Pb Ages of Detrital Zircons In Relation To Geodynamic Evolution: Paleozoic of the Northern Gemericum (Western Carpathians, Slovakia)

Abstract

Abstract New U-Pb sensitive high-resolution ion microprobe (SHRIMP) detrital-zircon ages from early Paleozoic to Permian siliciclastic metasediments are used to constrain provenance and paleogeographic affinity of the Northern Gemericum Unit (NGU) in the Western Carpathians (Central Europe). The samples span the time period from ∼ 480 Ma to ∼ 260 Ma and permit the recognition of provenance changes that reflect the realm's geodynamic evolution. The detrital-zircon age spectrum of one early Paleozoic sample resembles the Neoproterozoic and Archean ages of the Cadomian belt (550–650 Ma) and the West African craton provenances (1.8–2.7 Ga). The origin of the early Paleozoic NGU (Rakovec) basin is inferred to be the rifting as followed by back-arc spreading which occurred at the Cambrian–Ordovician boundary (ca. 480 Ma), as continental pieces started to split off from the Gondwanan margin. The deformation and closure of the early Paleozoic basin is coincident with the 355 Ma peak of the post-Tournaisian detrital-zircon age assemblage. The detrital-zircon age spectra of two post-Mississippian and two post-Artinskian samples indicate high exhumation and erosion rates in the Variscan collision belt. Pennsylvanian–Permian sedimentary troughs, formed between 318 and 275 Ma, record contemporaneous unroofing of the Variscan collision belt and magmatic activity during post-orogenic transtensional tectonics. Zircon age spectra reflect these three Paleozoic (480–419 Ma, 340–380 Ma, 320–275 Ma) tectono-thermal events and permit the recognition of provenances, both of which supporting the interpreted changes in geotectonic regime from Ordovician rifting to Variscan compression and the subsequent extension. The zircon age data constrain the provenance linkage of the low-grade NGU basement to the Cadomian fragments within the West-European Variscides.