Petrochronology with Th-U-Pb monazite dating in the Zone of Erbendorf-Vohenstrauß (Saxothuringian Allochthon, NE-Bavaria)

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The Zone of Erbendorf-Vohenstrauß (ZEV) at the western margin of the Bohemian Massif is part of the Upper Allochthonous Domain in the Saxothuringian Zone of the Variscan Orogen. The ZEV and the adjacent Moldanubian Zone with their metamorphic and magmatic rocks were the target region of the Continental Deep Drilling Program (KTB). Intense geological-petrological and radiochronological (U-Pb zircon, K-Ar, Ar-Ar, Rb-Sr) have been performed there previous to 1995. Carboniferous, Devonian and Ordovician metamorphic events have been reported from the region. The Th-U-Pb dating of the accessory mineral monazite ((LREE, Th, U, Si, Ca)PO4) by electron probe microanalyser (EPMA-Th-U-Pb) in micaschists and orthogneisses now will be newly applied there. This method allows to resolve several thermal events in polymetamorphic terrains. By the in situ analysis of monazite in microstructures, analysis of Y in garnet by LA-ICP-MS and geothermobarometry, distinct segments of the pressure-temperature (P-T) paths can be related to time sections in single samples (Petrochronology). Particularly the distribution and character of the Ordovician metamorphism previous to the Variscan continental collision is a target of the investigation.