Heavy minerals of saprolites of pegmatites intrusive in the Resende Costa Orthogneiss: characterization and correlation with the São João del Rei Pegmatitic Province, Minas Gerais State, Brazil

The study of heavy minerals is an important tool for the correlation between pegmatites, as bodies with similar mineralogy and spatial correlation are usually interpreted as cogenetic, sharing the same source. The heavy minerals of pegmatites intrusive into Resende Costa orthogneiss were described by stereomicroscopy, Raman spectroscopy, X-ray diffraction and backscattered electron images from scanning electron microscopy. These pegmatites are mineralized in Nb-Ta and Sn, similar to the pegmatites intrusive into the Ritápolis metagranite. The pegmatites intrusive into the Cassiterita orthogneiss exhibit only minerals of the microlite group while cassiterite is not observed. An intergrowth between phases of Nb-Ta-Ti proves to be decisive to characterize the intrusive pegmatites in the Resende Costa orthogneiss and differentiate them from bodies related to both meta granitoids and orthogneiss. It is suggested the presence of at least three generations of pegmatitic bodies in the Pegmatitic Province of São João del Rei, being correlated to the protoliths of the Cassiterita orthogneiss, the Resende Costa orthogneiss and the Ritápolis meta granitoide. (author)