Cambro-Ordovician vs Devono-Carboniferous geodynamic evolution of the Bohemian Massif: evidence fromP–T–tstudies in the Orlica–Śnieżnik Dome, SW Poland

Abstract

The pressure–temperature–deformation–time (P–T–d–t) record of metagranitic rocks and adjacent diverse rocks of the metavolcano-sedimentary group from the Orlica–Śnieżnik Dome (OSD) in SW Poland is examined. The study aims to better understand the course of the break-up of northern Gondwana and the overprinting Variscan tectonometamorphism in the NE Bohemian Massif. We test the existing hypotheses that explain the Cambro-Ordovician thermal event recorded in the meta-supracrustal group by (i) syn-deformational regional metamorphism or (ii) the contact metamorphism of the (meta)sedimentary rocks around the intruding ~490–500 Ma granitic magmas. In addition, we check the extent and timing of the Variscan prograde and retrograde medium-pressure metamorphism in the OSD. The results imply that Early Palaeozoic monazites, rarely preserved in both rock groups, document ~490–500 Ma volcanic and plutonic events related to the Gondwana's break-up and following disturbance of the Th–U–Pb system during younger, Variscan events. The monazite geochronology reveals no distinct Cambro-Ordovician thermal aureole around the post-granitic orthogneisses. However, no large-scale Variscan juxtaposition is evident between the two main OSD rock groups or within the meta-supracrustal rocks. Consistent P–T–d–t results for the meta-supracrustal rocks and the orthogneisses suggest that their precursors contacted before the Variscan tectonometamorphism. The directly contiguous ortho- and paragneisses together experienced tectonometamorphic processes at maximum depths that correspond to 7.5–8.0 kbar and maximum temperatures of ~600–620°C, as a result of the Variscan collision of Gondwana and Euramerica. The continental collision-related events intensified at ~360 Ma and ~330–340 Ma.

Provenance of the early Palaeozoic volcano-sedimentary successions from eastern part of the Central Sudetes: implications for the tectonic evolution of the NE Bohemian Massif

“…This allows us to propose a new model for the development of the Cambro-Ordovician rocks cropping out in the eastern part of the Fore-Sudetic Block from the early Palaeozoic to the Carboniferous. The model is generally consistent with those proposed for other Late Neoproterozoic and Cambro-Ordovician sequences exposed in the Bohemian Massif (Jastrzębski et al 2017;Hajná et al 2018;Collett et al 2020;Soejono et al 2020;Collett et al 2022;Soejono et al 2022). Our data combined with already published results shed new light on the development of the passive Gondwana margin and the nature of the tectonic suture separating the Central and East Sudetes.…”

“…Turniak et al 2000;Zieger et al 2018), Oberc-Dziedzic et al (2005 and Pin et al (2007) interpreted them on the basis of Sm-Nd isotopic data and bulk rock geochemistry as either typical S-type post-collisional or anorogenic and related to continental break-up. The latter idea and the relationship of the metagranitoids to continental break-up was recently supported by Jastrzębski et al (2017).…”

Syn-deformational melt percolation through a high-pressure orthogneiss and the exhumation of a subducted continental wedge (Orlica-Śnieżnik Dome, NE Bohemian Massif)

“…This implies that both lithologies shared the same process of burial to ~19-20 kbar and >700 ºC (Chopin et al 2012b;Štípská et al 2012). This contrasts with the conditions from augen orthogneiss in direct continuity with paragneiss in the synforms, which show maximum burial conditions of ~7.5-8.0 kbar and ~600-620 ºC (Jastrzebski et al 2017). Recent mineral equilibria modelling of Štípská et al (2019) reveals that the migmatitic orthogneiss types were equilibrated at ~15-17 kbar and ~690-740 ºC during infiltration of a granitic melt.…”

Rutile Mineral Chemistry and Zr-in-Rutile Thermometry in Provenance Study of Albian (Uppermost Lower Cretaceous) Terrigenous Quartz Sands and Sandstones in Southern Extra-Carpathian Poland

“…The Bohemian Massif comprises a large variety of igneous and metamorphic rocks [100,101]. Therefore, it is possible to indicate potential source rocks for detrital rutile crystallized under amphibolite-LT eclogite facies (e.g., mica schists, gneisses) conditions [100,102,103], as well as in high-grade granulite-HT eclogite facies rocks, namely granulites and gneisses [101,104,105]. During the Albian, the Bohemian Massif was neighboring to the western and central zones (Figure 2).…”