Review of the polyorogenic Palaeozoic basement of the Argentinean North Patagonian Andes: age, correlations, tectonostratigraphic interpretation and geodynamic evolution.

The presence of metamorphic rocks along the North Patagonian Andes is well known. All these metamorphic rocks are intruded by plutonic igneous rocks of Devonian, Carboniferous and Permian ages. The geographic localization of these rocks in the same geological province led to a first approach to grouping them under the same lithostratigraphic unit (Colohuincul Complex). Later studies, based on geological mapping and geochronological, structural and petrological data, gave an account of the differences among these rocks. The main distinction is that these metamorphic rocks were affected by two dissimilar Palaeozoic tectono-metamorphic events. The oldest one is related to a lower Palaeozoic orogenic event (Famatinian orogeny) and the other one to an upper Palaeozoic event (Gondwanan orogeny). For this reason, it is necessary to distinguish and group the metamorphic rocks from the North Patagonian Andes basement in two different tectonostratigraphic units: the Colohuincul Complex (Cambrian-Ordovician) and the Cushamen Complex (middle Silurian-early Carboniferous) in order to better understand the geodynamic evolution of the Gondwana southwestern margin during the Palaeozoic. [ABSTRACT FROM AUTHOR]