Potassium argon dating accuracy
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 quantity of potassium in a rock or mineral is variable proportional to the amount of silica present.
Therefore, mafic rocks and minerals often contain less potassium than an equal amount of silicic rock or mineral.
Step-heating is the most common way and involves either a furnace or a laser to uniformily heat the sample to evolve argon.
The individual ages from each heating step are then graphically plotted on an age spectrum or an isochron.
In order for an age to be calculated by the Ar technique, the J parameter must be known.
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.
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.
However, the Argon, a noble gas, constitutes approximately 0.1-5% of the Earth's present day atmosphere.