The E1’ center in natural quartz: Its formation and applications to dating and provenance researches

Quartz is one of the minerals useful for electron spin resonance (ESR) dating. The E1′ center is one of well-known paramagnetic defects in crystalline quartz. This center has a unique feature; its intensity increases on heating. An electronic process to explain this increase was found to be controlled not only by the number of oxygen vacancies, which are the precursors, but also by the number of Al hole centers, which depend on the previous radiation dose and on the Al concentration.

The maximum intensity on heating is called the heat treated E1′ center, which has been posited to correspond to the number of oxygen vacancies in quartz and was found to be correlated with the ages of the host granites (Toyoda and Hattori, 2000). The experimental results on spin-spin relaxation times of the E1′ center indicate that external beta and gamma rays create oxygen vacancies in natural quartz rather than alpha or alpha recoil particles (Toyoda et al., 2005).

The correlation between the numbers of the oxygen vacancies in quartz and the ages of the host granite made it possible to distinguish the quartz of a sedimentary reservoir from another with different age of crystallization (Toyoda and Naruse, 2002). Quartz fractions extracted from leoss and atmospheric deposition in Japan and from sediments in Japan sea were analyzed by ESR. The temporal change of the contributions from two dust sources in China were discussed in the context of climate change.