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Potassium–argon dating, abbreviated K–Ar dating, is a radiometric dating method used in geochronology and archaeology. It is based on measurement of the product of the radioactive decay of an isotope of potassium (K) into argon (Ar). Potassium is a common element found in many materials, such as feldspars, micas, clay minerals, tephra, and ...
Together with stratigraphic principles, radiometric dating methods are used in geochronology to establish the geologic time scale. [3] Among the best-known techniques are radiocarbon dating, potassium–argon dating and uranium–lead dating.
Argon–argon (or 40 Ar/ 39 Ar) dating is a radiometric dating method invented to supersede potassium–argon (K/Ar) dating in accuracy. The older method required splitting samples into two for separate potassium and argon measurements, while the newer method requires only one rock fragment or mineral grain and uses a single measurement of argon isotopes.
Other radiometric dating techniques are available for earlier periods. One of the most widely used is potassium–argon dating (K–Ar dating). Potassium-40 is a radioactive isotope of potassium that decays into argon-40. The half-life of potassium-40 is 1.3 billion years, far longer than that of carbon-14, allowing much older samples to be dated.
Ar is used in potassium-argon dating of rocks. Minerals are dated by measurement of the concentration of potassium and the amount of radiogenic 40 Ar that has accumulated. Typically, the method assumes that the rocks contained no argon at the time of formation and all subsequent radiogenic argon (i.e., 40 Ar) was retained. [citation needed] 40
Potassium–argon dating and argon–argon dating. These techniques date metamorphic, igneous and volcanic rocks. They are also used to date volcanic ash layers within or overlying paleoanthropologic sites. The younger limit of the argon–argon method is a few thousand years. Electron spin resonance (ESR) dating
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Potassium-40 is especially important in potassium–argon (K–Ar) dating. Argon is a gas that does not ordinarily combine with other elements. So, when a mineral forms – whether from molten rock , or from substances dissolved in water – it will be initially argon-free, even if there is some argon in the liquid.