The region of São José do Rio Pardo is made up of gneisses, granulites and migmatites of Precambrian age. Two granulitic varieties are described: acid alaskit granulites and pyroxene granulites both of which together with normal gneisses form the paleosoma of migmatites. The pyroxene granulite belongs to a true charnockitic series with the chemical caracteristic of differentiated calc-alkaline rocks. Geochronological determinations indicate an age of about 600 m.y. for the migmatite formation, and somewhat older ages for granulites. Metamorphic differentiation, chiefly through anatexis, producing anhidrous (charnockitic} residual associations, seems to have been the principal factor responsible for the formation of the granulites.The region of São José do Rio Pardo is made up of gneisses, granulites and migmatites of Precambrian age. Two granulitic varieties are described: acid alaskit granulites and pyroxene granulites both of which together with normal gneisses form the paleosoma of migmatites. The pyroxene granulite belongs to a true charnockitic series with the chemical caracteristic of differentiated calc-alkaline rocks. Geochronological determinations indicate an age of about 600 m.y. for the migmatite formation, and somewhat older ages for granulites. Metamorphic differentiation, chiefly through anatexis, producing anhidrous (charnockitic} residual associations, seems to have been the principal factor responsible for the formation of the granulites.