A test for excess radiogenic argon in micas

Radiogenic argon in excess of that produced by the in situ decay of potassium was first reported by Aldrich and Nier [1948] for the mineral beryl. Damon and Kulp [1958] reported a similar phenomenon for tourmaline and cordierite, as well as for beryl. Since then, excess argon has also been found in pyroxene [Hart and Dodd, 1962; McDougall and Green, 1964; Lovering and Richards, 1964] and in quartz and fluorite [Lippolt and Gentner, 1963; Rama et al., 1965]. The presence of excess argon has never been proved in the potassium micas which are so commonly used for K-Ar age determination.