Abstract Volcanic, sedimentary, and granitic plutonic rocks that are part of the early Mesozoic Cordilleran continental magmatic arc are exposed in a belt from the southwestern United States to Guatemala. In the Mexican states of Chihuahua, Coahuila, Durango, Zacatecas, and San Luis Potosí, these rocks form a discontinuous southeast-trending belt across north-central Mexico. Whole-rock geochemical analyses of volcanic and intrusive rocks in north-central Mexico indicate a calc-alkaline suite formed in this continental volcanic arc along the convergent margin of western North America. Paleomagnetism, field relations, and isotopic ages (40 Ar/ 39 Ar, K-Ar, Rb-Sr, and U-Pb) of 73 volcanic and intrusive rocks document the Late Triassic–Middle Jurassic age of the arc. In the region, isotopic ages commonly are reset, apparently because of thermotectonic events during the “Laramide” orogeny that led to the development of the Sierra Madre Oriental fold and thrust belt and to deep burial of the arc rocks. Available evidence suggests that the arc underwent two main phases of subsidence. One phase of extensional subsidence created intra-arc basins and a peak of volcanism throughout the arc in the Early–Middle Jurassic. A second phase began in the Oxfordian, with subsidence and initial deposition of the Zuloaga and La Gloria Formations. Continued sedimentation during this phase led to accumulation of 5–7 km of strata above the arc, as Cretaceous seas transgressed westward over inland Mexico. The similarities in age, depositional environment, clastic composition, magma types, and geochemical affinity and, more importantly, the tectonic settings that gave rise to the Nazas Formation in Mexico and La Quinta and Girón Formations in Venezuela and Colombia suggest that these two volcanic-sedimentary sequences, now hundred of kilometers apart, were once part of the Late Triassic–Jurassic continental magmatic arc. This arc extended from Alaska to South America and evolved during simultaneous subduction along the western margin of Pangea, rifting in the Caribbean–Gulf of Mexico region, and associated large-scale transpressive activity.

Abstract Middle to Late Triassic turbidite sequences are exposed in the states of Zacatecas and San Luís Potosí in central Mexico. These strata, assigned mostly to the Zacatecas Formation, accumulated in continental slope, toe-of-slope, and basin-plain environments along the passive continental margin of western Pangea. Strata of the Zacatecas Formation are age equivalent to rocks of the Antimonio Formation and Barranca Group in Sonora, the La Boca Formation in Tamaulipas and Nuevo León, and unnamed strata in Baja California. Based on their age, the Zacatecas turbidites correlate with a drop in sea level during the Permian-Triassic assembly of Pangea. The Triassic paleogeographic setting of Mexico is complex and poorly understood, because only dispersed Triassic outcrops exist across Mexico. However, the biogeographic affinities of the faunas from the Zacatecas Formation in central Mexico with those from equivalent strata in Baja California and Sonora suggest that these three regions were connected through the eastern Pacific, and that the Atlantic Ocean did not exist during the Ladinian-Carnian. The Zacatecas sequences underwent three periods of compressive deformation: one during their obduction onto the continental margin at some time during the latest Triassic-earliest Jurassic (?); a second during the Middle to Late Jurassic (Oxfordian) (?), apparently related to transpression; and a third during the Late Cretaceous to Tertiary Laramide orogeny.

Abstract Mesa Central is an elevated plateau that can be divided into two regions. In the southern region, the topography is higher than 2000 masl, except for the Aguascalientes valley. This region is mostly covered by Cenozoic volcanic rocks. The northern region shows an advanced degree of erosion, and is below 2000 masl. The crust in Mesa Central is ∼32 km thick, and it is bordered by the Sierra Madre Oriental, which has an average crustal thickness of ∼37 km, and the Sierra Madre Occidental, which has an average crustal thickness of ∼40 km. The presence of magmas below the crust is inferred, suggesting an underplating process. The oldest rocks are Triassic marine facies underlain by Jurassic continental rocks. Marine environment prevailed between the Oxfordian and the Cretaceous, forming three distinctive lithological sequences, from E to W: the Valles–San Luis Potosí Platform, the Mesozoic Basin of Central México, and marine volcanosedimentary Mesozoic rocks. All of the above rocks have plicative deformation and inverse faulting, which was produced during the Laramide orogeny. An angular unconformity separates these lithological sequences from the continental Cenozoic rocks. The bottom of the Cenozoic sequence consists of conglomerate with andesitic and rhyolitic volcanic rocks. These were followed by Oligocene topaz-bearing rhyolites, and the uppermost part of the Cenozoic sequence is Miocene-Quaternary alkaline basalt. The boundaries of Mesa Central are the Sector Transversal de Parras and major fault systems active during the Cenozoic to the E, W, and S. A major structure, the San Luis–Tepehuanes fault system, separates the northern and southern regions of Mesa Central. The majority of the mineral deposits found in Mesa Central or in its vicinities, especially epithermal deposits, is located on the traces of the major fault systems described above. The data available suggests that the structures associated with the major fault systems controlled the emplacement of both volcanic-hypabyssal rocks and mineral deposits.