The idea is to subject the sample to neutron irradiation and convert a small fraction of the 39K to synthetic 39Ar, which has a half life of years. Sedimentary rocks: K-Ar dating of authigenic mineral phases has often been attempted but remains difficult. Dating detrital minerals such as white mica muscovite, phengite in fluvial sediments is frequently used to study the metamorphic history of the hinterland.
Potassium–argon dating, abbreviated K–Ar dating, is a radiometric dating method used in Ar accumulated to the amount of K remaining. The long half-life of K allows the method to be used to calculate the absolute age of samples. The positron emission mechanism mentioned in Chapter has an extremely long half life and can therefore safely be neglected. In addition to 40Ar, argon has.