Stretching lineations in high-pressure belts: the fingerprint of subduction and subsequent events (Malpica-Tui complex, NW Iberia)

The evolution of tectonic flow has been studied in an exposed continental subduction system of the Variscan belt, the Malpica-Tui Complex of NW Iberia, where structural data are used to establish the kinematics and flow geometry during the whole deformation history. Structural analysis reveals reorientation of successive lineations by subsequent deformation events, and especially by late strike-slip tectonics. Analysis of the deflection patterns in the lineation map permits us to establish the original trend of lineations. The data expose the role of thrust and nappe tectonics and non-coaxial deformation in the hinterland of a collisional belt showing a dominant orogen-parallel lineation pattern. Following oblique subduction, contractional ductile thrusts transported and emplaced a part of the subduction system onto the adjacent mainland following vectors normal to the orogenic trend. However, the finite stretching lineation in associated recumbent folds is oblique to the orogenic trend and suggests overprinting by dextral shearing, probably owing to lateral components of the Gondwana and Laurussia convergence. Subsequently, extensional structures dismembered the tectonic pile, moving the pieces obliquely with respect to the trend of the collisional belt. Orogen-parallel strike-slip shear zones later produced major reorientation of the pre-existing tectonic fabrics towards their shear planes.