The continental crust of the Austroalpine Domain : the record of multiple rejuvenation of an orogenic scar

In the Alpine continental crust structural, metamorphic, sedimentary and igneous signatures indicate that orogenic scars are weak lithospheric zones of recurring tectonic and metamorphic rejuvenation during successive convergent and divergent plate dynamics. Fortunately, the overprint related to Alpine subduction and collision in the Austroalpine domain has not completely erased the markers of the transition from Variscan convergence to Permian – Triassic lithospheric thinning, making this domain a key repository to investigate the recycling of passive margins in subduction environments. Due to the fact that subduction–collision zones are characterized by the amalgamation and disaggregation of lithospheric slices, in these domains the determination of contours for thermally and structurally characterized units is crucial to accurately exploit the rock memory (i), and define the variations in sizes of crustal slices involved in the dynamic evolution of an active margin (ii). The dimensions of these structural entities evolve over time and can be reconstructed using the structural and metamorphic evolution of the basement rocks as tracers. These tectono-metamorphic units (TMUs) represent discrete portions of the orogenic crust influenced by a sequence of metamorphic and textural changes and their translational trajectories and shape changes can be derived from a joint reconstruction of quantitative P-T-d-t paths. This analytical approach offers the opportunity to test the physical compatibilities of the interconnected variables constraining numerical modelling, such as density, viscosity, and heat transfer, with structural, petrologic and geochronological data. Comparison between modelling predictions and natural data, obtained by this analytical approach, helped to solve longstanding ambiguities on the pre-Alpine and Alpine geodynamic evolution of Central and Western Austroalpine units and to explore the crustal levels of protolith derivation.