Ar ar dating
If you're seeing this message, it means we're having trouble loading external resources on our website.If you're behind a web filter, please make sure that the domains *.and *.are unblocked.K has a half-life of 1.248 billion years, which makes it eminently suitable for dating rocks.Potassium is chemically incorporated into common minerals, notably hornblende, biotite and potassium feldspar, which are component minerals of igneous rocks.(However, see the section below on the limitations of the method.) This suggests an obvious method of dating igneous rocks.If we are right in thinking that there was no argon in the rock originally, then all the argon in it now must have been produced by the decay of Ar in them will be so small that it is below the ability of our instruments to measure, and a rock formed yesterday will look no different from a rock formed fifty thousand years ago.Potassium–Argon dating or K–Ar dating is a radiometric dating method used in geochronology and archaeology.It is based on measurement of the product of the radioactive decay of an isotope of potassium (K) into argon (Ar).
The infra-red laser (continuous wavelength 60W 1064 nm Nd-YAG) is capable of spot analysis (100-300 µm spot size), single grain total fusion, and incremental laser step-heating of K-rich minerals and whole rocks.When a rock undergoes metamorphism, some or all of its argon can be outgassed.If all the argon was lost, this would reset the K-Ar clock to zero, and dating the rock would give us the time of metamorphism; and if we recognized the rock as metamorphic this would actually be quite useful.The reasoning is as follows: the atmosphere does not only contain Ar as being atmospheric argon.However, this only works if all the excess argon did indeed come from the atmosphere.
Another concern with K-Ar dating is that it relies on there being no Ar in the rock when it was originally formed, or added to it between its formation and our application of the K-Ar method.