Permo-Carboniferous magmatic flare-up: two supervolcanoes at 299 Ma in the North Saxon Volcanic Complex (Germany), their timing and melt sources

The North Saxon Volcanic Complex (Germany) is one of the largest exposed Permo-Carboniferous caldera systems in central Europe that includes two supervolcanoes. Contrasting age data still hinder a temporal interpretation of the volcano-sedimentary processes. We applied high-precision U-Pb chemical abrasion-isotope dilution-thermal ionization mass spectrometry to five samples covering the whole succession from the earliest volcanic members to the latest. The new ages indicate that volcanic activity lasted ca. one Myr, which is considerably shorter than previously assumed. The volcanic activity in the North Saxon Volcanic Complex belongs to the magmatic flare-up at the Permo-Carboniferous transition. Contemporaneous volcanic layers are preserved in many volcano-sedimentary basins within and north to the Bohemian Massif. A compilation of high-precision ages in these basins supports the short duration of a few Myr for the volcanic flare-up at the Carboniferous-Permian transition. The melt sources of the two studied supervolcanoes are dominated by crustal material according to new initial strontium isotope data and document an increasing mantle input towards the latest supervolcano. The Sr isotope results confirm together with published whole rock geochemical data the previously recognised north–south trend for Permo-Carboniferous volcanic rocks. Melts in the north (Oslo graben) are dominated by mantle sources, whereas towards the south approaching the Bohemian Massif crustal components contribute increasingly to magma generation. Graphical abstract