Location of the Rheic suture in the eastern Bohemian Massif: evidence from detrital zircon data

Abstract

Three detrital zircon concentrates from the metasediments of the Orlica-Snieznik dome, Bohemian Massif, have been dated using Sensitive High Resolution Ion Microprobe. They yielded Precambrian age spectra similar to those that are characteristic of the Cadomian terranes: (1) Archaean and Palaeoproterozoic zircons scattered between 3380 and 1860 Ma, and (2) abundant Neoproterozoic zircons dated at 770–560 Ma. Two of the analysed samples also contain Early Cambrian and Early-Late Cambrian zircons. The estimated maximum sedimentation ages are: 563 ± 6 Ma for the Mlynowiec paragneisses, 532 ± 6 Ma for the Stronie schist and 490 ± 9 Ma for the Goszów quartzite that are interpreted as three distinct metasedimentary successions. They represent a Neoproterozoic back-arc basin, Early Cambrian incipient rift basin and a Lower Ordovician post-rift succession respectively. These successions are the deformed and metamorphosed, allochthonous equivalent to the passive Saxo-Thuringian margin. They were subducted during a Variscan collision and then exhumed in front of the rigid buttress of Brunia/East Avalonia.hree detrital zircon concentrates from the metasediments of the Orlica-Śnieżnik dome, Bohemian Massif, have been dated using Sensitive High Resolution Ion Microprobe. They yielded Precambrian age spectra similar to those that are characteristic of the Cadomian terranes: (1) Archaean and Palaeoproterozoic zircons scattered between 3380 and 1860 Ma, and (2) abundant Neoproterozoic zircons dated at 770–560 Ma. Two of the analysed samples also contain Early Cambrian and Early-Late Cambrian zircons. The estimated maximum sedimentation ages are: 563 ± 6 Ma for the Młynowiec paragneisses, 532 ± 6 Ma for the Stronie schist and 490 ± 9 Ma for the Goszów quartzite that are interpreted as three distinct metasedimentary successions. They represent a Neoproterozoic back-arc basin, Early Cambrian incipient rift basin and a Lower Ordovician post-rift succession respectively. These successions are the deformed and metamorphosed, allochthonous equivalent to the passive Saxo-Thuringian margin. They were subducted during a Variscan collision and then exhumed in front of the rigid buttress of Brunia/East Avalonia.