is a radiometric dating method invented to supersede potassium-argon (K-Ar) dating in accuracy.Ar dating is a major method that researchers have used to understand the structural evolution of the Maria Fold and Thrust Belt.

argon 39 argon 40 dating-50

The standards of known age are used to account for differences in the neutron flux during irradiation.

Argon-36 in the sample accounts for any air contamination.

This plateau must be used with caution, however, because it could have been lowered by later events and therefore may represent a minimum constraint on the age of crystallization.

Hypothetical profiles of argon concentrations through the grain, and associated step-heating results.

Potassium-40 is radioactive but has such a long half-life that it is primordial - it has been around since the earth was being formed. About 10.7% decays to Argon-40 by emitting a positron.

Because of this, we can assume that the potassium-40:potassium-39 ratio in minerals at any time is a constant. If the argon-40 stays trapped in the crystal and you can measure the ratio of potassium-40 to argon-40, then you know how long it has been since the mineral formed.

To understand argon-argon dating, you need to understand potassium-argon dating.

The isotope potassium-39 makes up about 93% of natural potassium.

Some of the potassium-39 forms argon-39 by an n,p reaction.