GEOLOGIA, PETROGRAFIA E LITOGEOQUÍMICA DO COMPLEXO GRANÍTICO TRÊS CÓRREGOS NA REGIÃO DE BARRA DO CHAPÉU E RIBEIRÃO BRANCO, SP

Abstract

In this work we consider that the Três Córregos Granitic complex is mainly made up of porphyroid to foliated granitoids. A post-tectonic granite suite and a body of augen gneisses, interpreted as a mega-enclave, also occur. The augen gneisses, with quartz dioritic to quartz monzomtic enclaves, have chemical compositions which differ from those of the more abundant Três Córregos granitoids and appear to characterize a high-Al calc-alkaline sequence. The Três Córregos granitoids are mostly porphyritic, hornblende and biotite-bearing, but leucocratic microporphyntic to equigranular granites also occur, as well as foliated granitoids with similar compositions to the other granitoids. Mafic enclaves, mostly potassic diorites, are common. The granitoids and mafic enclaves appear to define an expanded sequence with high-K calc-alkaline characteristics and incompatible element distribution, including the Rare Earth elements, with typical subduction zone components. The K-dioritic enclaves may correspond to magmas derived by partial melting of a supra-subduction zone enriched mantle, at least with some crustal contamination during its evolution, storage and emplacement. The intermediate-acid granitoids appear to be related to the mafic enclaves, but the precise mechanism of this relationship is still elusive. The post-tectonic granites are highly differentiated and probably correspond to intra-plate crustal melts.