Oligocene emplacement of the Eclogite Zone of the central Tauern Window, Eastern Alps, Austria

Abstract

The EZ is an approximately 20km long and 2–3km wide coherent unit of the Tauern Window in the Eastern Alps. It is sandwiched between the Venedigerand the Glockner Nappe. While rocks in the EZ experienced HP metamorphic conditions (24 kbar/650°C), rocks from the underlying Venediger Nappe and the overlying Glockner Nappe only record lower alpine metamorphic conditions with peak pressures not exceeding 10 and 8 kbar, respectively. While metamorphism in the EZ is well dated with an average age of 31.5±0.7Ma (Glodny et al. 2005) the final emplacement of these different nappes is still under debate. Our Rb-Sr-data indicate that top-N thrusting at the base and large-scale folding of the EZ was coeval with sinistral strike-slip faulting at its upper boundary and eclogite-facies metamorphism in the EZ. The data also indicate that today’s nappe architecture must have been established in less than 2Ma after the eclogite facies metamorphism in the EZ. Very fast exhumation of the EZ was accomplished in a transpressional setting, which might explain why the exposed EZ is such a small unit.