EVOLUÇÃO CRUSTAL DO BLOCO SÃO ROQUE, NA REGIÃO SUDESTE DO ESTADO DE SÃO PAULO

Abstract

Field mapping in the region between Itu, Cabreuva and Pirapora do Bom Jesus - SP, an area of 3.000 km2 , has added much to our understanding of late Proterozoic histories in São Paulo State, especially in the São Roque block, between the Itu - Jundiuvira and Taxaquara shear zones. Mapping of the adjacent Jundiai and Embu blocks also contributed importantly. Some of the principal conclusions include: (i) an initial extension of the Transamazonian crust around 1.8 Ga, with sedimentation and volcanism of the Serra do Itaberaba and São Roque groups; (ii) assuming an eastward dipping A-Type subduction during the Brazilian/Panafrican Cycle, mere was a collision with an initial Dn+l/+2 deformation, with sub-horizontal foliation and northwest/northeast vergence; (iii) Dn+3 deformation, was observed in the lithologies of the Itapira Complex, Serra do Itaberaba and São Roque groups and related igneous rocks. Based largely on the interpretation of the Dn+3 deformation, there was an initial transtensional regime with emplacement of Brazilian granites followed by a transcurrent/transpressional regime. This transcurrent/transpression regime produced normal folds and vertical mylonitic foliations in the shear zones, especially near the limits of the blocks. A later, brittle tectonic phase with a northeast-southwest trend also exists, in the Sorocaba Massif.