GZ7 and GZ8 – Two Zircon Reference Materials for SIMS U-Pb Geochronology

Lutz Nasdala, Fernando Corfu, Blair Schoene, Simon R. Tapster, Corey J. Wall, Mark D. Schmitz, Maria Ovtcharova, Urs Schaltegger, Allen K. Kennedy, Andreas Kronz, Peter W. Reiners, Yue Heng Yang, Fu Yuan Wu, Sarah E.M. Gain, William L. Griffin, Dawid Szymanowski, Chutimun Chanmuang N., Martin Ende, John W. Valley, Michael J. SpicuzzaBhuwadol Wanthanachaisaeng, Gerald Giester

Research output: Contribution to journalArticle

7 Scopus citations

Abstract

Here, we document a detailed characterisation of two zircon gemstones, GZ7 and GZ8. Both stones had the same mass at 19.2 carats (3.84 g) each; both came from placer deposits in the Ratnapura district, Sri Lanka. The U-Pb data are in both cases concordant within the uncertainties of decay constants and yield weighted mean 206Pb/238U ages (95% confidence uncertainty) of 530.26 Ma ± 0.05 Ma (GZ7) and 543.92 Ma ± 0.06 Ma (GZ8). Neither GZ7 nor GZ8 have been subjected to any gem enhancement by heating. Structure-related parameters correspond well with the calculated alpha doses of 1.48 × 1018 g−1 (GZ7) and 2.53 × 1018 g−1 (GZ8), respectively, and the (U-Th)/He ages of 438 Ma ± 3 Ma (2s) for GZ7 and 426 Ma ± 9 Ma (2s) for GZ8 are typical of unheated zircon from Sri Lanka. The mean U mass fractions are 680 μg g−1 (GZ7) and 1305 μg g−1 (GZ8). The two zircon samples are proposed as reference materials for SIMS (secondary ion mass spectrometry) U-Pb geochronology. In addition, GZ7 (Ti mass fractions 25.08 μg g−1 ± 0.18 μg g−1; 95% confidence uncertainty) may prove useful as reference material for Ti-in-zircon temperature estimates.

Original languageEnglish (US)
Pages (from-to)431-457
Number of pages27
JournalGeostandards and Geoanalytical Research
Volume42
Issue number4
DOIs
StatePublished - Dec 2018

Keywords

  • SIMS
  • Ti-in-zircon geothermometry
  • U-Pb geochronology
  • reference material
  • zircon

ASJC Scopus subject areas

  • Geology
  • Geochemistry and Petrology

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    Nasdala, L., Corfu, F., Schoene, B., Tapster, S. R., Wall, C. J., Schmitz, M. D., Ovtcharova, M., Schaltegger, U., Kennedy, A. K., Kronz, A., Reiners, P. W., Yang, Y. H., Wu, F. Y., Gain, S. E. M., Griffin, W. L., Szymanowski, D., Chanmuang N., C., Ende, M., Valley, J. W., ... Giester, G. (2018). GZ7 and GZ8 – Two Zircon Reference Materials for SIMS U-Pb Geochronology. Geostandards and Geoanalytical Research, 42(4), 431-457. https://doi.org/10.1111/ggr.12239