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Potassium 40 argon 40 dating


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. However, if the mineral contains any potassium, then decay of the 40 K isotope present will create fresh argon-40, that will remain locked up in the mineral. Since the rate at which this conversion occurs is known, it is possible to determine the elapsed time since the mineral formed by measuring the ratio of 40 K and 40 Ar atoms contained in it.

Potassium naturally occurs in 3 isotopes: 39 K (%), 40 K (%), 41 K (%). Two are stable, while the radioactive isotope 40 K decays with a half-life of 7016393838848000000♠ × 10 9  years to 40 Ca and 40 Ar . Conversion to stable 40 Ca occurs via electron emission ( beta decay ) in % of decay events. Conversion to stable 40 Ar occurs via electron capture in the remaining % of decay events. [3]


Potassium 40 argon 40 dating

Potassium 40 argon 40 dating





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