Journal of South American Earth Sciences xxx (xxxx) xxx Contents lists available at ScienceDirect Journal of South American Earth Sciences journal homepage: www.elsevier.com/locate/jsames Geology and geochronology of the Jurassic magmatic arc in the Magdalena quadrangle, north-central Sonora, Mexico Carlos M. Gonzalez-Le´ on´ a,*, Michelle Vazquez-Salazar´ b,1, Teresita Sanchez´ Navarro c,2, Luigi A. Solari d, Jonathan A. Nourse e, Rafael Del Rio-Salas a, Rufino Lozano-Santacruz f, Ofelia P´erez Arvizu d, Juan Carlos Valenzuela Chacon´ b a Estacion´ Regional del Noroeste, Instituto de Geología, Universidad Nacional Autonoma´ de M´exico, Hermosillo, 83000, Mexico b Universidad Estatal de Sonora, Ingeniería en Geociencias, Hermosillo, 83140, Mexico c Universidad de Sonora, Departamento de Geología, Hermosillo, 83000, Mexico d Centro de Geociencias, Universidad Nacional Autonoma´ de M´exico, Campus Juriquilla, Santiago de Quer´etaro, QRO, 76001, Mexico e Department of Geological Science, California State Polytechnic University, Pomona, 3801 West Temple Ave, Pomona, CA, 91768, USA f Universidad Nacional Autonoma´ de M´exico, Instituto de Geología, Laboratorio Nacional de Geoquímica y Mineralogía, Ciudad Universitaria, Ciudad de M´exico, 04510, Mexico ARTICLE INFO ABSTRACT Keywords: This work reports on the geology and U–Pb LA-ICPMS zircon geochronology of a crustal section that is part of the Continental jurassic magmatic arc Jurassic magmatic arc in the Magdalena quadrangle of north-central Sonora, Mexico. This rock succession is – U Pb igneous Geochronology variably metamorphosed and strained as it was affected by Late Cretaceous shortening, intruded by early Tertiary Detrital zircon geochronology granitoids, and further exhumed in the lower plate of the early Miocene Magdalena metamorphic core complex. Geochemistry The older and more extensively exposed Jurassic unit is the >3.5 km thick Sierra Guacomea rhyolite that is Sonora Mexico composed of massive to poorly bedded rhyolite, bedded quartz-phyric rhyolitic ignimbrite and interbedded ash- fall tuffs and quartz-rich sandstone beds. Three rhyolite samples collected at different localities of its outcrops yielded concordia ages of 175.2 ± 0.9, 171.7 ± 0.6, and 171.4 ± 0.7 Ma. The quartz-phyric Rancho La Víbora, Los Vallecitos, and the Agua Caliente rhyolitic domes that are associated with the Sierra Guacomea rhyolite yield concordia ages of 176 ± 0.8, 174.4 ± 0.9 and 173.1 ± 0.8 Ma, respectively. The Rancho Los Pozos unit composed of interbedded rhyolitic ash-fall tuff and flows, sandstone, siltstone and subordinate limestone beds has an estimated thickness of 600 m and yielded a crystallization concordia age of 170.7 ± 0.6 Ma from a rhyolite bed. The porphyritic El Rincon´ granite that intrudes into the Sierra Guacomea rhyolite yields crystallization ages of 167.43 ± 0.42 and 164.4 ± 0.7 in samples from different localities. The La Jojoba metasandstone that consists of foliated, quartz-rich to arkosic strata of fluvial origin is at least 900 m thick; detrital zircon grains dated from three sandstone samples yielded dominantly Jurassic ages with peaks at 172, 170, and 163.7 Ma, and a combined maximum depositional age of ca. 163 Ma. The younger plutons are the porphyritic El Nopalito granite that has an interpreted crystallization age of 160.8 ± 0.6 Ma, and the leucocratic, two-mica, garnet-bearing La Cebolla granite that yielded a concordia age of 158.1 ± 1 Ma. These granitic intrusions record the waning magmatic pulses of the arc, in the study quadrangle, but their volcanic equivalents were not identified. Inherited zircon grains in the reported volcanic and plutonic units are only of Jurassic age, except by two Proterozoic zircon grains yielded by the El Nopalito granite. The El Salto granite augen gneiss is a xenolith dated at 1071.9 ± 5 Ma that indicates the presence of Grenvillian basement in the study area. Major- and trace-element geochemical data indicate that the volcanic and plutonic units are silica-rich, mostly high K calc-alkaline to shoshonitic rocks associated with a continental margin arc setting. The plutons are mostly * Corresponding author. E-mail addresses: [email protected] (C.M. Gonzalez-Le´ on),´ [email protected] (M. Vazquez-Salazar),´ [email protected] (T.S. Navarro), solari@ unam.mx (L.A. Solari), [email protected] (J.A. Nourse), [email protected] (R. Lozano-Santacruz), [email protected] (J.C. Valenzuela Chacon).´ 1 Present address: Programa de Maestría en Ciencias, Departamento de Geología, Universidad de Sonora, Hermosillo, M´exico 83000. 2 Present address: Posgrado en Ciencias de la Tierra, Estacion´ Regional del Noroeste, Instituto de Geología, Universidad Nacional Autonoma´ de Mexico,´ Hermosillo, Mexico´ 83000. https://doi.org/10.1016/j.jsames.2020.103055 Received 31 March 2020; Received in revised form 21 September 2020; Accepted 19 November 2020 Available online 28 November 2020 0895-9811/© 2020 Elsevier Ltd. All rights reserved. Please cite this article as: Carlos M. González-León, Journal of South American Earth Sciences, https://doi.org/10.1016/j.jsames.2020.103055 C.M. Gonzalez-Le´ on´ et al. Journal of South American Earth Sciences xxx (xxxx) xxx peraluminous, and in conjunction with trace element geochemistry data, they suggest crustal assimilation of magmas emplaced in a probably thickened continental crust. Chondrite-normalized REE patterns and primitive mantle-normalized trace element diagrams also suggest partial melting and fractional crystallization processes. The ages obtained indicate that the arc in the study area developed from ca. 176 to 158 Ma, encompassing a 17 m.y. interval of magmatism and associated sedimentation. Regional correlation and geochronologic published data indicate that the arc crustal section of the Magdalena quadrangle is part of the Jurassic magmatic arc that regionally lasted from ca. 190 to 158 Ma. Author contribution cratonal Mazatzal province (Whitmeyer and Karlstrom, 2007) is inferred to be delimited from the Caborca block of Mojave crustal affinity Carlos M. Gonzalez-Le´ on.´ Conceptualization, Investigation, Writing (Farmer et al., 2005; Nourse et al., 2005) by a NW-SE structure whose – original draft, Visualization, Funding acquisition. Michelle Vazquez-´ tectonic nature and age has not been well resolved (Fig. 1). This struc­ Salazar. Investigation, Visualization, Writing, Review, Editing. Teresita ture that was first recognized as the Late Jurassic Mojave-Sonora meg­ Sanchez´ Navarro. Investigation, Visualization, Writing, Writing – review ashear by Silver and Anderson (1974) and Anderson and Silver (2005), it & editing, Luigi A. Solari. Conceptualization, Methodology, Writing, was later interpreted to be Proterozoic (Whitmeyer and Karlstrom, Writing – review & editing, Funding acquisition. Jonathan A. Nourse. 2007), or Pennsylvanian-Permian age (Dickinson and Lawton, 2001; Conceptualization, Investigation, Writing, Writing – review & editing, Lawton et al., 2017). An alternative explanation is that this structure Funding acquisition. Rafael Del Rio-Salas. Investigation, Writing, corresponds to the Proterozoic suture zones between the Yavapai and Writing – review & editing. Rufino Lozano-Santacruz. Writing, Meth­ Mazatzal provinces, a hypothesis that requires two megashear structures odology, Writing – review & editing. Ofelia P´erez Arvizu. Writing, (Arvizu and Iriondo, 2015). Methodology, Writing – review & editing. Juan Carlos Valenzuela Rock outcrops corresponding to the basement of the Mazatzal Chacon.´ Investigation, Writing – review & editing. province in Sonora are only known in the northeastern and north­ western parts of the state. In the northeastern part, they consist of the 1. Introduction Pinal Schist that has been dated at ca. 1.6 Ga and by intruding granites of ca. 1.4 and 1.1 Ga (Anderson et al., 2005; Solari et al., 2018). In the The region of northern Sonora that belongs to the Proterozoic region of northwestern Sonora, around Sonoita and El Pinacate, Fig. 1. Location of the study quadrangle (red rect­ angle) within the southeast extent of the Jurassic magmatic arc of southwestern North America (indi­ cated by gray pattern, taken from Tosdal et al., 1989 and Haxel et al., 2005), and northwest extent of the Nazas arc (Lawton and Molina-Garza, 2014). Also shown are approximate location of reported Jurassic rocks (black outcrops), boundaries of Paleoproter­ ozoic crustal provinces (dashed lines, inferred from Pb isotopes by Wooden and DeWitt, 1991), approxi­ mate trace of the disputed Mojave-Sonora megashear (MSM), the Magdalena detachment fault (Mdf, taken from Nourse et al., 1994) and location of cities and towns mentioned in the text. (For interpretation of the references to color in this figure legend, the reader is referred to the Web version of this article.) 2 C.M. Gonzalez-Le´ on´ et al. Journal of South American Earth Sciences xxx (xxxx) xxx juxtaposition of basement rocks of the Mazatzal and Caborca blocks is (Haxel et al., 2005) that includes an ~8 km thick interlayered succession documented (Iriondo et al., 2004; Nourse et al., 2005). The Mazatzal of mostly alluvial, fluvial, eolian, calc-alkaline rhyolitic, dacitic and basement of northeastern Sonora is overlain by an incomplete Cambrian subvolcanic rocks which accumulated in continental basins from ~170 to Permian sedimentary succession of marine origin (Gonzalez-Le´ on,´ to 165 Ma. Similarly, in southeastern California and southwestern Ari­ 1986), which in turn is overlain by volcanic and sedimentary