THE HARZ MOUNTAINS (GERMANY) – CADOMIA MEETS AVALONIA AND BALTICA: U-PB AGES OF DETRITAL AND MAGMATIC ZIRCON AS A KEY FOR THE DECODING OF PANGEA´S CENTRAL SUTURE

U-Pb ages of detrital (n = 2391) and magmatic (n = 170) zircon grains from the Harz Mountains were obtained by LA-ICP-MS for provenance studies and absolute age dating (Linnemann et al. 2023). Results point to a complete closure of the Rheic Ocean at c. 419 Ma. A narrow Rhenish Seaway then re-opened in Emsian to mid-Devonian time (c. 390-400 Ma). Devonian sedimentary rocks of the Harz Mountains were deposited on the northwestern (Rheno-Hercynian) and on the southeastern (Saxo-Thuringian) margins of the Rhenish Seaway. A new U-Pb zircon age from a plagiogranite (329 ± 2) Ma within a harzburgite makes the existence of oceanic lithosphere in the Rhenish Seaway probable. The Rhenish Seaway was completely closed by Serpukhovian time (c. 328 Ma). Existence of a terrane in the seaway is not supported by the new data. Provenance studies and spatial arrangement allow reconstruction of the thin- to thick skinned obduction style of the Harz Mountains onto the southeastern margin of East Avalonia (Rheno-Hercynian Zone) during the Variscan orogeny. Detrital zircon populations define Rheno-Hercynian and Saxo-Thuringian nappes. Intrusion of the granitoid plutons of the Harz Mountains occurred in a time window of c. 300 to 295 Ma and constrained the termination of Variscan deformation (Linnemann et al. 2023).

Linnemann, U., Zweig, M., Zieger-Hofmann, M., Vietor, T., Zieger, J., Haschke, J., Gärtner, A., Mende, K., Krause, R., Knolle, F. 2023. The Harz Mountains (Germany) – Cadomia meets Avalonia and Baltica: U-Pb ages of detrital and magmatic zircon as a key for the decoding of Pangea´s central suture. In: Nance, R. D., Strachan, R. A., Quesada, C. and Lin, S. (eds) Supercontinents, Orogenesis and Magmatism. Geological Society, London, Special Publications, 542, https://doi.org/10.1144/SP542-2023-52.