Tectonothermal evolution associated with crustal escale extension: an hercynian example from the Tormes gneiss dome (NW Salamanca, Iberian Massif)

[Abstract] The tectonothermal Variscan evolution ofthe Tormes Gneiss Dome is controlled by a subhorizontal ductile shear zone of crustal scale and extensional characteristics, that induced a quick exhumation ofthe deep parts ofthe metamorphic complex during crustal thinning. The shearing affected a broad band of metamorphic rocks but, as the temperature decreased, became progressively concentrated in a low-grade ductile detachment that separates two distinct units, characterized by their lithology and different tectonothermal evolution. Kinematic indicators in non-coaxial fabrics show a displacement of the hangingwall to the SE, i. e., parallel to the trend of the foldbelt. The subhorizontal shearing is related to the extensional collapse ofthe variscan crust, previously thickened during the collision tectonics