Volcanites of MORB and WPB character in the evaporitic Permian Haselgebirge Formation (Eastern Alps, Austria) and possible tectonic implications

The evaporitic Haselgebirge Formation hosts in many places small occurrences of basaltic rocks. The geochemistry of these basalts can potentially provide information about the tectonic setting of the Haselgebirge Formation and the evolution of the Meliata ocean, respectively. XRD analysis and thin sections give hints to the original geochemistry, however the basalts altered significantly in contact with brines. Therefore, we present here 70 new XRF analyses of these basaltic rocks from various localities (Pfennigwiese, Annaberg, Wienern, Hallstatt, Moosegg, Lammertal) and compare the results with previous data from local studies (Gruber et al., 1991; Kirchner 1979; Kirchner 1980a; Kirchner 1980b; Kralik et al, 1984; Leitner et al., 2017; Schorn et al., 2013; Ziegler, 2014; Zirkl, 1957). Based on the concentrations of immobile trace elements (Zr, Nb, Y, Ti), a predominance of MORB-like compositions is observed for the Lower Austrian occurrences and for the locality Wienern (Grundlsee). On contrast, basalts from the localities Lammertal, Moosegg and Hallstatt have predominantly within-plate-type compositions. Both groups plot for the most part in the plume source field after Condie (2003). We discuss a striking regional (east-west) difference of basalt types in terms of existing palinspastic models for the Haselgebirge formation (Leitner et al., 2017; Stampfli & Borel, 2002; McCann et al., 2006).