4th Swiss Geoscience Meeting, Bern 2006 Tertiary tectono-metamorphic evolution of the Leventina

The infrapenninic Leventina nappe represents the lowermost unit outcropping in the Alpine nappe stack and corresponds to the northernmost slice of the European margin that was entrained into the Alpine continental accretionary prism during the Alpine continental collision. The internal structural configuration and the pressure-temperature conditions of the unit during the Alpine metamorphic event are barely known and have never been the subject of research in recent times. This study of the internal structure of the Leventina nappe, through detailed mapping of structures and shear zone patterns, and the investigation of the Si (pfu) content of white micas (coexisting with biotite + K-feldspar + quartz) along a north–south profile, yield details regarding the tectonic and metamorphic history of the Leventina nappe. These new data allow the proposition of a kinematic model for this unit during the Tertiary Alpine tectonics. The Leventina nappe underwent three phases of ductile deformation. Foliation S1 is mostly subparallel to the regionally dominant structural fabric, the S2 foliation. This foliation is penetratively developed in the hanging wall toward the Simano nappe