Uma perspectiva integrada do magmatismo básico da faixa ribeira central: um estudo de caso em rochas da Bacia Andrelândia e do Complexo Juiz de Fora

Abstract

The basic magmatism of the Central Ribeira Belt, investigated through the rocks of the Andrelândia Basin and the Paleoproterozoic basement of the Juiz de Fora Complex, reflects key stages of tectonic evolution during the amalgamation of the São Francisco paleocontinent in the Neoproterozoic. In this context, petrographic, lithogeochemical, and isotopic analyses (Sm-Nd, Rb-Sr, Lu-Hf, and U-Pb in zircon) were carried out to assess the geochemical signatures and crystallization timing of these mafic bodies, as well as the high-grade metamorphic conditions to which they were subjected. The results reveal variations in trace elements (such as Ti, Zr, and REE) and in Sm-Nd isotopic values (εNd between +2 and –14), suggesting the involvement of heterogeneous mantle sources and possible episodes of crustal contamination during rifting and the subsequent development of a hyper-extended passive margin. The U-Pb ages (ranging between 760 and 653 Ma) obtained from both magmatic and inherited zircons, combined with TDM crustal residence models (1.9 to 1.1 Ga), indicate an interaction between juvenile magmas and reworked portions of the Paleoproterozoic basement. The integration of these isotopic data with structural and paragenetic features suggests multiple stages of metamorphism—from amphibolite to granulite facies—associated with Brasilian convergence (ca. 620–580 Ma). From a geodynamic perspective, the geochemical and isotopic variations in the mafic lithotypes provide new evidence on the formation of rift-type basins and their evolution into passive margins, as well as on the role of crustal reworking and basement exhumation during the amalgamation of Western Gondwana. These results contribute to a better understanding of the tectono-magmatic processes that shaped the Central Ribeira Belt and broaden perspectives regarding the Neoproterozoic geodynamic regime in southeastern Brazil.