Structural position of high-pressure felsic to intermediate granulites from NE Moldanubian Domain (Bohemian Massif)

• Published in: Journal of the Geological Society Vol. 167; no. 2; pp. 329 - 345
• Main Authors: Tajcmanova, L, Soejono, I, Konopasek, J, Kosler, J, Klötzli, U
• Format: Journal Article
• Language: English
• Published: London, UK Geological Society of London 01-03-2010; The Geological Society of London; Geological Society; Geological Society Publishing House
• Subjects: absolute age; Bohemian Massif; Carboniferous; Central Europe; Crystalline rocks; Czech Republic; dates; deformation; Dinantian; Earth sciences; Earth, ocean, space; electron probe data; Europe; Exact sciences and technology; exhumation; felsic composition; Geology; granulites; high pressure; ICP mass spectra; igneous and metamorphic rocks; Igneous and metamorphic rocks petrology, volcanic processes, magmas; mass spectra; metamorphic rocks; Moldanubian; Moravia; P-T-t paths; Paleozoic; Pb/Pb; Petrology; phase equilibria; phosphates; Plate tectonics; Policka Complex; polyphase processes; pressure; spectra; Structural geology; Svratka Dome; tectonics; thermal history; thermal ionization mass spectra; U/Pb; Variscides; xenotime; Central Europe; Europe; Bohemian Massif; laser methods; gneisses; schists; granulites; Precambrian; isotope dilution; metaplutonic rocks; mineral assemblages; xenotime; crustal blocks; zircon; temperature; silicates; deformation; paragneiss; dating; tectonics; nesosilicates; models; metaigneous rocks; micaschist; Moldanubian; exhumation; ablation; lower crust; pressure; U/Pb; metamorphic rocks; high pressure; lead; phosphates; inductively coupled plasma; orogeny; metagranite
• ISSN: 0016-7649; 2041-479X
• DOI: 10.1144/0016-76492009-086

At the northeastern edge of the Moldanubian Zone, a large body of felsic to intermediate granulite with relics of high-pressure mineral assemblage is exposed within medium-grade paragneisses, micaschists and metagranites. A polyphase tectonic evolution in the study area resulted in three deformation phases (D1-D3). Peak metamorphic conditions (860-1000°C and 16 kbar) in granulites are interpreted as reflecting an early stage of the high-grade evolution of the orogenic lower crust. These conditions were followed by exhumation of the orogenic lower crustal block to mid-crustal levels (6-8 kbar). In contrast to this, the study of metamorphic conditions in the surrounding micaschists (660°C and 8 kbar) shows that these rocks never experienced pressures and temperatures of the orogenic lower crust. Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) U-Pb dating of zircon from the granulite yielded a concordia age of 354±7 Ma, whereas the conventional isotope dilution thermal ionization mass spectrometry (ID-TIMS) and LA-ICP-MS dating of xenotime gave identical concordia ages of 336.2±1.2 and 339±3 Ma, respectively. Combination of new structural and petrological results with LA-ICP-MS zircon and xenotime dating leads to development of a well-constrained exhumation model and brings new insights into the behaviour of lower crustal rocks during orogenesis.