Analisi della zona di faglia di Merano-Mules presso Passo Pennes

The Merano-Mules fault is located in the Eastern Alps and belongs to the Giducarie Fault System, which represents an abrupt change in the otherwise meridian direction of the Periadriatic Line (from E-W to NE-SW). The NE-SW trending Merano-Mules fault divides the Austroalpine domain (Punta Cervina Unit) from the Oligocene intrusions of the Tonalitic Lamellae and the Southalpine Units (Bressanone Granite). The aim of this thesis is to characterize in deep detail the Merano-Mules fault zone through meso- and micro-structural analysis. A detailed geological map was realized to map the fault and related deformation zones through the Damage Index parameter. This map allowed me to define the extent of the damaged zones, which are small in the Bressanone Granite and wider in the Austroalpine paragneisses and in the Tonalitic Lamellae. In particular, in the two latter cases the damage zones are characterized by ultracataclastic levels following pre-existing phyllosilicates-rich layers in the Punta Cervina Unit, and by secondary chloritic veins likely generated by hydrothermal fluids associated with the Oligocene intrusions. The brittle deformation is probably controlled and partitioned by the inherited anisotropic fabric made up by the phyllosilicate-rich foliation of the paragneisses, and by the chlorite veins network. The deformation began with kinking and frictional sliding processes along the lepidoblastic levels and propagates to granoblastic levels evolving into cataclastic flow. This is demonstrated also by the fact that cataclastic levels have the same attitude of the foliation and often display evidence of reworking of the phyllonite horizons. Using the stress-inversion software “Win tensor 3.0.0” I have derived a WNWESE direction of the principal stress axis sigma 1. This direction significantly diverges from the direction of regional compression, which is NNW-SSE. This deviation is here attributed to the high amount of phyllosilicates-rich layers along and in proximity of the Merano Mules line. The low frictional coefficient of 2 phyllosilicates could account for both, the weak behaviour of the Merano Mules line and a stress reorientation at its surroundings.