argon-40-argon-39 dating

Argon-40/Argon-39 dating is a geochronological technique used to determine the age of rocks and minerals. It is based on the radioactive decay of potassium-40 into argon-40.12

This method involves irradiating a sample in a nuclear reactor, which converts some potassium atoms into argon-39. Both argon-40 (the daughter product) and argon-39 (a proxy for the parent potassium) can then be measured in a mass spectrometer. This allows for the determination of both parent and daughter isotopes within the same sample, eliminating the need to measure potassium content separately and enabling the analysis of smaller sample sizes.2

A key advantage of the argon-40/argon-39 method is that the sample can be heated in stages, allowing scientists to analyze the age of different parts of the sample. This helps to identify and discard ages affected by alteration or reheating events, providing a more accurate age for the rock. This technique has been used to date materials ranging from meteorites billions of years old to volcanic rocks as young as tens of thousands of years.21