Basement geology of the northwestern sector of Sierra de San Luis

Abstract

Although in the past few years numerous studies about the geology of the basement of the Sierra de San Luis have been carried out, the majority of these have been focused on the southern region. In this study the cartography of the different lithologies of the northern region basementhas been produced, establishing the relationships with well known units. The metamorphic rocks are represented by the here called Las Higueras metamorphites, a sedimentary sequence with acid and intermediate volcanic intercalations, formed by pelites, gray wackes and calcosilicatic rocks, metamorphosed under the conditions of the lowest subfacies of low pressure facies amphibolites and affected by three deformation phases. In parts these rocks have suffered contact metamorphism produced by two different magmatics events. The protoliths of Las Higueras metamorphites show important analogies with the San Luis Formation, which is described in the more southern areas. The igneous rocks of the region correspond to the Quines tonalite and to thetonalites and monzogranites Potrero de Gutierrez. These bodies have been subsequently intruded at the first metamorphic event and in a prior topartially contemporary manner at the second metamorphism. Judging by their geology and petrography, they show analogies to the Famatinian Ordovician preorogenic granitoids. El Hornito and La Poblacion granites have also been recognised, belonging to the denominated Famatinian post-orogenic granitoides, accompanied by numerous dykes of acid composition and of mafic dykes anden claves.