We investigated the geochemistry of ca. 50 volcanic rock samples collected in various regions of the ca. 250 Ma old evaporite-bearing Austroalpine Haselgebirge Formation. The rocks are interpreted to represent synsedimentary volcanism in the Haselgebirge Formation. Open system low-T alteration processes have severely altered potassium, sodium, and calcium contents. However, based on immobile trace elements such as Zr, Y, Nb, Ti, the Haselgebirge volcanism can be classified as mainly basaltic. Different mantle sources must have been at play. Volcanism in the eastern part of the Haselgebirge Formation (Annaberg, Pfennigwiese) was MORB-like and probably related to asthenospheric mantle upwelling. As opposed to this, the volcanic samples of the western Haselgebirge Formation (Hallstatt, Lammertal) display predominantly alkali-basaltic trace element characteristics. It is hypothesized that they represent magmas from a metasomatized lithospheric mantle. Finally, a third basalt type with remarkably low Nb and Ta contents could be identified in the locality Wienern. It might be related to a (remnant?) subduction-modified mantle source. Our research highlights a gradual change of the type of magmatic activity in the Austroalpine Unit during the Permian. While according to literature data, magmatism in the early and middle Permian was dominantly felsic (granitic) and crustal, mafic mantle magmatism apparently gained increasing importance by the end of the Permian. This likely mirrors the beginning break-up of the local Pangea crust and the upwelling of asthenospheric mantle antedating the Triassic opening of the Meliata ocean. The observed source variations within the Haselgebirge volcanism point to a comparably greater degree of lithosphere thinning in the east. This accords with geological models where the (Triassic) Meliata ocean gained its greatest width in the Carpathian realm while wedging out towards the western Eastern Alps.