The Ar-Ar dating technique was developed by Merrihue and Turner (1966) and proved to be an extremely powerful geochronological tool even before the advent of laser extraction techniques. The strength of Ar-Ar dating lay in the stepped heating procedure (Turner, Miller and Grasty, 1966), applied with great success to extraterrestrial samples. Most studies of lunar rocks and soils have been conducted on samples collected by the Apollo and Luna missions, but these represent samples from near-equatorial regions of the near side of the Moon.However, recent discoveries of lunar meteorites, which have been blasted off the Moon only to land in the hot desserts and Antarctic ice fields of Earth, have provided great impetus to lunar science.The dating uses the radioactive processes in monazite as a clock.The uniqueness of monazite geochronology comes from the high thermal resistance of monazite, which allows age information to be retained during the geological history.
The probe data overall are consistent with the isotopic age, but with considerable variability (see the data spreadsheet, and the grain maps and images for details).
JB54: Tusas Mountains, Cerro Colorado near Ojo Caliente, NM.
This sample is currently used at UMass to test analytical precision.
Because of the age zonation, dating should be done on individual zones, rather than the whole crystal.
Also, textures of monazite crystals may represent certain type of events.