DETRITAL ZIRCON GEOCHRONOLOGY IN NORTHEASTERN MEXICO: TECTONIC IMPLICATIONS

U-Pb ages of detrital zircons obtained by LA-MC-ICP-MS from several Precambrian to Cretaceous rocks in northeastern Mexico, constitute very important arguments to support alternative paleogeographic and tectonic models, contrasting with classical models of the tectonic evolution of northern Mexico and the southern North American craton: 1. Precambrian to lower Jurassic rocks show Grenvillian (900-1300 Ma), pan-African (500-700 Ma) and Permo-Triassic (280-240 Ma) zircon age populations that are typical of the Oaxaquia block, disagreeing with a large left lateral displacement of nuclear Mexico from an original position in the southwestern North-American craton during the Jurassic, as proposed by the Mojave Sonora megashear hypothesis; 2. A Triassic continental succession exposed in the Sierra Madre Oriental in Nuevo León and Tamaulipas represent deposits in a fluvial system (“El Alamar river”) that according to their detrital zircon age populations and maximal ages of deposition are linked to the Carnian-Norian marine strata exposed in the Mesa Central in San Luis Potosí and Zacatecas (“Potosi fan”), disagreeing with the classical model of a north-northwest trending graben, filled with Triassic and Jurassic red beds; 3. The occurrence of early Jurassic zircons (195-175 Ma) in the early to middle Jurassic redbeds of the Huizachal Group and their absence in the Triassic redbeds allow a separation of both units usually mapped together in the past, with a consequent lost of detail in the paleogeographic and paleotectonic reconstruction; 4. Finally, detrital zircon age populations of cretaceous units exposed in the Mesa Central province have sources from the Sierra Madre and the Guerrero terranes. This is in agreement with a transition between both regions defined as tectonostratigraphic terranes and also in agreement with a model of origin and evolution of the Guerrero terrane in close geographic proximity to the Sierra Madre terrane.