Potassium—argon methods with special reference to basic igneous rocks

Abstract

The theory, analytical method, and experimental errors of potassium–argon radiometric age-determination are briefly reviewed. The choice of suitable material for analysis and the application of the method to basic igneous and other rocks using whole-rock samples are described. ‘Discrepancy’ in potassium-argon age-determination is defined; geological factors that control the accuracy of potassium-argon ages, and must be taken into consideration in their interpretation, are discussed. It is asserted that, in favourable circumstances, potassium-argon age studies can provide a wide variety of alternative information of geological significance as well as, or instead of, indicating the initial age of consolidation of a rock: in particular, that it is possible to define the dates of subsequent cleavage, metasomatism, or metamorphism from a consideration of the discrepantly low ages obtained from older rocks.