How accurate is potassium argon dating dating a psychopath signs
That is, a fresh mineral grain has its K-Ar "clock" set at zero.
The method relies on satisfying some important assumptions: Given careful work in the field and in the lab, these assumptions can be met.
A variant of the K-Ar method gives better data by making the overall measurement process simpler.
The key is to put the mineral sample in a neutron beam, which converts potassium-39 into argon-39.
The site also must be geologically meaningful, clearly related to fossil-bearing rocks or other features that need a good date to join the big story.
Lava flows that lie above and below rock beds with ancient human fossils are a good—and true—example.
The potassium-argon (K-Ar) isotopic dating method is especially useful for determining the age of lavas.
What simplifies things is that potassium is a reactive metal and argon is an inert gas: Potassium is always tightly locked up in minerals whereas argon is not part of any minerals. So assuming that no air gets into a mineral grain when it first forms, it has zero argon content.Finally, the argon atoms are counted in a mass spectrometer, a machine with its own complexities.Three argon isotopes are measured: Ar is determined by comparison to it.Variations in this data may point to errors anywhere in the process, which is why all the steps of preparation are recorded in detail.K-Ar analyses cost several hundred dollars per sample and take a week or two.
A precise amount of argon-38 is added to the gas as a "spike" to help calibrate the measurement, and the gas sample is collected onto activated charcoal cooled by liquid nitrogen.