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Metamorphic overprint of Neoproterozoic greywackes from the Lausitz Anticline and North Saxon Anticline (Saxo-Thuringia, Germany): timing and metamorphic conditions

Greywackes represent a substantial part of the Cadomian basement of Saxo-Thuringia. The trigger for the widespread contact metamorphic, Cadomian overprinting of the greywackes investigated here, is assumed to have been caused by early Cambrian intrusions (c. 540 Ma; Linnemann 2007, Geol. Soc. London Spec. Publ., 286, 35–51). Here we present for the first time a multi-method approach, using electron microprobe U–Th–Pb analyses of monazites, K–Ar fine-fraction analyses and the illite crystallinity of suitable samples from the Lausitz Anticline and North Saxon Anticline to obtain information on the age and degree of metamorphic overprint. Petrographic investigations show that the studied greywackes have only experienced slight metamorphic overprint. The age dating did not detect a Cadomian influence (540–530 Ma). Rather, the ages are locally very different. In some of the samples, the data reveal multi-stage thermal events. Late Cambrian monazite ages could be associated with the transition from the Cadomian orogeny to the opening of the Rheic Ocean. Early Ordovician monazite and sporadic Late Ordovician monazite and K–Ar ages also occur. Their meaning regarding a thermal event is a matter of debate. Some K–Ar ages of c. 314–294 Ma and monazite age of c. 280 Ma are clearly associated with the processes of the high-temperature metamorphism and most probably, the post-tectonic granites of the Variscan orogeny. The youngest monazite age from the Jurassic in one of the samples could be related to the hydrothermal activity observed in Central Europe during that time.

Details

Author
Victoria Kühnemann1, Guido Meinhold1, Bernhard Schulz1, Sabine Gilbricht1, Sebastian Weber2, Klaus Wemmer3
Institutionen
1TU Bergakademie Freiberg, Germany; 2Sächsisches Landesamt für Umwelt, Landwirtschaft und Geologie (LfULG), Germany; 3Georg-August-Universität, Germany
Veranstaltung
GeoSaxonia 2024
Datum
2024
DOI
10.48380/9hej-fp60