RELATIONSHIPS BETWEEN DEFORMATION, METAMORPHISM AND MAGMATISM IN THE PALAEOPROTEROZOIC OF THE BAS-DRAA MASSIF (ANTI-ATLAS, MOROCCO)

The Bas-Draa massif corresponds to a silici-clastic banded sedimentary sequence recrystallized under low-grade conditions, in which the bedd ing is still well preserved. In the central part of the massif, the se quence is injected by early granitoids and recrystallizes under condit ions reaching the sillimanite-K-feldspar stability field. The primary surface is folded and cut by a penetrative axial-planar schistosity, s ubvertical and parallel to the planar fabric of the early granitoids. The features of the injected zone suggest a north-south shortening rel ated to a contact metamorphism resulting from the emplacement of the g ranitoids. The tectono-metamorphic evolution appears to be monocyclic and of Palaeoproterozoic age. Granite plutons post-date all the former lithologies.