Géologie sommaire de la région de Morais (Tras-os-Montes, Portugal)

The petrography and structure of the unit of Morais are described. Where visible, the unit rests with an abnormal contact upon hardly metamorphic Silurian sediments. Amphibole schists, serpentinite and metagabbro are found in the northern part of the unit, which is separated from the southern part by a transcurrent fault. Amphibole schists, amphibolites, metaperidotities, garnet pyroxenites, augengneisses and micaschists are found in the southern part. The basic and acid series have a tectonic contact; the basic series lies in a reversed position, the acid one shows a normal disposition of metamorphic zones. It is argued that the basic rocks might represent a basic initial volcanism in a geosynclinal environment and that the augengneisses and micaschists were coarse-grained sediments grading into a flysch. The emplacement of the unit of Morais, which is very similar to the unit of Bragança and the Basic Complex in W. Galicia, is not yet well understood.