石英中の常磁性格子欠陥の熱安定性の研究によるESR年代測定の基礎の確立

抄録

The ESR (electron spin resonance) dating method has been applied to faults, tephras, sediments and flints, using quartz. This paper summarizes the studies on thermal stabilities of paramagnetic defects observed in natural quartz, E₁', Al and Ti centers. The age ranges to which ESR dating can be applied were estimated from the results of heating experiments. The decay kinetics of these three centers was found to be second order. A method to estimate the amount of oxygen vacancies in quartz was proposed, which involves measuring the intensity of the E₁' center after irradiation to more than 200 Gy and subsequent heating at 300℃ for 15 minutes. Using this technique, oxygen vacancies were found to be much more stable than other paramagnetic centers. A correlation was observed between the geologic ages of the granites and of tephras and the amount of oxygen vacancies in quartz. The external β and γ rays can create the oxygen vacancies as indicated by the experiment of irradiation by ⁶⁰Co source.