Early Carboniferous blueschist facies metamorphism in metapelites of the West Sudetes (Northern Saxothuringian Domain, Bohemian Massif)

The metamorphic evolution of micaschists in the north-eastern part of the Saxothuringian Domain in the Central European Variscides is characterized by the early high-pressure M1 assemblage with chloritoid in cores of large garnet porphyroblasts and a Grt-Chl-Phe-Qtz +/- Pg M2 assemblage in the matrix. Minerals of the M1-M2 stage were overprinted by the low-pressure M3 assemblage Ab-Chl-Ms-Qtz +/- Ep. Samples with the best-preserved M1-M2 mineralogy mostly appear in domains dominated by the earlier D1 deformation phase and are only weakly affected by subsequent D2 overprint. Thermodynamic modelling suggests that mineral assemblages record peak-pressure conditions of >= 18-19 kbar at 460-520 degrees C (M1) followed by isothermal decompression 10.5-13.5 kbar (M2) and final decompression to < 8.5 kbar and < 480 degrees C (M3). The calculated peak P-T conditions indicate a high-pressure/low-temperature apparent thermal gradient of similar to 7-7.5 degrees C km-1. Laser ablation inductively coupled plasma mass spectrometry isotopic dating and electron microprobe chemical dating of monazite from the M1-M2 mineral assemblages give ages of 330 +/- 10 and 328 +/- 6 Ma, respectively, which are interpreted as the timing of a peak pressure to early decompression stage. The observed metamorphic record and timing of metamorphism in the studied metapelites show striking similarities with the evolution of the central and south-western parts of the Saxothuringian Domain and suggest a common tectonic evolution along the entire eastern flank of the Saxothuringian Domain during the Devonian-Carboniferous periods.