Variscan tectonism in the Eastern Alps: Insights from the Schladming Complex in the Austroalpine mega-unit

The last known supercontinent, Pangea, formed through the Variscan orogeny as the result of closure of Rheic ocean and collision between Gondwana and Laurussia. The Schladming Complex is the key part of the arc-like Silvetta-Gleinalpe basement of the Austroalpine Unit in the Eastern Alps (Neubauer et al., 2022). The Devonian to Carboniferous magmatism/metamorphism in the Schladming Complex record the Variscan orogeny that collision between Laurasia and assembly of Paleo-Adria and Galatian terranes (Neubauer et al., 2022). The continental arc like granitic gneisses in the southeast Schladming Complex have protolith ages of 485 – 483 Ma, and records the three metamorphic ages: ca. 420 Ma, ca. 380 Ma, and ca. 350 Ma. In addition, subduction related hornblendites, amphibolites, and granites have crystallization ages of 380 – 350 Ma, and host the metamorphic ages of 330 – 300 Ma. Therefore, our new data of Schladming Complex reveal three Variscan stages in the Eastern Alps: an early stage at ~ 420 – 380 Ma, high-grade metamorphism at ~380 – 330 Ma, and second metamorphism at ~330 – 300 Ma.To sum up, we combine the regional geological evidences, geochemical features and distribution characteristics of the samples, to reconstruct tectonic evolution history of the Eastern Alps during the Devonian to Late Corboniferous. The subduction and rollback of the Rheic Ocean crust led to opening of the Paleo-Tethys Ocean and its brunch ocean (Balkan-Carpathians ocean) in the Early Devonian (~420 Ma; Guan et al., 2025). In the Late Devonian (~380 Ma), with the southward subduction of the Rheic Ocean and the northward subduction of Paleo-Tethys Ocean, the Eastern Alps and the Western Carpathians in extension setting and instruded by instensive continental arc-related magma. The Tournaisian (~350 Ma) magmatism marking the initial closure of Balkan-Carpathians ocean, which cause collision between the Paleo-Adria and the Galatia hosting Schladming. After Tournaisian (~350 Ma), the Paleo-Adria and the Galatia initially collided with the Laurasia, which marking the closure of Rheic Ocean and beginning of Variscan orogeny, followed by syn-collision stage in the Late Carboniferous. Our study suggest that the basement of Eastern Alps had been strongly overprinted by the Variscan orogeny. ReferencesGuan, Q.B., Liu, Y.J., Neubauer, F., Genser, J., Chang, R.H., Liu, B.R., Li, S.Z., Huang, Q.W., Yuan, S.H., 2025. Early Paleozoic subduction initiation in the West Proto-Tethys Ocean: Insights from ophiolitic Speik Complex in the Eastern Alps. Geoscience Frontiers 16, 102121. https://doi.org/10.1016/j.gsf.2025.102121Neubauer, F., Liu, Y.J, Dong, Y.P., Chang, R.H., Genser, J., Yuan, S.H., 2022. Pre-Alpine tectonic evolution of the Eastern Alps: From Prototethys to Paleotethys. Earth-Science Reviews 226, 103923. https://doi.org/10.1016/j.earscirev.2022.103923