用于二次离子质谱法铀铅地质年代测定的两种锆石参考物质：GZ7和GZ8

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

作者信息

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

机构信息

Institut für Mineralogie und Kristallographie Universität Wien Althanstr. 14 Wien A-1090 Austria.

Department of Geosciences and CEED (Centre for Earth Evolution and Dynamics) University of Oslo P.O. Box 1047 Blindern Oslo 0316 Norway.

出版信息

Geostand Geoanal Res. 2018 Dec;42(4):431-457. doi: 10.1111/ggr.12239. Epub 2018 Oct 8.

DOI:10.1111/ggr.12239

PMID:30686958

原文链接:https://pmc.ncbi.nlm.nih.gov/articles/PMC6334521/

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 Pb/U 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 × 10 g (GZ7) and 2.53 × 10 g (GZ8), respectively, and the (U-Th)/He ages of 438 Ma ± 3 Ma (2) for GZ7 and 426 Ma ± 9 Ma (2) for GZ8 are typical of unheated zircon from Sri Lanka. The mean U mass fractions are 680 μg g (GZ7) and 1305 μg g (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 ± 0.18 μg g; 95% confidence uncertainty) may prove useful as reference material for Ti-in-zircon temperature estimates.

摘要

在此，我们记录了两颗锆石宝石GZ7和GZ8的详细特征。两颗宝石质量相同，均为19.2克拉（3.84克）；二者均来自斯里兰卡拉特纳普勒地区的砂矿。在衰变常数的不确定度范围内，两种情况下的铀铅数据均一致，得出加权平均铅铀年龄（95%置信不确定度）分别为530.26百万年±0.05百万年（GZ7）和543.92百万年±0.06百万年（GZ8）。GZ7和GZ8均未经过任何加热的宝石优化处理。与结构相关的参数分别与计算得出的α剂量1.48×10克（GZ7）和2.53×10克（GZ8）吻合良好，GZ7的（铀-钍）/氦年龄为438百万年±3百万年（2），GZ8的为426百万年±9百万年（2），这是斯里兰卡未加热锆石的典型特征。平均铀质量分数分别为680微克/克（GZ7）和1305微克/克（GZ8）。这两个锆石样品被提议作为二次离子质谱（SIMS）铀铅地质年代学的参考物质。此外，GZ7（钛质量分数为25.08微克/克±0.18微克/克；95%置信不确定度）可能作为锆石中钛温度估算的参考物质有用。