Obervendischer und unterordovizischer Magmatismus im Bayerischen Wald

Abstract

U-Pb-SHRIMP dating of zircons, zircon morphology, geochemistry and isotopic data of metamagmatites from the Bayerischer Wald (Germany) reveal a complex evolution of this section of the Moldanubian Zone exposed in the western Bohemian Massif of the central European Variscan belt. In the south-western part of the Bayerischer Wald Upper Vendian magmatism is constrained by SHRIMP ages of 555 ± 12, 549 ± 7 and 549 ± 6 Ma from metarhyolites and a metabasite. Inherited zircon cores were not observed. Zircon overgrowths yielding pooled ages of 316 ± 10 and 319 ± 5 Ma provide evidence for Variscan metamorphic zircon growth; cathodoluminescence imaging reveals a two-stage metamorphic overprint. In contrast, Lower Ordovician magmatism and anatexis are documented in the north-eastern parts of the Bayerischer Wald by metagranitoids (480 ± 6, 486 ± 7 Ma) and a leucosome (491 to 457 Ma). Inherited zircon cores are found in Lower Ordovician metamagmatites indicating a Palaeoproterozoic-Archaean (2.70, 2.02 Ga) source region, presumably of Gondwana affinity (West African craton), and documenting Cadomian magmatism (>615 to 560 Ma). Upper Vendian magmatism is assumed at an active continental margin with ensialic back-arc development (εNd(t) –4.58 to +1.22). An active continental margin setting, possibly with some lateral variation (accretion/collision) is envisaged for the Lower Ordovician producing granitoids, rhyolites, leucosomes (εNd(t) -0.5 to -6.27) and andesites. A tentative palaeogeographic reconstruction puts the "Bayerischer Wald" in a close relationship with the Habach terrane (proto-Alps), as the "eastern" extension of terranes of the northern Gondwana margin.

• Item Type: Thesis (Dissertation, LMU Munich)
• Keywords: Moldanubikum, Bayerischer Wald, Zirkon-SHRIMP-Datierung, Geochemie, Kathodolumineszenz
• Dewey Decimal Classification: 600 Natural sciences and mathematics; 600 Natural sciences and mathematics > 550 Earth sciences
• Faculties: Faculty of Geosciences
• Language: German
• Date Accepted: 17. June 2003
• 1. Referee: Höll, Rudolf
• Persistent Identifier (URN): urn:nbn:de:bvb:19-35597
• Signature of the printed copy: 0001/UMC 13424