Dating Single Zircon by Fission-Track and U-Pb Methods-A Case Study on a Granite at the Cooper Basin HFR Site, Australia-

Abstract

Both fission-track (FT) and U-Pb dating methods have contributed to determining the timing of volcanic activity and the thermal history of granitic plutons. Zircon FT dating provides information at a temperature of ~250-300 ºC and zircon U-Pb determines the timing of zircon crystallization. If both dating techniques are applied to the same zircon crystal, a more clear understanding is possible for the thermal history of the dated zircon crystal and its host rock, while to date few attempts have been done in this regard.
Here, these two dating methods were applied to a granitic host rock at the Cooper Basin Hot Fractured Rock (HFR) site, Australia. Firstly, a zircon FT age of ~170 Ma was obtained. Together with zircon FT length data, it was assumed that the granite has experienced much higher temperature (280-320ºC) than the present one (220-250ºC) during a later stage of its subsidence history. Secondly, analyzing the same zircons used for FT dating, a reliable LA-ICP-MS U-Pb age of ~330 Ma was obtained. Therefore it was revealed that both FT and U-Pb dating are applicable using the same zircon grains.