Abstract
The geological mapping (scale: l :50.000) undertaken southwest of Cajati City, south of Sao Paulo State, revealed that the several lithological associations suffered an intense deformation, responsible for a pervasive mylonitization of ali lithologies. The stretching lineations and the shear sense indicators associated to this mylonitization, such as S-C foliation planes, asymmetric porfiroclasts and boudins, suggest an extensional tectonics for this deformation, with extensional component to ESE, associated to sinistrai strike-slip motion. Sheath folds and synmylonitic folds, with axes parallel to the stretching lineation indicate that the non-coaxial deformation reached high values of shear strain. This deformation occured in amphibolite to greenschist facies conditions, and microstructures suggest the mylonitic fabric postdates the peak of the metamorphism. The transformation of kyanite to sillimanite suggest a decrease in pressure during progressive metamorphism. Under the presence of the kyanite indicate a previous compressive history. Later on, at a shallow structural levei, crenulation and asymmetric north-vergent folds associated to discrete ruptile-ductile discret thrusts, complete the structural evolution of the investigated area. The tectonic significance of this structural pattern, in Brasiliano Orogeny scenery in this crustal segment, needs of more detailed studies.
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