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GZ7 and GZ8 – Two Zircon Reference Materials for SIMS U‐Pb Geochronology.
- Source :
- Geostandards & Geoanalytical Research; Dec2018, Vol. 42 Issue 4, p431-457, 27p
- Publication Year :
- 2018
-
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. Key Points: We document a detailed characterisation of the Sri Lankan zircon gemstones GZ7 and GZ8 and propose them as SIMS U‐Pb reference materials. Both specimens have high mean U mass fractions and concordant Cambrian (GZ7) and Ediacaran (GZ8) U‐Pb ages. In addition, GZ7 is proposed as a reference material for Ti‐in‐zircon temperature estimates. [ABSTRACT FROM AUTHOR]
- Subjects :
- SECONDARY ion mass spectrometry
ZIRCON
GEMS & precious stones
LEAD
DATA analysis
Subjects
Details
- Language :
- English
- ISSN :
- 16394488
- Volume :
- 42
- Issue :
- 4
- Database :
- Complementary Index
- Journal :
- Geostandards & Geoanalytical Research
- Publication Type :
- Academic Journal
- Accession number :
- 133441207
- Full Text :
- https://doi.org/10.1111/ggr.12239