^<40>Ar-^<39>Ar法による年代測定 : 基礎とその問題点  [in Japanese] Age determinations by the ^<40>Ar-^<39>Ar method : Principles and related problems  [in Japanese]

The ^<40>Ar-^<39>Ar method has a lot of merits as a dating tool for rocks and minerals over the conventional K-Ar method, especially when it is accompanicd with the stepwise heating technique. In order to get reliable ages by this method, however, appropriate precautions are necessary including the conditions of neutron irradiations for samples and the kinds of used materials. In favourable cases, the ^<40>Ar-^<39>Ar method can recover the original age of a sample even if it was moderately disturbed by a later event. Generally terrestrial samples show more complex age patterns compared with those of meteorites and/or lunar rocks when they are disturbed. There still remain some fundamental problems to be solved in this method in order to interprete the ^<40>Ar-^<39>Ar age pattern of terrestrial samples properly.