High- and ultrahigh-pressure rock exhumation and tectonic structure of the southeastern Austroalpine crust

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The Austroalpine Superunit is a pile of allochthonous thrust sheets in the Eastern Alps, forming the upper plate during Paleogene southward subduction of the Penninic ocean and the following collision with Europe. Earlier, at 100 to 90 Ma, parts of the Austroalpine were affected by subduction-related metamorphism up to ultrahigh pressures (e.g., diamond-bearing gneisses). This metamorphism affected thinned continental crust in a southeast-dipping subduction zone. The exhumation of these rocks (~90 to 80 Ma) is not yet understood in terms of kinematics and mechanics but of crucial importance for the tectonic evolution of the Eastern Alps, their crustal and lithospheric geometry, and their relationships with the Carpathians, Dinarides, and Pannonian Basin.We will study exhumation of the Saualpe-Koralpe-Pohorje Complex (SKPC), the most deeply subducted part of the Austroalpine, combining outcrop-scale structural and strain analysis, as well as microstructural and texture analysis using electron-backscatter diffraction (EBSD) and time-of-flight neutron diffraction. Thereby we will investigate the deformation path and the geometry and distribution of strain accumulated during exhumation and test the hypothesis that the SKPC was extruded from the subduction zone by localized, non-cylindrical flow. We will reconstruct the geometry of the SKPC and stepwise retrodeform its exhumation. We will incorporate our results into a 3D geometric model of the Eastern Alps. Based on these results we will interpret the deep crustal and lithospheric structure in the Eastern part of the Alps and the transition into the Carpathians and Dinarides, in close collaboration with other projects within the SPP that deal with the metamorphic evolution of the SKPC and the deep lithospheric structure of the Eastern Alps.