The petrologic appearance of SAM (Southern limit of Alpine Metamorpism) south of the Tauern Window

SAM is an E-W trending suture within the southernmost Austroalpine basement separating Austroalpine basement rocks with highgrade Alpine metamorphic overprint towards the north from those to the south where Alpine metamorphism is lacking. It follows partly well known tectonic lines (Passeier-Jauffen line, Deffregger-Antholz- Vals line, Ragga-Teuchl line) which occur still north of the Periadriatic linement. Due to earlier petrologic work in the Ötztal basement and the Millstatt basement, to the W and E of the Tauern Window, respectively, an increasing metamorphic gradient from N towards the SAM was recorded and the paired occurrence of paragonite- amphibolites and eclogites was indicative for the transition from epidot-amphibolite-to eclogite-facies conditions. In this project it is planned to reconstruct the metamorphic conditions along SAM in the Austroalpine basement south of the Tauern Window in order to get a consistent picture of the tectonometamorphic evolution of SAM. The well exposed area of the Kreuzeck mountain range is very well suited for a comparative petrologic study of both rock units, adjacent along SAM (Ragga-Teuchl line) where the northern unit contains relictic eclogites whereas the southern unit is characterized by low pressure assemblages (andalusite). The aim is to derive the whole pressure-temperature loops of the different lithologies in both basement blocks (the northern Polinik unit and the southern Strieden unit) by means of modern geothermobarometric methods and scanning electron microscopic techniques. Furthermore it is planned to compare the chemical composition of metabasites of both units and within the suture zone by means of geochemical discrimination methods with the aim to get information about the tectonic setting of the adjacent rock units. Additionally, Sm-Nd-dating of garnet and other phases in eclogites should give further information on the exact age of this high pressure event of a probable Cretaceous age. It is the goal of this project to give a consistent picture of the tecto-nometamorphic evolution of the Austroalpine units to the north and south of SAM in order to get a better understanding of the geodynamic meaning of this dominant suture of the Eastern Alps. Finally, the interpretation of the seismic data across SAM obtained by the international TRANSALP project will be significantly supported by the exact knowledge of the surface petrology.