The ⁴⁰Ar/³⁹Ar geochronological method is based upon the potassium argon isotopic system and involves the measurement of potassium ions by irradiation with fast neutrons in a nuclear reactor. The method can be applied to an age range of <20,000 years to 3 billion years. The primary applications are low- to mid-temperature tectonic events, metamorphic history uplift and cooling history, ore genesis, neotectonics, age of volcanism or plutonism.