K-Ar geochronology of fault

Tamura, Hajimu; Sato, Keiko*

K-Ar age of fault is sometimes exclusive fact age of fault activity though the age of fault activity is determined on stratigraphy and ages by different dating methods. This note describes application of K-Ar dating to fault sample. Pseudotachylyte and Authigenic illite in fault gauge are major target material of dating. Sample preparation and determination of age are difficult for both of them and the geochronology is still in development stage. Dating examples of Pseudotachylyte says that sample separation is important to select part which was equilibrate to atomosphere in generation by spot analysis like laser fusion Ar-Ar dating, as illite examples that sample preparation to obtain fine - about 1 micrometer or less - grain and sample determination by inspection with electron microscope or XRD analysis are important.