Evaluation of zircon from the Pliocene Utaosa rhyolite Japan as reference material for (U-Th)/He thermochronometry

Fukuda, Shoma   ; Kohn, B.*; Sueoka, Shigeru   ; Kagami, Saya   ; Kajita, Yuya*; Minami, Saki*; Okamoto, Akira*; Tagami, Takahiro*

The zircon (U-Th)/He (ZHe) system with a typical closure temperature of ~160-200 degree Celsius (Reiners et al., 2004), but lower for higher radiation damaged grains (Guenthner et al., 2013), offers the potential for evaluating thermal histories in the uppermost ~10 km of the crust. ZHe thermochronometry has been applied to different geological settings in order to estimate tectonics, uplift and denudation, basin evolution, etc. (Ault et al., 2019), which can also contribute to evaluating long-term tectonic stabilities for the geologic disposal project. We have attempted to assess suitable zircon samples as ZHe age standards by using rapid cooling rock samples of relatively young (100 Ma) age. This is because such rock samples are expected to empirically exhibit simple thermal histories and little radiation damage. Therefore, age dispersion caused by radiation damage can be relatively small. In order to reassess previous data obtained by Tagami et al. (2003), ZHe analyses of the Pliocene Utaosa rhyolite (TRG-04 and -07) and the Miocene Buluk Tuff have been carried out. In addition, OD-3 zircon (Iwano et al., 2013), a zircon U-Pb age standard, was also analyzed. In this presentation, preliminary ZHe age data from these samples will be presented and compared to evaluate their suitability as ZHe reference materials.