EVOLUÇÃO DAS UNIDADES MAGMÁTICAS DO COMPLEXO GRANITÓIDE ITAQUI (PRÉ-CAMBRIANO SUPERIOR), ESTADO DE SÃO PAULO, BRASIL: ASPECTOS GEOLÓGICOS, PETROGRÁFICOS E GEOQUÍMICOS (ELEMENTOS MAIORES)

Abstract

Chemical data from the 10 magmatic units which build up the calc- alkaline granodiorite/monzogranitic Itaqui complex (State of Sao Paulo, SE Brazil) are discussed. The late Precambrian granitoid is intrusive in the low grade metamorphic Sao Roque Group, but extensive contacts are done by the expressive Taxaquara transcurrent fault. The chemical data combined with mineralogical and textural ones as well as with the intrusion sequence of the magmatic units allowed the definition of two main magmatic cycles each subdivided in two subcycles. The cycles are separated by a phase of intrusion of melaquartzmonzonite dikes and the younger cycle is followed by the emplacement of tourmaline-muscovite monzogranitic aplites possibly related to the older cycle. Each cycle/subcycle has its own magmatic evolution trend defined by several cationic diagrams and involving the fractionation of mafic (hornblende/biotite), plagioclase and accessory minerais by different mechanisms.