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Kanno, Mizuho; Sueoka, Shigeru; Fukuda, Shoma
JAEA-Testing 2020-010, 38 Pages, 2021/03
JAEA-Testing-2020-010.pdf:3.07MB
This report provides procedures of He measurement for (U-Th)/He dating at Tono Geoscience Center, Japan Atomic Energy Agency. (U-Th)/He method is a radiometric dating based on alpha decay of U and Th series isotopes, being utilized as a thermochronometer. (U-Th)/He thermochronometries on zircon and apatite are especially useful to estimate thermal history at low temperatures. The procedures are presented with the details, tips, and cautions because parts of the procedures can be carried out by beginners, including students and contractors. This report also includes some document formats helpful for conducting the procedures.
Fukuda, Shoma; Barry, K.*; Sueoka, Shigeru; Danhara, Toru*; Iwano, Hideki*; Tagami, Takahiro*
no journal, ,
The zircon (U-Th)/He (ZHe) system often allows the reconstruction of thermal histories in the uppermost 10 km of crust based on a closure temperature of 160-200 degrees of Celcius under cooling rates of 1-100 degrees of Ceocius per Myr and moderate radiation damage. The Fish Canyon Tuff zircon, which has been used as reference material in several ZHe studies, may display strong U-Th zoning. This issue has led to recent studies for evaluating other possible zircons as reference materials for ZHe dating. Here, we report the results of our investigation of prospective ZHe thermochronology reference material for eight samples below 100 Ma and with relatively low radiation damage, selected from ZFT or U-Pb age standards and potential minerals in Japan. ZHe dating was performed on 30 zircon grains from each sample in order to evaluate their suitability. Only samples, TRG04-21 and Mt. Dromedary yielded concordant ZHe dates with respect to previously reported ages, while others yielded concordant and/or significantly younger ages with moderate to high dispersion.