In the area of Mt. Filau, P.ta Padenti and Mt. Praneddu, near Domus de Maria (southern Sardinia, Italy ), a granitic basement is overlaid by blastomylonitic rocks. Petrographic observations show that the blastomylonisis had its effect on original crystalline rocks, either granitic facies or gneiss. This situation offers problems of great interest for the geology of region, particularly connected with the possible existence of granites of different age or of gneissic facies: the latter not easily placed in the local petrological environment.