Evolution of the Guerrero composite terrane along the Mexican margin, from extensional fringing arc to contractional continental arc Elena Centeno-García1,†, Cathy Busby2, Michael Busby2, and George Gehrels3 1Instituto de Geología, Universidad Nacional Autónoma de México, Avenida Universidad 3000, Ciudad Universitaria, México D.F. 04510, México 2Department of Geological Sciences, University of California, Santa Barbara, California 93106-9630, USA 3Department of Geosciences, University of Arizona, Tucson, Arizona 85721, USA ABSTRACT semblage shows a Callovian–Tithonian (ca. accreted to the edge of the continent during 163–145 Ma) peak in magmatism; extensional contractional or oblique contractional phases The western margin of Mexico is ideally unroofing began in this time frame and con- of subduction. This process can contribute sub- suited for testing two opposing models for tinued into through the next. (3) The Early stantially to the growth of a continent (Collins, the growth of continents along convergent Cretaceous extensional arc assemblage has 2002; Busby, 2004; Centeno-García et al., 2008; margins: accretion of exotic island arcs by two magmatic peaks: one in the Barremian– Collins, 2009). In some cases, renewed upper- the consumption of entire ocean basins ver- Aptian (ca. 129–123 Ma), and the other in the plate extension or oblique extension rifts or sus accretion of fringing terranes produced Albian (ca. 109 Ma). In some localities, rapid slivers these terranes off the continental margin by protracted extensional processes in the subsidence produced thick, mainly shallow- once more, in a kind of “accordion” tectonics upper plate of a single subduction zone. We marine volcano-sedimentary sections, while along the continental margin, referred to by present geologic and detrital zircon evidence at other localities, extensional unroofing of Collins (2002) as tectonic switching. This “ac- that the Zihuatanejo terrane of the Guerrero all older assemblages resulted in recycling cordion” tectonics may be modified by along- composite terrane originated from the latter of zircon from all older units (1, 2, 3). (4) For strike translations. mechanism. The evolution of the Zihuatanejo the Santonian–Maastrichtian compressional The Cordillera of western North America terrane can be explained by extensional and arc assemblage, our new detrital zircon dates records most of the global crustal growth dur- compressional processes operating entirely show for the first time that arc volcanic rocks ing Phanerozoic time, and therefore it serves as within the upper plate of a long-lived subduc- of this age are present in the coastal Zihua- a modern/young analog for genesis of the con- tion zone that dipped east under the Mexi- tanejo terrane. The contractional arc de- tinents in Paleoproterozoic time. The Guerrero can margin. This process controlled crustal veloped atop assemblages 1–3, which were composite terrane of western Mexico and the growth by continental margin rifting and shortened between Turonian and Santonian Alisitos arc terrane of the Baja California Penin- addition of new igneous and volcaniclastic time (ca. 93 and 84 Ma). Taken together, the sula represent major components of this margin material during extension, followed by ac- western Zihuatanejo terrane records a more (Fig. 1). These terranes are significant because cretion and thickening of the crust during protracted history of arc magmatism than they constitute about a third of Mexico (Fig. 1), contraction. has yet been dated in other terranes of west- a portion of the continent that was tectonically Prior to this study, all Mesozoic rocks in ern Mexico, but it closely matches the history assembled in relatively recent geologic time the western part of the Guerrero composite of Baja California to the northwest. (largely late Paleozoic to Mesozoic). terrane were considered to be part of a single Most models that have been proposed for the arc. However, we divide it into four distinc- INTRODUCTION origin of the Guerrero composite terrane and tive tectonostratigraphic assemblages: (1) a the Alisitos terrane fall into two categories: an Triassic–Early Jurassic accretionary complex The western margin of Mexico is ideally exotic arc model, and a fringing arc model. In (Arteaga complex); (2) a Jurassic to earliest suited for testing two opposing models for the the exotic arc model, oceanic/island arc terranes Cretaceous extensional volcanic arc assem- growth of continents along convergent mar- were accreted to nuclear Mexico via a subduc- blage; (3) an Early Cretaceous extensional arc gins. In the first model, the continent grows tion system that dipped westward, thereby assemblage; and (4) a Santonian–Maastrich- through accretion of exotic island arcs by the closing an entire ocean basin located between tian compressional arc assemblage. (1) The consumption of entire ocean basins at multiple the arc and the continent (Tardy et al., 1994; Arteaga subduction complex forms the base- subduction zones with varying polarities. In the Lapierre, et al., 1992; Dickinson and Lawton, ment to the Zihuatanejo terrane and includes second model, protracted extensional processes 2001; Wetmore et al., 2002, 2003; Umhoefer, Grenville, Pan-African, and Permian detrital in the upper plate of a subduction zone produce 2003). The hypothetical ocean basin was re- zircon suites that match the Potosi fan of the numerous arc-related basins, some rifted off the ferred to by Tardy et al. (1994) as the “Arperos Mexican mainland. (2) The Jurassic to earli- continental margin and others formed of new basin” and by Dickinson and Lawton (2001) as est Cretaceous extensional volcanic arc as- oceanic lithosphere; these continent-fringing the “Mezcalera basin.” In this model, material basins become filled with detritus derived from derived from the Mexican continental margin †E-mail: [email protected] arcs or the continental margin, and later become would not be found within the arc, because it is GSA Bulletin; Month/Month 2011; v. 1xx; no. X/X; p. 1–22; doi: 10.1130/B30057.1; 12 figures; 2 tables; Data Repository item 2011132. For permission to copy, contact [email protected] 1 © 2011 Geological Society of America Centeno-García et al. 115°W 110°W Alisitos arc and backar 105°W Caborca terrane North 30°N 100°W America MÉ US X A Cortes ICO c terrane Oaxaquia N Cenozoic cover Oaxaquia Cortes terrane co Parral ve terrane Parral terrane re d Central terrane 25°N terrane Central Mixteca terrane terrane limi O t axaquia GULF OF 90°W MÉXICO Zacatecas Guerrero composite terrane Tahue terrane 95°W Puerto Arcelia terrane Vallarta Cuale Zihuatanejo 20°N Cenozoic volcanic cover Teloloapan Huetamo Manzanillo Guanajuato Figure 2 Mixteca Tecpan de O PA C I F I C OGalean C E Aa MÉXIC TEMALA A N GU 15°N Figure 1. Terranes of Mexico discussed in the text. This paper focuses on the Guerrero composite terrane. A geologic map of part of the Zihuatanejo terrane is shown in Figure 2. The positions of all stratigraphic columns are plotted on these maps except for column A of Figure 3, the position of which is plotted here (Cuale). postulated to have formed on the other side of ica, but also for understanding the formation of of a single arc (Lapierre, et al., 1992; Centeno- a large ocean basin. In contrast, in the fringing continents. García et al., 1993, 2003; Tardy et al., 1994; arc model, the Guerrero and Alisitos terranes This paper presents new detrital zircon and Talavera-Mendoza et al., 1995). In this paper, we represent one or several oceanic/island arcs lithostratigraphic data to show that the Zihua- divide these Cretaceous rocks into two distinct that evolved near the Mexican continental mar- tanejo terrane of the Guerrero composite terrane tectonostratigraphic assemblages by integrat- gin (Campa and Ramírez, 1979; Böhnel et al., of westernmost Mexico (Fig. 1) has a Gond- ing detrital zircon data with new stratigraphic, 1989; Centeno-García et al., 1993, 2008; Busby wana signature that indicates an origin on or structural, and petrographic data. These tec- et al., 1998, 2006; Busby, 2004; Keppie, 2004; marginal to the Mexican continental margin. In tonostratigraphic assemblages are referred to as Talavera-Mendoza et al., 2007; Mortensen other words, our new data show that the terrane “assemblage 1” (an Early to mid-Cretaceous arc et al., 2008; Martini et al., 2009). A third pos- is not exotic. Additionally, we present new U-Pb assemblage), and “assemblage 2” (a Santonian– sibility, and much less frequently proposed zircon ages that show for the first time that Cre- Maastrichtian arc assemblage). We present new model, that these terranes represent autoch- taceous strata of the study area were deposited geologic maps of these tectonostratigraphic as- thonous continental arc rocks (De Cserna et al., upon the remains of an extensionally unroofed semblages, which formed sequentially, so we 1978a; Lang et al., 1996), is inconsistent with Jurassic arc, as well as upon an accretionary discuss them by map area, from east to west. At their geochemistry and overwhelmingly marine complex basement (Arteaga complex) that was the end of the paper, we propose a model for stratigraphy. The controversy over the exotic previously described by Centeno-García (2005) further testing the hypothesis that assemblage versus fringing arc origin of the Alisitos and and Centeno-García et al. (2008). 1 records an extensional fringing oceanic arc Guerrero terranes is important, not only for tec- Prior to this study, all Cretaceous rocks in setting, and assemblage 2 represents a contrac- tonic reconstructions of western North Amer- the Zihuatanejo terrane were considered part tional autochthonous continental arc setting. 2 Geological Society of America Bulletin, Month/Month 2010 Evolution of the Guerrero composite terrane along the Mexican margin GUERRERO COMPOSITE TERRANE 2008). In addition, the Arcelia and Guanajuato tween Puerto Vallarta and Tecpan de Galeana, (WESTERN MEXICO) terranes are distinctive by virtue of being formed an inland belt at Huetamo, and a belt in central of deep-marine sedimentary rocks and basaltic Mexico at Zacatecas (Fig.