Structural studies of Alpine eclogites as a contribution to understanding the exhumation of high-pressure rocks

During the Alpine orogenesis large volumina of both oceanic and continental crust have been subducted. Most of these materials have been assimilated in the mantle; some have been exhumed from depths of even 100 km back to the surface and are exposed as high-pressure metamorphic rocks. Many models for the exhumation of high- pressure (HP) rocks have been proposed, which may be applied to the Alps. Buoayancy forces are related to differences in rock-density, and are important for the exhumation of HP units that were derived from continental lithosphere. This requires, that eclogites, which have high densities, are enclosed within light, acidic crustal rocks, which again are surrounded by heavy rocks of the earths mantle. Other models assume extensional tectonics for causing exhumation subsequent to subduction. However, most of the extensional structures which overprint the HP- related structures have formed at amphibolite to greenschist facies metamorphic conditions. This implies, that the HP units have already been exhumed for a certain amount before. A third group of models assumed material flow within the accretionary wedge, which is constrained by the geometry of the subduction channel between the upper and the lower plate ("corner flow"). However, these cannot not be used adequately to explain the exhumation of oceanic lithosphere, which has been subducted to mantle depth and affected by HP metamorphic conditions. This project focusses on detailed structural field investigations, as well as microstructural, textural, and petrological analyses in order to explain the processes of exhumation of high-pressure rocks in the Alpine orogen.