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- Title
Estudio geológico de la falla de Vivero y estructuras asociadas en la región de Guntín (Lugo, NO de la Península Ibérica).
- Authors
A. LÓPEZ-SÁNCHEZ, M.
- Abstract
The Viveiro fault involves a complex zone more than 2 km thick of shear deformation in the region of Guntín (Lugo). The kinematical criteria related to the different structures show unequivocally a top-to-the-west motion. The deformation shows differents styles in the footwall and the hangingwall, which are separated by a brittle fault (the Vivero fault s. str.). In the former (Lugo dome), the rocks show a mylonitic foliation mainly developed after a peak metamorphic conditions into the greenschist metamorphic facies that arranges parallel to the Vivero fault. In the hangingwall, different types of structures (tectonic foliations with low dips, folds, C' type shear band cleavages, boudins, etc.) allow to establish two deformation phases. Apervasive tectonic banding characterized by quartz ductile behaviour (intracrystalline plasticity mechanism) and pressure solution was developed during the first. The second phase is characterized by the development of brittle faults which cut the previous structures and shows an associated axial planar non-pervasive crenulation cleavage of west-facing folds in which formation doesn't involve intracristalline plasticity mechanisms. From the metamorphic point of view, there are rocks in the hangingwall with andalusite porphyroblasts pseudomorphosed by mica and kyanite aggregates arranged in elongated strips parallel to the shear zone between rocks with simple regional metamorphism. These rocks are not related to granite emplacements into the hangingwall, but to heating events related to the transferred heat from the footwall and the granite emplacements in this one during the extension and unroofing of Lugo dome. The appearance of kyanite seems to indicate the existence of isolated heat sources (granitoid intrusions) and/or something rocks of the hangingwall moved away from the Lugo dome during the shear zone movement. Finally, the overprint relation of brittle structures over the ductile fabrics in the footwall is related to other Lugo dome available data, such as its metamorphic evolution, the 40Ar/39Ar cooling ages and the U/Pb crystallization age of the Tojiza pluton, to infer a relation between the Vivero fault and its related shear zone and the uplift and unroofing of the Lugo dome.
- Subjects
LUGO (Spain); SPAIN; GEOLOGICAL research; GEOLOGIC faults; FACIES
- Publication
Trabajos de Geologia, 2007, Vol 27, p97
- ISSN
0474-9588
- Publication type
Article