ALBERT

Description: The correlation of late Palaeozoic eruption centres situated at the northwestern margin of the Erzgebirge (Saxothuringian Zone, Germany) with the regional post-Variscan magmatism has as yet remained unresolved. Our study focuses on the petrography, geochemistry, and the formation age of the Obermühlbach volcano as one of these eruption centres. The outcropping and drilled, potassium-rich, volcanic rocks originate from a highly differentiated, calc-alkaline, peraluminous A-type granitic melt with intra-plate signature. The Obermühlbach tuff bear strong geochemical similarity to the Lower Permian Zeisigwald tuff in the near-by Chemnitz Basin. LA-ICP-MS U-Pb zircon dating of the Obermühlbach tuff and rhyolite clasts contained therein has yielded ages of 302.8 ± 3.8 Ma and 314.6 ± 2.4 Ma, respectively. Zircon saturation models suggest a temperature range of 750–800 °C for zircon crystallisation in the subvolcanic Obermühlbach rhyolites, and of ~840 °C in rhyolite clasts intercalated within the Obermühlbach tuff. The Obermühlbach tuff itself records zircon saturation temperatures in both aforementioned temperature ranges, based on different samples. The rhyolite clasts and the volcanic/sub-volcanic rocks of the Flöha Basin are similar in petrography and geochemistry. The new evidence allows a better understanding of the evolution of the Obermühlbach volcano and discloses its correlation with the regional Permo-Carboniferous magmatism.