Detrital zircon U–Pb geochronology of Pennsylvanian–Permian sandstones from the Turnaicum and Meliaticum (Western Carpathians, Slovakia): provenance and tectonic implications

Abstract

The blueschist-bearing Borka Nappe regarded as a part of the Meliaticum Unit s. l. and the Turnaicum Unit in its hanging-wall were thrusted together to the north on the Inner Western Carpathians basement during the orogenic events of the Late Jurassic–Early Cretaceous. A new U–Pb sensitive high-resolution ion microprobe (SHRIMP) magmatic, as well as detrital-zircon ages were used to constrain provenance and paleogeography. The detrital-zircon age spectrum of the studied metasediments contains mainly ages of the Ediacaran–Cryogenian (550–720 Ma) and Tonian–Stenian (0.9–1.1 Ga), which correspond to the Pan-African Belt and Saharan Metacraton. Subordinate Archean ages were likely derived from the Saharan Metacraton of North Gondwana (1.7–2.2 and 2.5–2.7 Ga). The 273 ± 2 Ma zircon age of a metarhyolite, along with the youngest detrital zircon of 265 ± 4 Ma from the associated metasediments, specify the maximum depositional age of the Bucina Fm. from the Borka Nappe to the Guadalupian. The rhyolite olistoliths from the Middle/Late Jurassic Meliaticum olistostrome yielded the latest Cambrian/earliest Ordovician (488 ± 6 Ma) and Middle Ordovician (~ 465 Ma) zircon ages. This is consistent with the U–Pb zircon ages from the foot-walling Southern Gemericum basement metavolcanites, which are, therefore, regarded as a potential source. The obtained zircon ages confirm the provenance from the Southern Gemericum basement and its Permian envelope for the Meliaticum-Borka Nappe and Turnaicum sedimentary embayment.