Zircon M257 ‐ a Homogeneous Natural Reference Material for the Ion Microprobe U‐Pb Analysis of Zircon |
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| Authors: | Lutz Nasdala Wolfgang Hofmeister Nicholas Norberg James M Martinson Fernando Corfu Wolfgang Dörr Sandra L Kamo Allen K Kennedy Andreas Kronz Peter W Reiners Dirk Frei Jan Kosler Yusheng Wan Jens Götze Tobias Häger Alfred Kröner John W Valley |
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| Institution: | 1. Institut für Mineralogie und Kristallographie, Universit?t Wien, Althanstr. 14, A‐1090 Wien, Austria;2. Institut für Geowissenschaften, Johannes Gutenberg‐Universit?t, Becherweg 21, D‐55099 Mainz, Germany;3. Sektion 4.1, Helmholtz‐Zentrum Potsdam, Deutsches Geoforschungszentrum, D‐14473 Potsdam, Germany;4. Department of Earth Science, University of California, Santa Barbara, CA 93106, USA;5. Department of Geosciences, University of Oslo, Postbox 1047 Blindern, N‐0316 Oslo, Norway;6. Institut für Geowissenschaften und Lithosph?renforschung, Justus‐Liebig‐Universit?t, D‐35390 Gie?en, Germany;7. Geozentrum, Johann‐Wolfgang‐Goethe‐Universit?t, Altenh?ferallee 1, D‐60438 Frankfurt, Germany;8. Jack Satterly Geochronology Laboratory, Department of Geology, University of Toronto, 22 Russell St., Toronto, Ontario, M5S 3B1, Canada;9. Department of Imaging and Applied Physics, Curtin University of Technology, Kent St., Bentley, 6102, Western Australia;10. Geowissenschaftliches Zentrum, Universit?t G?ttingen, Goldschmidtstrasse 1, D‐37077 G?ttingen, Germany;11. Department of Geosciences, University of Arizona, Tucson, AZ 85721, USA;12. Department of Geological Mapping, Geological Survey of Denmark and Greenland, Oster Voldgade 10, DK‐1350 Copenhagen K, Denmark;13. Department of Earth Science, University of Bergen, Allegaten 41, N‐5007 Bergen, Norway;14. Beijing SHRIMP Center, Chinese Academy of Geological Sciences, 26 Baiwanzhuang Road, 100037 Beijing, China;15. Institut für Mineralogie, TU Bergakademie Freiberg, Brennhausgasse 14, D‐09596 Freiberg, Germany;16. Department of Geology & Geophysics, University of Wisconsin, Madison, WI 53706, USA |
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| Abstract: | We introduce and propose zircon M257 as a future reference material for the determination of zircon U‐Pb ages by means of secondary ion mass spectrometry. This light brownish, flawless, cut gemstone specimen from Sri Lanka weighed 5.14 g (25.7 carats). Zircon M257 has TIMS‐determined, mean isotopic ratios (2s uncertainties) of 0.09100 ± 0.00003 for 206pb/238U and 0.7392 ± 0.0003 for 207pb/235U. Its 206pb/238U age is 561.3 ± 0.3 Ma (unweighted mean, uncertainty quoted at the 95% confidence level); the U‐Pb system is concordant within uncertainty of decay constants. Zircon M257 contains ～ 840 μg g?1 U (Th/U ～ 0.27). The material exhibits remarkably low heterogeneity, with a virtual absence of any internal textures even in cathodoluminescence images. The uniform, moderate degree of radiation damage (estimated from the expansion of unit‐cell parameters, broadening of Raman spectral parameters and density) corresponds well, within the “Sri Lankan trends”, with actinide concentrations, U‐Pb age, and the calculated alpha fluence of 1.66 × 1018 g?1. This, and a (U+Th)/He age of 419 ± 9 Ma (2s), enables us to exclude any unusual thermal history or heat treatment, which could potentially have affected the retention of radiogenic Pb. The oxygen isotope ratio of this zircon is 13.9%o VSMOW suggesting a metamorphic genesis in a marble or calc‐silicate skarn. |
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| Keywords: | zircon reference material M257 U‐Pb geochronology SIMS secondary ion mass spectrometry zircon maté riau de ré fé rence M257 U‐Pb gé ochronologie SIMS spectromé trie de masse à ions secondaires |
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