Exploring the age standard of (U-Th)/He thermochronology; Evaluation of eight zircon samples

Fukuda, Shoma   

The (U-Th)/He thermochronometer is a method used to estimate the age based on the alpha decay of U and Th series in mineral crystals with U and Th concentrations as the parent isotopes and He-4 content as the daughter isotope. This method is utilized for dating within 0.1 to 100 Myr timescales. Its low closure temperature allows for reconstruction of geoscientific phenomena such as uplift/erosion in mountains, fault movements, and volcanism and magmatism. Regarding zircon (U-Th)/He (hereinafter, ZHe) method, the Fish Canyon Tuff zircon (a standard of zircon fission-track method) has been employed empirically as a reference material. However, some of these zircons have yielded heterogeneous U-Th distributions. Therefore, new potential zircons for (U-Th)/He dating are desirable. In this study, we conducted ZHe dating on eight zircons from potential samples collected in Japan and other age standards, and evaluated the consistency, age dispersions and their factor. Consequently, the Utaosa rhyolite (TRG04) and Mt. Dromedary (a zircon fission-track age standard) have the potential as reference materials in the ZHe method. As future prospect, we plan to conduct a round-robin test for inter-laboratory comparison.