How can laser heating be used to date a single mineral grain?

In the context of geochronology, laser heating is a powerful technique used to analyze minute amounts of gas or material from a single mineral grain, particularly within the potassium–argon dating method.

By focusing an intense laser beam onto a single spot on a crystal, researchers can release the trapped argon gas. For potassium-rich materials, this single spot often provides sufficient gas for analysis by a highly sensitive gas mass spectrometer. In the case of very young materials, the entire millimeter-sized grain may be melted by the laser to obtain an accurate measurement. This approach allows for the precise determination of ages and helps identify complexities such as inherited older grains within a sample.1

Additionally, laser systems are used in other analytical techniques, such as laser ablation–inductively coupled plasma–mass spectrometry (LA-ICP-MS). In this process, a laser beam creates a small pit on the surface of a mineral, and the resulting ions are analyzed by a mass spectrometer to determine their mass and energy. This method is particularly efficient for rapidly dating large numbers of single zircon grains.2