Research Article| July 01, 2012 The geochronology of volcanic and plutonic rocks at the Questa caldera: Constraints on the origin of caldera-related silicic magmas Matthew J. Zimmerer; Matthew J. Zimmerer † New Mexico Bureau of Geology and Mineral Resources, 801 Leroy Place, Socorro, New Mexico 87801, USA †E-mail: mjz1983@nmt.edu Search for other works by this author on: GSW Google Scholar William C. McIntosh William C. McIntosh New Mexico Bureau of Geology and Mineral Resources, 801 Leroy Place, Socorro, New Mexico 87801, USA Search for other works by this author on: GSW Google Scholar GSA Bulletin (2012) 124 (7-8): 1394–1408. https://doi.org/10.1130/B30544.1 Article history received: 11 May 2011 rev-recd: 25 Feb 2012 accepted: 28 Feb 2012 first online: 08 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Matthew J. Zimmerer, William C. McIntosh; The geochronology of volcanic and plutonic rocks at the Questa caldera: Constraints on the origin of caldera-related silicic magmas. GSA Bulletin 2012;; 124 (7-8): 1394–1408. doi: https://doi.org/10.1130/B30544.1 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGSA Bulletin Search Advanced Search Abstract Volcanic and plutonic rocks exposed in the Latir volcanic field, northern New Mexico, provide an opportunity to examine the timing of caldera-related magmatic processes. Fifty-five mineral separates were dated using the 40Ar/39Ar method. Volcanism began at 28.5 Ma and ended at 22.7 Ma, climaxing with the eruption of the high-SiO2 peralkaline Amalia Tuff from the Questa caldera at 25.39 ± 0.04 Ma. Following caldera collapse, four resurgent plutons were emplaced between 25.4 and 25.0 Ma. Previous geochemical studies suggested that the peralkaline phases of two resurgent plutons and a peralkaline ring dike represent an intrusive equivalent to the Amalia Tuff. A new analysis of K-feldspar from the ring dike yielded a plateau age of 25.38 ± 0.04 Ma, supporting this previous conclusion. Only these small-volume peralkaline intrusions are temporally indistinguishable from syncaldera magmatism. The structurally lower resurgent plutons were emplaced ∼100–400 k.y. after the Amalia Tuff eruption and are therefore too young to be the nonerupted, more-mafic parts of Amalia Tuff magma chamber, implying that the Amalia Tuff magma was not generated via in situ differentiation in the upper crust. Following resurgent plutonism, five additional plutons were emplaced between 24.9 and 19.3 Ma along the southern caldera margin and south of the caldera. Thermochronology indicates that most plutons rapidly cooled following emplacement, but that some were subsequently reheated during protracted postcaldera pluton emplacement. The timing of pluton emplacement at the Questa caldera indicates that only small volumes of the intrusive rocks are the same age as the caldera eruption and that most of the intrusive rocks record postcaldera magmatic processes. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.