GRANITOGENESIS AND GEOLOGY OF THE ARAÇAÍBA TOPOGRAPHIC MAP REGION, SOUTHEAST OF THE STATE OF SÃO PAULO

Geology and tectono-metamorphic and magmatic evolution of the topographic sheet region of Araçaíba (SP)

Abstract

ABSTRACT - The rocks of the Araçaíba Topographic Map crop out in the southeastern region of São Paulo state and belong to the southern portion of the Ribeira Belt, within the northern sector of the Apiaí Terrane. Regionally, the area exposes Meso- to Neoproterozoic metavolcano-sedimentary rocks of the Açungui Supergroup, dominated by lithotypes of the Água Clara Formation. Locally, in the southeasternmost sector, exposures of the Lajeado Group occur, represented by the Apiaí Metagabbro, Gorutuba, Serra da Boa Vista, and Apiaí Marble formations.These units are associated with the Neoproterozoic syn-collisional intrusive granitogenesis of the Três Córregos Granite Complex, which includes the Barra do Chapéu, Lajeado, Bairro do Chapéu, Saival, and Capote granites, along with the Paiol da Telha facies, as well as the late- to post-collisional Apiaí and Correas stocks.The geological evolution of the area is governed by a Neoproterozoic tectono-metamorphic framework characterized by three phases of progressive deformation. The first two phases correspond to tangential tectonic regimes, related to the early stages of continental collision, marked by the emplacement and subsequent deformation of syn-collisional granitoid bodies. The final phase of deformation is defined by a transcurrent to transpressive regime, associated with the ascent of post-collisional stocks. Regional metamorphism is of the Barrovian type, with peak conditions reaching the lower amphibolite facies, accompanied by local contact and dynamic metamorphism of retrograde character. The syn-collisional granitoids exhibit a high-potassium, calc-alkaline, peraluminous geochemical signature, classified as I-type Cordilleran granites, typical of continental magmatic arc settings, and are interpreted as products of partial melting of deep lower-crustal sources.By contrast, the post-collisional stocks are correlated with the high-potassium to shoshonitic calc-alkaline series, showing affinities with I-type Caledonian granites, as well as peraluminous A-type alkaline granites. This post-collisional magmatism represents the final stage in the evolution of the Ribeira Magmatic Arc and defines the geotectonic reorganization associated with the crustal stabilization of the Apiaí Terrane.