Potassium argon dating problems
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.
J value uncertainty can be minimized by constraining the geometry of the standard relative to the unknown, both vertically and horizontally.
The NMGRL does this by irradiating samples in machined aluminum disks where standards and unknowns alternate every other position.
In order for an age to be calculated by the Ar technique, the J parameter must be known.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.For example, laser spot sizes of 100 microns or less allow a user to extract multiple argon samples from across a small mica or feldspar grain.The results from a laser probe can be plotted in several graphical ways, including a map of a grain showing lateral argon distribution.