Mesa Central of México

Abstract

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.