Evaluation of eight zircon samples as potential reference material for (U-Th)/He thermochronometry

Fukuda, Shoma   ; Barry, K.*; Sueoka, Shigeru   ; Danhara, Toru*; Iwano, Hideki*; Tagami, Takahiro*

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.