Deformation regimes and fabrics in lower to mid-crustal large-scale transcurrent shear zones: the Lancinha-Cubatão shear system, Ribeira belt, Brazil

Abstract

The Embu Terrain occurs in the central and southern portions of the Ribeira Belt with the Apiaí, Curitiba and Paranaguá Terranes. It is composed of an association of metasedimentary rocks of lower to upper amphibolite facies, with concordant intercalations of calcissilictic, metaultrafic, metamaphic and quartzite rocks. This terrain is one of the key pieces in the understanding of the geotectonic evolution of the Ribeira Belt, on which there are currently two antagonistic geotectonic models. One of the models places the Ribeira Belt as a collisionous orogen, while the other as an intracontinental orogen. This project aims to quantify the metamorphic processes recorded in Embu Terrane, mainly in its western portion, to complement existing data and to compare these two geotectonic evolution models. In addition, it will be studied its southeastern limit with the adjacent terranes (Apiaí, Costeiro and Curitiba Terrains), given by the Cutabatão Megafault, the largest structure in the Ribeira Belt. The geotectonic role of the Cubatão Fault is also the subject of controversial interpretations, having been interpreted as a suture zone or a late fault of lateral escape. The objectives of the project should be achieved using the following methods: fieldwork on regional and detail scale, petrography, geothermobarometry, geochemistry, microstructural analysis, crystallographic preferential orientation and geochronology by isotopic methods. (AU)