Origin and metamorphism of graphite from Formiga, Minas Gerais (Brazil)

During the Paleoproterozoic Era, Brazilian cratons experienced orogenic events that modified archean basement and sedimentary successions. In southern São Francisco Craton, it can be recognized evidence of an event happened between Rhyacian Orosirian periods. It is related to closure oceanic basin at this time, which led collision Archean Divinópolis Campo Belo metamorphic complexes. Graphite schist occurs close cities Formiga Itapecerica (Minas Gerais), located these To contribute understanding origin metamorphism graphite from Formiga, petrographic studies, X-ray diffraction (XRD) Raman spectroscopy analyses have been done. XRD methods revealed temperatures recorded by are around 460°C. However, data showed crystallite sizes correspond higher grade conditions (amphibolite granulite facies). Temperatures 460°C probably associated with hydrothermal processes along faults in post-collisional stage. The presence todorokite, a mineral typical deep-sea Mn nodules formed microorganisms, association suggests biogenic for occurrence.