THE TECTONO-MAGMATIC EVOLUTION OF THE OCCIDENTAL TERRANE AND THE PARAÍBA DO SUL KLIPPE WITHIN THE NEOPROTEROZOIC RIBEIRA OROGENIC BELT, SOUTHEASTERN BRAZIL

Abstract

The Occidental Terrane is envisaged as the eastern/southeastern reworked margin of the São Francisco/Rio de La Plata plate associated with an E-trending subduction under the Congo plate. The Paraíba do Sul Klippe is part of the Oriental Terrane, envisaged as a portion of the Congo plate. A collisional-stage resulted in intense westward deformation of the Occidental Terrane under intermediate pressure metamorphism (syn-D1+D2 events). A late-collisional stage resulted in subvertical folding and steep shear zones (D3 event). Both stages were associated with voluminous crustal-derived granites. U-Pb and Sm-Nd geochronology as well as geochemical and structural data point to three magmatic episodes: 1) a syn-collisional stage 1; 2) a syn-collisional stage 2; and 3) a late-collisional stage. This paper presents a magmatic evolutionary model for this crustal segment of the Ribeira orogenic belt based on new geological data of Brasiliano granites and data available in the literature.