Cliff, RA, Oberli, F, Meier, M et al. (2 more authors) (2015) Syn-metamorphic folding in the Tauern Window, Austria dated by Th-Pb ages from individual allanite porphyroblasts. Journal of Metamorphic Geology, 33 (4). 427 - 435. ISSN 0263-4929
Abstract
High-precision 232Th-208Pb dates have been obtained from allanite porphyroblasts that show unambiguous microstructural relationships to fabrics in a major syn-metamorphic fold in the SE Tauern Window, Austria. Three porphyroblasts were analysed from a single garnet mica schist from the Peripheral Schieferhülle in the core of the Ankogel Synform, one of a series of folds which developed shortly before the thermal peak of Alpine epidote-amphibolite facies metamorphism: allanite grain 1 provided two analyses with a combined age of 27.7 ± 0.7 Ma; grain 2, which was slightly bent and fractured during crenulation, provided two analyses with a combined age of 27.7 ± 0.4 Ma; a single analysis from grain 3, which overgrew an already crenulated fabric, gave an age of 28.0 ± 1.4 Ma. The five 232Th-208Pb ages agree within error and define an isochron with an age of 27.71 ± 0.36 Ma (95% confidence level; MSWD = 0.46). The results imply that the crenulation event was in progress in a short interval (<1 Ma) c. 28 Ma, and that the Ankogel Synform was forming at this time. The thermal peak of regional metamorphism in the SE Tauern Window was probably attained shortly after 28 Ma, only c. 5 Ma after eclogite facies metamorphism in the central Tauern Window. Metasediment may contain allanite porphyroblasts with clear-cut microstructural relationships to fabric development and metamorphic crystallization; for such rocks, 232Th-208Pb dating on microsamples offers a powerful geochronological tool.
Metadata
Item Type: | Article |
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Authors/Creators: |
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Copyright, Publisher and Additional Information: | © 2015, John Wiley & Sons Ltd. This is the peer reviewed version of the following article: Cliff, R. A., Oberli, F., Meier, M., Droop, G. T. R. and Kelly, M. (2015), Syn-metamorphic folding in the Tauern Window, Austria dated by Th–Pb ages from individual allanite porphyroblasts. Journal of Metamorphic Geology, 33: 427–435. doi: 10.1111/jmg.12127, which has been published in final form at http://dx.doi.org/10.1111/jmg.12127. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving. |
Keywords: | Allanite; Tauern Window; U-Th-Pb geochronology |
Dates: |
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Institution: | The University of Leeds |
Academic Units: | The University of Leeds > Faculty of Environment (Leeds) > School of Earth and Environment (Leeds) |
Depositing User: | Symplectic Publications |
Date Deposited: | 28 Aug 2015 15:38 |
Last Modified: | 04 Apr 2016 03:16 |
Published Version: | http://dx.doi.org/10.1111/jmg.12127 |
Status: | Published |
Publisher: | Wiley |
Identification Number: | 10.1111/jmg.12127 |
Open Archives Initiative ID (OAI ID): | oai:eprints.whiterose.ac.uk:85153 |