff and associatedrhyolites were, in contrast, generated by melting of hybridizedcrust in the form of buried, warm intrusive rocks associatedwith pre-6 Ma activity. Major shifts in the location, styleand geochemical character of magmatism in the JMVF occur withina few million years after volcanic maxima and may correspondto pooling of magma at a new location in the crust followingsolidification of earlier magma chambers that acted as trapsfor basaltic replenishment. KEY WORDS: crustal anatexis; fractional crystallization; Jemez Mountain Volcanic Field; Valles Caldera; radiogenic isotopes; trace elements |
| Keywords: | : crustal anatexis fractional crystallization Jemez Mountain Volcanic Field Valles Caldera radiogenic isotopes trace elements |
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