MINERAL CHEMISTRY AND GEOCHEMISTRY OF THE GRANITE ROCKS OF SERRA DOS LOPES STOCK, SOUTHWESTERN SÃO PAULO STATE

Geochemistry ans mineral chemistry of the granitic rocks of Serra dos Lopes Stock, southeast of São Paulo state

Abstract

The Neoproterozoic granitic rocks of the Serra dos Lopes stock are located in the southwestern region of São Paulo State, within the municipalities of Piedade and Pilar do Sul. They are associated with the magmatism of the Agudos Grandes Granitic Batholith in the Apiaí Terrain. These rocks form an intrusive body covering 99 km² within the metavolcanic-sedimentary sequence of the Votuverava Group (Açunguí Supergroup), following a general north-south orientation imposed by the Taxaquara Shear Zone. The rocks consist primarily of syenogranitic to monzogranitic varieties, exhibiting pink and white coloration, with rare occurrences of monzonite. Porphyritic types dominate, though isotropic textures are also present. Biotite is the dominant mafic mineral. Petrographic analysis identifies microcline, quartz, oligoclase, albite, and biotite (annite and siderophyllite) as the main mineralogical components. The granites are peraluminous and correlate with I-type granites of the high-potassium calc-alkaline to shoshonitic series, classified as late- to post-collisional. They are interpreted as satellite magmas, differentiated from the evolution of the Agudos Grandes syn-collisional batholith, a significant magmatic event in the construction of the Ribeira Magmatic Arc. These granites are associated with the transtensional structures of the Taxaquara Shear Zone, marking the final stage of the collisional event of the Ribeira Orogeny and representing the late geotectonic stabilization of the Apiaí Terrain.