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Setting new constrains on the age of crustal-scale extensional shear zone (Vivero fault): implications for the evolution of Variscan orogeny in the Iberian massif

Research paper by Marco A. Lopez-Sanchez, Alberto Marcos, Francisco J. Martínez, Alexander Iriondo, Sergio Llana-Fúnez

Indexed on: 21 Dec '14Published on: 21 Dec '14Published in: International Journal of Earth Sciences



Abstract

The Vivero fault is crustal-scale extensional shear zone parallel to the Variscan orogen in the Iberian massif belt with an associated dip-slip movement toward the hinterland. To constrain the timing of the extension accommodated by this structure, we performed zircon U–Pb LA-ICP-MS geochronology in several deformed plutons: some of them emplaced syntectonically. The different crystallization ages obtained indicate that the fault was active at least between 303 ± 2 and 287 ± 3 Ma, implying a minimum tectonic activity of 16 ± 5 Ma along the fault. The onset of the faulting is established to have occurred later than 314 ± 2 Ma. The geochronological data confirm that the Vivero fault postdates the main Variscan deformation events in the NW of the Iberian massif and that the extension direction of the Late Carboniferous–Early Permian crustal-scale extensional shear zones along the Ibero-Armorican Arc was consistently perpendicular to the general arcuate trend of the belt in SW Europe.