LITOGEOCHEMISTRY OF THE GRANITIC ROCKS OF THE SÃO MIGUEL ARCANJO STOCK, SOUTHEAST OF THE STATE OF SÃO PAULO

Abstract

The post-collisional Neoproterozoic granitic rocks of the São Miguel Arcanjo Stock are located in the southeastern region of the state of São Paulo, in the municipality of the same name, and are related to the magmatism of the Agudos Grandes granitic batholith, linked to the Cotia Block, of the Apiaí Terrain. It constitutes a 36 km2 body, intrusive in the rocks of the metavolcano-sedimentary sequence of the Votuverava Group of the Açunguí Supergroup, south of the Taxaquara Shear Zone, with a general NE-SW deformation direction. The rocks are represented by predominantly isotropic varieties, with monzogranitic to locally monzonitic and granodioritic composition, red to pink in color, predominantly porphyritic and, secondarily, equi-to inequigranular, medium to coarse-grained, in addition to rocks of the late aplitic and pegmatitic phases. In the central part, the igneous body is partially covered by unconsolidated Cenozoic sediments and sparse occurrences of shale from the Itararé Formation. The main mineralogy of the rocks in the stock includes microcline, quartz, oligoclase, amphibole (edenite and ferroedenite) and biotite (phlogopite and siderophyllite). The granitic rocks are peraluminous and highly differentiated, correlated with the high-potassium calc-alkaline to shoshonitic series of Caledonian Type I, of a syn-to late-collisional environment, belonging to the final phase of the construction of the Ribeira Magmatic Arc. They are associated to the transtensive structures of the Taxaquara Shear Zones, resulting from the end of the Ribeira Orogeny collisional event and characterized the final geotectonic arrangement of stabilization of the Apiaí Terrain.