Selected minerals are irradiated offsite to produce 39Ar from 39K (as a proxy for radioactive 40K).Samples are co-irradiated with monitor standards to define the "J-value", used for age calculations.
The versatility of the Ar method permits determining the timing of processes and events such as igneous intrusions and extrusions, ore mineralization and hydrothermal fluid circulation, metamorphic cooling and exhumation, mineral formation and recrystallization, and shallow crustal faulting.
The primary instrument in the lab is a Micromass VG 5400 mass spectrometer attached to a CO2 laser extraction system.
The system is fully automated and controlled by the Mass Spec software developed by Al Deino at the Berkeley Geochronology Center.
The sample preparation facilities include a series of microscopes to allow the inspection of mineral separates, sample picking, and loading of the irradiation packets.
A separate and secure microscope room is used for the unloading of irradiated samples and radioactive storage.