Experimental study on hydrothermal annealing of fission tracks in zircon

Increasing temperature causes fading of fission tracks (FTs) in minerals, which has been quantified by many laboratory heating experiments in atmosphere. In order to elucidate whether or not FT annealing at hydrothermally pressured conditions is the same as that at atmospheric condition, we performed zircon heating experiments using a hydrothermal synthetic apparatus. For reliable comparison, we annealed the same zircon samples using the same temperature monitor and analyzed them using the same experimental procedure as the previous experiment at atmosphere [Yamada et al., Chem. Geol. (Isot. Geosci. Sect.) 122 (1995) 249]. The observed FT annealing characteristics are indistinguishable between atmospheric and hydrothermally heating. It is therefore implied that the annealing kinetics of FT in zircon previously established can be applied to thermal history analysis of rocks that were subjected to hydrothermal conditions in nature, such as those in fault and subduction zones.