Potassium argon dating accuracy

For the J to be determined, a standard of known age must be irradiated with the samples of unknown age.Because this (primary) standard ultimately cannot be determined by Ar, it must be first determined by another isotopic dating method.However, because each of these parameters is difficult to determine independantly, a mineral standard, or monitor, of known age is irradiated with the samples of unknown age.The monitor flux can then be extrapolated to the samples, thereby determining their flux.The monitoring of the interfering reactions is performed through the use of laboratory salts and glasses.For example, to determine the amount of reactor produced Ar ratio of the glass is then measured in the mass spectrometer to determine the correction factor that must be applied to the rest of the samples in that irradiation.Mechanical crushing is also a technique capable of releasing argon from a single sample in multiple steps.

In order for an age to be calculated by the Ar technique, the J parameter must be known.However, the Argon, a noble gas, constitutes approximately 0.1-5% of the Earth's present day atmosphere.Because it is present within the atmosphere, every rock and mineral will have some quantity of Argon.Traditionally, this primary standard has been a hornblende from the Mc Clure Mountains, Colorado (a.k.a. Once an accurate and precise age is determined for the primary standard, other minerals can be dated relative to it by the Ar technique (e.g. However, while it is often easy to determine the age of the primary standard by the K/Ar method, it is difficult for different dating laboratories to agree on the final age.Likewise, because of heterogeneity problems with the MMhb-1 sample, the K/Ar ages are not always reproducible.

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