Résumé
The study area is located in the Galicia-Trás-os-Montes Zone (GTMZ zone, Arenas et al. 1986; Farias et al. 1987 Fig. 1) a part of the Iberian hercynian massif. The GTMZ belongs to the internal zone of the Hercynian belt and is composed of a relative autochthonous and parautochthonous units overthrusted by allochthonous complexes. Studied area is located in the Schistose Domain (parautochthonous Marquínez García 1984) which is composed by a monotonous sequence of schists. Rocks of this domain exhibit a well-developed regional schistosity related to nappes emplacement (D1 and D2 events) and are affected by NS-trending crenulation and folds (D3 event) characterized by a high-temperature metamorphism leading to local development of migmatites. Four generations of granites (G1 to G4), well identified in NW Spain by their textural, geochemical characteristics and crosscutting relationships are present in the studied area. G1 to G3 granites are coeval with late with D3 event. G1 granites are syn-kinematic porphyric biotite granites. G2 granites are syn-D3 two micas granites and leucogranites (Capdevila and Floor 1970; Barrera Morate et al. 1989). G3 granites are biotite-dominant two mica granites (Barrera Morate et al. 1989). G4 granites are post D3 (Capdevila and Floor 1970; Bellido Mulas et al. 1987; Barrera Morate et al. 1989). Gold mineralizations are spatially associated with G3 granites, and Bruès, the main deposit, is located on the North-western edge of the Boborás granite roof (fig. 1). Sn-W deposits are represented, by disseminated and vein-type mineralizations. Sn,Ta,Li,Nb±W disseminated mineralizations are hosted by REE-pegmatites-aplites (Fuertes-Fuente and Martín-Izard 1998), crosscut by Sn-bearing quartz veins, spatially associated with G2 granites. The main pegmatite field is the Couso district, located on the Eastern edge of the La Estrada-Cerdedo G2 granite (fig 1). Sn-W±Ta±Nb vein-type deposits are also spatially associated with G2 granites. The most important deposits are located on the Eastern edge of the composite G1-G2 Beariz granite (fig 1).