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Abstract

The Laramide magmatic arc in the Arizpe-Mazocahui quadrangle of northcentral Sonora, Mexico, is composed of volcanic rocks assigned to the Tarahumara Formation and several granitic plutons that intrude it. The arc was built over juxtaposed crustal basements of the Caborca and Mazatzal provinces. A basal conglomerate of the >4-km-thick Tarahumara Formation overlies deformed Proterozoic igneous rocks and Neoproterozoic to Early Cretaceous strata, thus constraining the age of a contractional tectonic event that occurred between Cenomanian and early Campanian time. The lower part of the Tarahumara Formation is composed of rhyolitic ignimbrite and ash-fall tuffs, andesite fl ows, and interbedded volcani clastic strata, and its upper part consists of rhyolitic to dacitic ignimbrites, ash-fall tuffs, and volcani clastic rocks. The Tarahumara Formation shows marked lateral facies change within the study area, and further to the north it grades into the coeval fl uvial and lacustrine Cabullona Group. The age of the Tarahumara Formation is between ca. 79 and 59 Ma; the monzonitic to granitic plutons have ages of ca. 71-50 Ma. The informally named El Babizo and Huépac granites, La Aurora and La Alamedita tonalities, and the Puerta del Sol granodiorite compose the El Jaralito batholith in the southern part of the area. Major and trace element composition of the Laramide igneous rocks shows calc-alkaline differentiation trends typical of continental magmatic arcs, and the isotope geochemistry indicates strong contribution from a mature continental crust. Initial 87 Sr/ 86 Sr values range from 0.70589 to 0.71369, and ε Nd values range from -6.2 to -13.6, except for the El Gueriguito quartz monzonite value, -0.5. The Nd, Sr, and Pb isotopic values of the studied Laramide rocks permit comparison with the previously defi ned Laramide isotopic provinces of Sonora and Arizona. The El Gueriguito pluton and Bella Esperanza granodiorite in the northeastern part of the study area along with plutons and mineralization of neighboring northern Sonora have isotopic values that correspond with those of the southeastern Arizona province formed over the Mazatzal basement (Lang and Titley, 1998; Bouse et al., 1999). Isotopic values of the other Laramide rocks throughout the study area are similar to values of provinces A and B of Sonora (Housh and McDowell, 2005) and to those of the Laramide Pb boundary zone of western Arizona, while the Rancho Vaquería and La Cubana plutons in the northernmost part of the area have the isotopic composition of the Proterozoic Mojave province of the southwestern United States. These data permit us to infer that a covered crustal boundary, between the Caborca block with a basement of the Mojave or boundary zone and the Mazatzal province, crosses through the northeastern part of the area. The boundary may be placed between outcrops of the El Gueriguito and Rancho Vaquería plutons, probably following a reactivated Cretaceous thrust fault located north of the hypothesized Mojave-Sonora megashear, proposed to cross ...

Protolith age of the Altar and Carnero complexes and latest Cretaceous–Miocene deformation in the Caborca–Altar region of northwestern Sonora, Mexico

“…(1) The latest Cretaceous zircon could have been derived from multiple sources in Sonora, including ranges near Cerros La Batellera (McDowell et al, 2001;Iriondo et al, 2005;Jacques-Ayala et al, 2009;Roldán-Quintana et al, 2009;González-León et al, 2011, 2017Ortega-Gutiérrez et al, 2014).…”

Mesozoic–Paleogene structural evolution of the southern U.S. Cordillera as revealed in the Little and Big Hatchet Mountains, southwest New Mexico, USA

“…Basement-involved shortening occurred inboard of the active Tarahumara volcanic arc in Sonora, Mexico ( Fig. 1; González-León et al, 2011), and active plutonic centers occurred adjacent to the flanks of uplifts and volcanic complexes developed within Laramide intermontane basins.…”

“…This geographic shift in arc volcanism is recorded by (1) ca. 115-92 Ma volcanic rocks and plutons of the Peninsular Ranges in Baja California and coastal Sonora (Wetmore et al, 2003); (2) post-90 Ma volcaniclastic and plutonic rocks of the Tarahumara arc in northern Sonora, Mexico (González-León et al, 2011); and (3) upper Cretaceous volcanic rocks and plutons in southwestern New Mexico (e.g., Hidalgo Formation and Sylvanite plutonic complex, discussed herein). Late Cretaceous to Paleogene magmatism in southern New Mexico is argued to be related to three magmatic arc episodes (e.g., McMillan, 2004) interpreted to have occurred from 76 to 70 Ma, 61 to 57 Ma, and 46 to 40 Ma ( Amato et al, 2017).…”

Digital geologic map and geochronologic, geochemical and geothermal database of the south-eastern part of the Sierra Madre Occidental, Mexico

“…The SMO SLIP covers the products of the so-called Laramide magmatic arc, developed between ⇠100 and 45 Ma along the western margin of Mexico during the subduction of the Farallon plate beneath North America (McDowell et al, 2001;Henry et al, 2003;González-León et al, 2011). Also called "Lower Volcanic Complex" (McDowell and Keizer, 1977), these rocks intrude or cover a basement which, in the southern half of the province, consists of volcano-sedimentary terrigenous successions of the Guerrero Terrane and limestone representing the westernmost part of the Sierra Madre Oriental carbonate successions (Ferrari et al, 2007).…”