Joints orientation related with the magmatic anisotropy in the Trives granitic massif (NW Spain).

The study of brittle fractures in the Trives granite massif (northern part of the Iberian Variscan belt) reveals the existence of three subvertical se ts of joints (NW-SE, NE-SW and NNE-SSW-striking) and a subhorizontal set. T he orientation distribution of joints may be interpreted as a function of t he orientation, and degree of anisotropy, of the continuous deformation tha t the granite underwent around the solidus by the end of its emplacement, a nd of the location within the massif in relation to the surrounding country rocks. The subvertical NW-SE, NE-SW and subhorizontal sets of joints displ ay geometric relationships with foliation and lineation and can be attribut ed to primary joints. The NNE-SSW set of joints corresponds to the Late-Var iscan fracturing that is evidenced geologically in the country rocks. (C) 2 000 Academie des sciences / Editions scientifiques ct medicales Elsevier SA S.