GEOCHEMISTRY AND MINERAL CHEMISTRY OF THE POST-COLLISIONAL GRANITE ROCKS OF SGUARIO STOCK, APIAÍ TERRANE, SOUTHEAST OF SÃO PAULO STATE

Abstract

ABSTRACT – The post-collisional neoproterozoic rapakivi granitic rocks of the Sguario Stock are located in the southwest region of São Paulo state, in the municipality of Ribeirão Branco and are related to Três Córregos Granitic Batholith magmatism in the Apiaí Terrain. These constitute an intrusive body, of 70 km², in the Água Clara Formation metavolcanicsedimentary sequence (Açunguí Supergroup) and the Itaiacoca Group, elongated according to the NE-SW general direction imposed by the Itapirapuã Shear Zone. These rocks are represented by compact syeno- to monzogranitic varieties, of red, pink and gray color, dominating the porphyritic types and secondarily the equi- to inequigranular types, in addition to late aplitic and pegmatitic phases. Viborgite rapakivi texture are common and biotite occurs as the dominant mafic mineral. The petrographic characteristics identify potassium feldspar, quartz, oligoclase, amphibole (edenite) and biotite (annite) as the main mineralogy. Mineral chemistry analyzes determine oligoclase, amphibole (edenite) and biotite (annite) as the main mineralogy. The rapakivi granites are peraluminous and can be correlated to the high potassium to shoshonitic calcium-alkaline series, caledonian I Type, highly differentiated, post-collisional and from the final phase of the Ribeira Magmatic Arc construction or the intraplate anorogenic environment, associated with alkaline peraluminous A type granites. These are associated with transtensive shear zones structures, at the end of the Ribeira Orogeny collisional event and characterized the final geotectonic stabilization of the Apiaí Terrane.

Keywords: Sguario Granite; Apiaí Terrain; Rapakivi; Geochemistry; Mineral Chemistry.