Exhumation History of the Orlica Snieznik Dome, Northeastern Bohemian Massif (Poland and Czech Republic)

The Orlica-Snieznik Dome (OSD), located in the northeastern Bohemian massif (Czech Republic and Poland), represents a Variscan massif consisting of widespread amphibolite-facies gneisses and migmatites enclosing eclogite and granulite crustal-scale lenses. ⁴⁰ Ar/ ³⁹ Ar thermochronology yielded cooling ages for white mica and biotite between 341 ± 1 Ma to 337 ± 0.6 Ma and 342 ± 1 Ma to 334 ± 0.6 Ma from the Snieznik mountains. One amphibolite-derived hornblende yielded an integrated Ar-Ar age of ca. 400 Ma. The Orlica mountains yielded cooling ages between 338 ± 0.9 Ma to 335 ± 0.5 Ma. U-Th-total Pb monazite geochronology confirms two thermal events, likely commencing at ca. 400 Ma with granulite facies metamorphism. The cooling ages of the gneisses and schists are consistent across the dome and represent rapid wholesale cooling of the OSD, on an order of 50 °C/m.y. indicative of exhumation-related, amphibolite-facies metamorphism directly following UHP conditions.