Fission-track dating of Quaternary volcanic glass by stepwise etching

The fission-track method has been applied to date volcanic glass from Quaternary tephra. The size of the spontaneous tracks in the volcanic glass is reduced at ambient temperatures, so the calculated age is often less than the expected eruption age. The underestimation of fission-track ages has been corrected using several methods, some of which have disadvantages in terms of time-consuming experiments and the use of radioactive materials. We examined a new protocol for the fission-track dating of glass that involves estimation of the track number per unit volume in a stepwise etching experiment and measurement of the 238U concentration by laser ablation inductively coupled plasma mass spectrometry. The bulk etching rate (Veg) is estimated in track geometry analyses using an assumed track etching model. As a result, reliable values for Veg and the track density are obtained, suggesting that this new dating protocol has the potential to provide reliable fission-track ages without nuclear irradiation and complicated age correction procedures.