Standardless fission-track ages of the IUGS age standards

Abstract

Standardless fission-track ages for four zircon, two titanite and three apatite age standards, most of them recommended by the Fission Track Working Group of the IUGS Subcommission on Geochronology, were redetermined. The age calculations used the decay constant for spontaneous fission of 238U (λf = (8.5 ± 0.1) 10−17 a−1) recommended by the IUPAC, the ratio of etchable to latent track length in both the dated minerals (zircon, titanite and apatite) and mica detectors and the 187 track counts with the external-detector and population methods. We found the resulting standardless fission-track ages are in line with results from more recent high precision geochronology including zircon U-Pb dating. These results confirm that standardless fission-track dating of zircon, titanite and apatite with the external-detector method is feasible, as well as dating of apatite with the population method, and that ζ-calibration can be based on the zircon U-Pb ages of the current standard samples. On the other hand, there is no room for an age correction for partial annealing of the fossil tracks based on their mean confined-track lengths of the apatite, titanite and zircon age standards.