EVOLUÇÃO GEOLÓGICA DO PRECAMBRIANO NA REGIÃO SUDESTE DO ESTADO DE SÃO PAULO

YOCITERU HASUI, GEORG ROBERT SADOWSKI

Resumo


The Precambrian zone between the edge of the Paraná Basin and the coastal line, through São Paulo, is characterized by the faulted-blocks tectonic style. The blocks were grouped in four assemblages named Jundiaí, São Roque, Paranapiacaba and Costeiro. The São Roque Assemblage is constituted by the São Roque Group, an ectinitic stratigraphic unity, which is intruded by late-tectonic granitoid bodies. The geological evolution is summarized by a succession of tectonic and cristallization events: 1) pretectonic basic magmatism, 2) regional metamorphism and late-tectonic granitoid magmatism, sinchronous to the principal folding, 3) crenulation and transposition, 4) retrometamorphism. The Paranapiacaba Assemblage is formed by the Açungui Group, which includes the Pilar Ectinitic Complexe and the Embu Migmatitic Complex, both with granitoid intrusions. The recognized events of tectonism and cristallyzation are: 1) pretectonic basic magmatism, 2) regional metamorphism sinchronous to a recumbent folding not yet very well defined, 3) a second folding and a syntectonic granitoid magmatism, 4) crenulation and transposition, 5) postectonic granitic magmatism and retrometamorphism. The Costeiro Assemblage, as well as the four nuclei exposed in the Southeastern part of the Paranapiacaba Assemblage, is formed by migmatitic rocks of the Piaçaguera Complex, which we consider as part of the basement of the Brazilian Folded Belt. It suffered migmatizations, partially during the Brazilian Cycle and also postectonic granitic intrusions during that Cycle. The Jundiaí Block is constituted of pre-Brazilian migmatites (Jundiaí Complex), intruded by Brazilian postectonic granitic bodies. The transcurrent fault system began its evolution after the regional metamorphism and was active untill the end of the Brazilian Cycle. It produced the block compartimentation, which suffered some changes after the Silurian under others tectonic regimes. The geological evolution of the São Roque and Paranapiacaba Assemblages (except for the supposed pre-Brasilian nuclei) was poliphasic and related to the Brazilian Cycle. For the rest, it seems to have been poliphasic and policyclic.


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