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

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Authors
Nasdala, L.
Corfu, F.
Schoene, B.
Tapster, S.
Wall, C.
Schmitz, M.
Ovtcharova, M.
Schaltegger, U.
Kennedy, Allen
Kronz, A.
Reiners, P.
Yang, Y.
Wu, F.
Gain, S.
Griffin, W.
Szymanowski, D.
Chanmuang, C.
Ende, M.
Valley, J.
Spicuzza, M.
Wanthanachaisaeng, B.
Giester, G.
Date
2018
Type
Journal Article

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Nasdala, L. and Corfu, F. and Schoene, B. and Tapster, S. and Wall, C. and Schmitz, M. and Ovtcharova, M. et al. 2018. GZ7 and GZ8 – Two Zircon Reference Materials for SIMS U-Pb Geochronology. Geostandards and Geoanalytical Research.
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Geostandards and Geoanalytical Research
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John de Laeter Centre
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Abstract

© 2018 The Authors. Geostandards and Geoanalytical Research published by John Wiley & Sons Ltd on behalf of International Association of Geoanalysts 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 mean206Pb/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.