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.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.Instead, the ratios of the different argon isotopes are measured, yielding more precise and accurate results.Additional advantages of the single isotopic measurements of the K.
Laser probes also allow multiple ages to be determined on a single sample aliquot, but do so using accurate and precise spatial control.
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.