The rocks between Mariana and Ponte Nova, Minas Gerais, hitherto regarded as part of the central Brazilian craton, were investigated using petrographical, optical, microchemical and X-ray methods. Surprisingly, two zones of granulite-facies rocks, typical of the coastal mobile belt, were found inside the cratonic area. P-T conditions for the different polymetamorphic rock sequences and a
... [Show full abstract] petrogenetic model for the transition zone are discussed.-J.M.H.