Chemistry of tourmalines in some pegmatites of São José da Safira area, Minas Gerais, Brazil

Abstract : The tourmaline group minerals (schorl to elbaite) typically occur in the Li-bearing pegmatites from the São José da Safira region (the Oriental Pegmatitic Province (OPP) in Minas Gerais State, Brazil). The Fe/Mn ratios of the tourmalines are compared to those measured in columbite-tantalite and garnet and decrease northward continuously from the beryl-bearing pegmatites to the spodumene-bearing ones. The Fe/Mn ratio has been used as a qualitative index of fractionation which seems to reflect the regional zoning of the pegmatites around a hidden granite body. The Fe/Mn ratio values correlate negatively with the Na and Li contents. The REE, Nb, Co and Zn contents are controlled by the mineral assemblages.