caa a22 4500 445390034 CHVBK 20180317143043.0 cr unu---uuuuu 170323e20111001xx s 000 0 eng 10.1007/s00710-011-0162-x doi (NATIONALLICENCE)springer-10.1007/s00710-011-0162-x Timing of Variscan HP-HT metamorphism in the Moldanubian Zone of the Bohemian Massif: U-Pb SHRIMP dating on multiply zoned zircons from a granulite from the Dunkelsteiner Wald Massif, Lower Austria [Elektronische Daten] [Gertrude Friedl, Rob Cooke, Friedrich Finger, Neal McNaughton, Ian Fletcher] In an attempt to better constrain the timing of Variscan HP-HT metamorphism in the SE Bohemian Massif we have dated zoned zircons from a garnet-kyanite granulite of granitic composition from the Dunkelsteiner Wald Massif, Lower Austria, by means of sensitive high-resolution ion microprobe (SHRIMP) technique. In order to combine isotopic information with crystal growth textures, CL and BSE images were systematically taken from the dated zircons. A characteristic threefold concentric zoning was found in many zircons. This involves pre-Variscan protolithic cores followed by two distinct metamorphic/anatectic overgrowth shells of Variscan age. The inner overgrowth shell is characterized by a weak CL but bright BSE signal, and yields high contents of uranium (0.1 to 0.2 wt.%). A pooled U-Pb Concordia age for this zone is 342.0 ± 3.0Ma (n = 11, MSWD = 0.12). The second, outer, overgrowth shell is always bright in the CL image, dark in the BSE image, and has generally low uranium contents (mostly <500ppm). A pooled U-Pb Concordia age for this zone is 337.1 ± 2.7Ma (n = 11, MSWD = 0.22). These results imply that the Variscan HT crystallisation history of the Moldanubian granulites took place over a period of a few million years and was not an extremely rapid subduction-exhumation process. SHRIMP measurements in the protolithic cores yield a cluster of (sub)concordant ages between ∼390 and 460Ma and a few outliers at higher ages mostly represented by cores in cores. Core domains, which are large, homogeneous and with undisturbed igneous oscillatory zoning, yielded preferentially ages between 430 and 460Ma. We therefore consider that granitic protolith formation took place at that time. The still older inner cores are interpreted as inherited into the granitic melt. Springer-Verlag, 2011 Friedl Gertrude Department of Geography and Geology, University of Salzburg, Hellbrunnerstraße 34, 5020, Salzburg, Austria aut Cooke Rob Soil Mechanics, Askern Road, Carcroft, DN6 8DG, Doncaster, UK aut Finger Friedrich Department of Materials Engineering and Physics, University of Salzburg, Salzburg, Austria aut McNaughton Neal Centre for Global Metallogeny, School of Earth and Geographical Sciences, The University of Western Australia, Perth, Australia aut Fletcher Ian Centre for Global Metallogeny, School of Earth and Geographical Sciences, The University of Western Australia, Perth, Australia aut Mineralogy and Petrology Springer Vienna 102/1-4(2011-10-01), 63-75 0930-0708 102:1-4<63 2011 102 710 https://doi.org/10.1007/s00710-011-0162-x text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1007/s00710-011-0162-x text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Friedl Gertrude Department of Geography and Geology, University of Salzburg, Hellbrunnerstraße 34, 5020, Salzburg, Austria aut NATIONALLICENCE 700 1- Cooke Rob Soil Mechanics, Askern Road, Carcroft, DN6 8DG, Doncaster, UK aut NATIONALLICENCE 700 1- Finger Friedrich Department of Materials Engineering and Physics, University of Salzburg, Salzburg, Austria aut NATIONALLICENCE 700 1- McNaughton Neal Centre for Global Metallogeny, School of Earth and Geographical Sciences, The University of Western Australia, Perth, Australia aut NATIONALLICENCE 700 1- Fletcher Ian Centre for Global Metallogeny, School of Earth and Geographical Sciences, The University of Western Australia, Perth, Australia aut NATIONALLICENCE 773 0- Mineralogy and Petrology Springer Vienna 102/1-4(2011-10-01), 63-75 0930-0708 102:1-4<63 2011 102 710 Metadata rights reserved Springer special CC-BY-NC licence nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-springer