Subduction-related Jurassic volcanism in the Mesa Central province and contemporary Gulf of Mexico opening

摘要

Jurassic volcanic successions in the Mesa Central (central Mexico) are considered as remnants of the EarlyMiddle Jurassic Nazas volcanic province, which is interpreted either, as a volcanic arc, result of the eastward subduction of paleo-Pacific plate underneath north-central Mexico or as a volcanic belt influenced by transtension related to the breakup of Pangea and subduction from the paleo-Pacific domain. We present new geochemical and geochronological data of Jurassic volcanic rocks exposed in Durango, Coahuila, Zacatecas, San Luis Potosi and Nuevo Le ' on that confirm observations from previously reported localities in northeastern Mexico, a subduction signature for all studied rocks and ages of volcanism between 191 and 165 Ma (U-Pb, zr, LA-ICPMS). Initial epsilon Nd values (t = 180 Ma) lye by -4.56 to 0.06 for samples from Real de Catorce and Charcas, in San Luis Potosi, Villa Juarez and Sierra de Ramirez, Durango and La Ballena, Zacatecas. Such results are indicative of a depleted mantle source and partial mixing of juvenile mantle and crustal melts. Nd model ages between 695 and 1125 Ma suggest a Precambrian underlying crust. On another hand, volcanic rocks interbedded with redbeds, which are interpreted as basal deposits related to the Gulf of Mexico initial rifting, and their associated extensional sub-basins, provide with stratigraphic evidence that links early Jurassic volcanism and the opening of the Gulf of Mexico. In any case, the subduction process may have influenced NW-SE oriented extension in the Gulf of Mexico area, as an atypical back arc inland, whose extension axis made a high angle with the ancient Pacific trench. Whereas the classical model of a continental arc-back arc setting, placed close to and parallel to the trench, might be exclusive of continental margins of thick, vast and well-consolidated landmasses, variants in the geometry of such volcanic and extensional settings could be controlled by heat flow patterns in the mantle, crustal thickness and composition, as well as tectonic plates dynamics.