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.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.Argon loss and excess argon are two common problems that may cause erroneous ages to be determined.
Potassium, an alkali metal, the Earth's eighth most abundant element is common in many rocks and rock-forming minerals.
Ar total fusion measures ratios, making it ideal for samples known to be very argon retentive (eg. Total fusion is performed using a laser and results are commonly plotted on probability distribution diagrams or ideograms.
In order for an age to be calculated by the Ar technique, the J parameter must be known.
This imprecision (and inaccuracy) is transferred to the secondary minerals used daily by the Ar age equation will become continually more refined allowing much more accurate and precise ages to be determined.
Because the J value is extrapolated from a standard to an unknown, the accuracy and precision on that J value is critical.