What is k ar dating used for
What is k ar dating used for - blog dating romance
The potassium-argon (K-Ar) isotopic dating method is especially useful for determining the age of lavas.Developed in the 1950s, it was important in developing the theory of plate tectonics and in calibrating the geologic time scale.
Any alteration or fracturing means that the potassium or the argon or both have been disturbed.
The rock samples are crushed, in clean equipment, to a size that preserves whole grains of the mineral to be dated, then sieved to help concentrate these grains of the target mineral.
The selected size fraction is cleaned in ultrasound and acid baths, then gently oven-dried.
Potassium occurs in two stable isotopes (Ar atoms trapped inside minerals.
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.
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.
However, we cannot rely on all the argon being lost, and if it is not then when we apply K-Ar dating this will give us an essentially arbitrary date somewhere between the formation of the rock and the metamorphosis event.
For these reasons K-Ar dating has largely been superseded by Ar-Ar dating, which will be the subject of the next article.
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.
Because argon is inert, it cannot be chemically incorporated in the minerals when they are formed, but it can be physically trapped in the rocks either during or after formation. If the source of this argon is atmospheric contamination, then we can correct for this.
But consider what happens if the argon came from deep within the Earth, where it was formed by Ar ratio as is found in the atmosphere, and the formula that corrects for atmospheric carbon will not correct for this.