A Permian andesitic tuff ring at Rožmitál (the Intra-Sudetic Basin, Czech Republic) – evolution from explosive to effusive and high-level intrusive activity

Abstract

Mafic, monogenetic vol ca nism is in creas ingly rec og nized as a com mon man i fes ta tion of post-collisional vol ca nism in late Variscan, Permo-Car bon if er ous intramontane bas ins of Cen tral Eu rope. Al though iden ti fi ca tion of in di vid ual erup tive cen tres is not easy in these an cient suc ces sions, the Perm ian Rožmitál andesites in the Intra-Sudetic Ba sin (NE Bo he mian Mas sif) pro vide an ex cep tion ally de tailed re cord of ex plo sive, ef fu sive and high-level in tru sive ac tiv ity. Based on field study and petrographic and geo chem i cal data on pyroclastic and co her ent rocks, the Rožmitál Suc ces sion is in ter preted as the prox imal part of a tuff ring sev eral hun dred metres in di am e ter. Ini tial ac cu mu la tion of pyroclastic fall and surge de pos its oc curred dur ing phreatomagmatic erup tions, with tran si tions to wards Strombolian erup tions. Gul lies filled with re worked tephra doc ument pe ri ods of ero sion and redeposition. Andesitic blocky lavas capped the volcaniclastic suc ces sion. In va sion of lavas into un con sol i dated sed i ments and em place ment of shal low-level in tru sions in near-vent sec tions re sulted in the for ma tion of jigsaw-and ran domly-tex tured peperites. Most geo chem i cal dif fer ences be tween co her ent andesites and pyroclastic rocks can be linked to in cor po ra tion of quartz-rich sed i ments dur ing the ex plo sive erup tive pro cesses and to later ce men ta tion of the volcaniclastic de pos its by do lo mite. The Rožmitál tuff ring could have been one of sev eral phreatomagmatic cen tres in a monogenetic vol ca nic field lo cated on an al lu vial plain.

Ambiguous isotopic and geochemical signatures resulting from limited melt interactions in a seemingly composite pluton: a case study from the Strzegom–Sobótka Massif (Sudetes, Poland)

“…Older granitoids are believed to have been generated as a result of nappe stacking that led to an increase in heat in the thickened orogenic root (e.g., Franke 2000). Younger granitoids intruded after the cessation of the Variscan convergence; the most recent granitoids are coeval with bimodal volcanism (e.g., Kryza and Awdankiewicz 2012;Awdankiewicz et al 2014;Turniak et al 2014). Thus, younger granitic plutonism could have resulted from decompression melting related to lithospheric thinning in the post-Variscan extensional regime (e.g., Henk 1997).…”

Late Palaeozoic Volcanism in Central Europe—Geoheritage Significance and Use in Geotourism

“…In the Broumovsko National Geopark, a few rather small natural outcrops of volcanic rocks are included into the webbased guide to sites of geological interest, showing all main rock types in the area (https://geopark.broumovsko.cz/ geologicke-lokality1; access date 31-10-2019; Fig. 1d), but the best exposure is a disused part of Rožmitál quarry, where andesitic lava flows and various pyroclastic deposits can be seen, recently documented by Awdankiewicz et al (2014a) (Fig. 2b).…”

“…Likewise, extensive volcanic rock outcrops in the Bohemian Paradise UNESCO Global Geopark and the Broumovsko Geopark cannot be directly linked to any original landforms from the Permian times and reconstructed palaeovolcanic landscapes are very different from those of today (e.g. Awdankiewicz et al 2014a). However, some isolated rhyolite hills in the Wałbrzych region and the Land of Extinct Volcanoes are interpreted as not very different from the original volcanic structures and the rationale for their survival was rapid burial by clastic sediments, as shown for large volcanic bodies in Central European lowland (Geißler et al 2008).…”

Towards Identification of Zircon Populations in Permo-Carboniferous Rhyolites of Central Europe: Insight from Automated SEM-Mineral Liberation Analyses

“…The Krucze sample was a part of lava/tuff sequence that has been included in a thick volcano-sedimentary fill of the Intra-Sudetic Basin. The volcanic activity in the basin predominately comprises silicic rocks (rhyodacites in Carboniferous and rhyolites in Permian) and less abundant intermediate volcanic rocks [26,27]. The volcanism is dated between 313 and 283 Ma, with the peak activity at~290 Ma.…”