Significado geotectónico de las suturas de Sierras Pampeanas orientales en la faja orogenica cordoba: posible correlacion con orogenos brasilianos

Abstract

We propose to correlate the Pampean orogen with the Brasiliano belts, based on work started in 1994. The Precambrian-Cambrian tectonic evolution of the Pampean Ranges of Cordoba includes the Neoproterozoic development of a passive margin on the western side of the Rio de La Plata Craton. Subsequently, this passive margin evolved into an eastward dipping subduction zone as shown by the relative position of the rocks interpreted to have formed in an accretionary prism, a magmatic arc and a retroarc basin. The latest Precambrian event was the collision between the Rio the La Plata Craton and the Pampia Terrane (Grenville age craton?) which followed the closure of the ocean basin to the west of this arc.The suture between the Rio de La Plata Craton and the Pampia Terrane is located in the western ultramafic belt of the Sierras de Cordoba, it coincides with the Sierras Grandes Ranges. This suture separates the two distinctive tectonic domains which form the basis for the above tectonic interpretation. 1) The external, western domain is characterized by a peripheral fold and thrust belt developed in a dominantly clastic sedimentary prism, and a post collisional foreland basin. Evidence for the post-collisional basin comes from small outcrops of coarse clastics in the Sierras de San Luis to the South and the Puncoviscana basin to the north. 2) The internal, eastern domain is characterized by magmatic and high grade metamorphic rocks (migmatites and granulites) associated with ductile shear zones. These features are superimposed on a carbonate-clastic prism which appears to have formed on a passive margin. The polarity of the internal and external domains, the ultramafic belts, the age and evolution of the Cordoba Orogen are consistent with a correlation of the belt with the Paraguay-Araguaia belt in Brazil.