Ar ar dating
The strength of Ar-Ar dating lay in the stepped heating procedure (Turner, Miller and Grasty, 1966), applied with great success to extraterrestrial samples.
The technique involves sequentially increasing the temperature (stepped heating) of a vacuum furnace into which the sample has been loaded.
However, Ar dating of clay minerals remains challenging as technical factors, such as the non-standardized encapsulation, may have potential unexpected effects.
Both dating methods have their limitations: (1) K–Ar dating requires relatively large samples (ca.
is known to cause grave problems in regional geochronology studies.
For example, in the Middle Proterozoic Musgrave Block (northern South Australia), a wide scatter of K-Ar mineral "ages" was found, ranging from 343Ma to 4493Ma due to inherited (excess) , permitting inclusion of the gas in the crystallizing minerals.
Likewise, when Ar "dating" was attempted on Proterozoic granulite-facies rocks in the Fraser Range (western Australia) and Strangways Range (central Australia), it was found that garnet, sapphirine, and quartz contained excess was probably incorporated at the time of the formation of the minerals, and calculations suggested a partial pressure of ~0.1 atm Ar in the Proterozoic lower crust of Australia, which extends over half the continent.