Edades U-Pb en circones detríticos de las metasedimentitas del Cordón del Peñasco, Precordillera de Mendoza

Abstract

In central-western Argentina, a belt of slope and deep marine metasedimentary rocks is associated with mafic and ultramafic bodies throughout the western margin of the Precordillera. The belt is assigned to the late Neoproterozoic-Early Devonian based on U-Pb data and fossil fauna. It is considered to represent the suture zone between the Cuyania -to the east- and the Chilenia -to the west- terranes. We present here the first U-Pb data on detrital zircons of metasedimentary rocks from the Cordón del Peñasco area, northern Precordillera of Mendoza. Two metasandstones from the same unit (Peñasco Formation) were collected at the eastern- and westernmost sectors of the study area. They yielded different zircon morphologies, population distributions and maximum depositional ages (534 Ma for the westernmost sample and 458 Ma for the easternmost one). The obtained results confirm that local stratigraphical scheme needs revision. They also confirm the existence of a basin which separated the Cuyania and the Chilenia terranes at early Cambrian times. Besides, thedifferent zircon populations registered reveal a change in provenance areas, which could be possibly related to the Ocloyic orogeny during middle-late Ordovician.