Simultaneous determination of alteration and eruption ages of volcanic rocks by electron spin resonance
The alteration and eruption ages of Japanese welded tuffs were estimated by the method of ESR using Ge, OHC and Al centers in quartz whose stabilities are different. The ages obtained from the Ge and OHC centers were 1-2 Ma, however the ages from the Al center varied from 0.059 to 1.36 Ma. The comparison of these ages with thermoluminescence (TL) and fission track (FT) ages proves that the ESR age of the Al center, which agrees with the TL age, shows the thermal history and, in an ideal case, gives the alteration age: those of the Ge and OHC centers, which agree with FT age, indicate the eruption age. Therefore, this method enables us to describe the thermal history of a rock.