Isotopic dating of minerals from high-pressure rocks exposed along the northern Saxothuringian paleo-suture in the Bohemian Massif revealed a diachronous metamorphism of various rock types now associated within thrust sheets representing the Devonian–Carboniferous subduction–accretionary complex. Blueschists of the middle thrust sheet yielded a Lu–Hf garnet–whole rock age of 363.9 ± 1.3 Ma. The blueschists occur within garnet-free phyllites. Monazite extracted from this rock-type yielded a U–Pb ID–TIMS age of 336.5 ± 0.5 Ma. Garnet-bearing micaschist of the lower thrust sheet contains monazite, which yielded a U–Pb SIMS age of 341 ± 3 Ma, equivalent to Lu–Hf garnet-whole rock ages of 344.5 ± 1.3 and 342 ± 7 Ma obtained from the same rock type.
Existing tectonic models of the Bohemian Massif assume that the period of oceanic subduction was terminated at c. 380–375 Ma by the arrival of an attenuated Saxothuringian continental crust, which was partly subducted underneath the overriding Teplá–Barrandian Domain. However, our data suggest that the initial collision was probably caused by arrival of a smaller crustal block present within the Saxothuringian oceanic domain. After its subduction and relamination, the oceanic subduction was re-established and terminated by later collision of the Saxothuringian passive margin at c. 345–335 Ma.