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.
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.
This flux is known as the 'J' and can be determined by the following equation: As the table above illustrates, several "undesirable" reactions occur on isotopes present within every geologic sample.
These reactor produced isotopes of argon must be corrected for in order to determine an accurate age.
Argon can mobilized into or out of a rock or mineral through alteration Ar and potassium, there is not a reliable way to determine if the assumptions are valid.
The NMGRL does this by irradiating samples in machined aluminum disks where standards and unknowns alternate every other position.
The isotopes the KAr system relies on are Potassium (K) and Argon (Ar).
Potassium, an alkali metal, the Earth's eighth most abundant element is common in many rocks and rock-forming minerals.
Potassium can be mobilized into or out of a rock or mineral through alteration processes.
Due to the relatively heavy atomic weight of potassium, insignificant fractionation of the different potassium isotopes occurs.