Report of the (U-Th)/He dating system at Tono Geoscientific Research Unit, Japan Atomic Energy Agency

Yamada, Kunimi; Hanamuro, Takahiro  ; Tagami, Takahiro*; Yamada, Ryuji*; Umeda, Koji

Japan Atomic Energy Agency have jointly set up the lab of the (U-Th)/He dating in cooperation with Kyoto University. At the present stage, samples are apatite and zircon. Infrared laser heating in vacuum chamber extracts helium. The helium is quantified using the MM5400 rare gas mass spectrometer and the sensitivity method. The sensitivity of the mass spectrometer is calibrated using standard air, a volume-known pipette, and a capacitance manometer. The ICP quadrupole mass spectrometer quantifies uranium and thorium using standard addition method after dissolution of the gas-extracted sample. Apatite is dissolved using HNO and zircon is decomposed by the alkali-fusion method using XRF bead sampler and LiBO. We are performing the calibration of MM5400 and testing dissolution procedures for ICP at present, and will report detailed views of dating systems in addition to them.