MACIÇOS INTRUSIVOS DO SUL DO ESPÍRITO SANTO E SEU CONTEXTO REGIONAL

Resumo

A section of the Brasiliano Mobile Belt (650-450 Ma) was investigated in Espírito Santo from structural, petrological and geochemical poínts of víew. The Archean granulític rocks of the Juiz de Fora Complex show less recrystallization after formation of large scale folds than the Alegre Complexo Both complexes are separated by a steeply Edipping ductile shear zones (Guaçuí Lineament). In the Alegre, Complex anatexis and granitisation ocurred in a relatively early stage of deformation. Later gregarious basíc to intermediate zoned diapirs intruded all units. Four of these diapirs have been mapped (scale of 1:50.000) and sampled. Petrological and geochemical data indícate a mantle origin magma mixíng, differentiation and host rock aasimilation. This group of zoned plutons shows a, complex ínternal structure with large compositional varíatíon, gradíng from olivine OPX-hornblende-gabbros, through OPX-CPX-biotite diorítes, CPX-biotite monzodiorites up to biotites syenomonzonítes (Jacutinga-Torre Complex and to a smaller extent, Venda Nova Complex). OPX-hornblende-biotite monzogabbros and monzodiorites, hornblende-biotíte granodiorites and allaníte-sphene-bíotite granites occur in Santa Angélica and Castelo Complexes. A contemporaneous megmatísm of melanocratic and leucocratic rocks produced a complicated pattern of mixed rocks. The presence of mantled feldspars, the different Rb/Sr rations for different lithologies, inherited zircons together with some other petrographic and geochemical characteristics are indícative of fusion of the mantle material which was mixed with different amounts of crustal melting, thus originating hybríd plutons of post-collision types. In this paper, ít ís analysed the problem of rock contamínation, differentiation and production of granitic magma. The showed data was interpreted by a model which involves a large scale thrustíng of the Juiz de Fora Complex towards the west over the Alegre Complexo. This also suggests a continent-continent collísíon which was followed by domic upwarping that exposed the structurally deeper Alegre unit.