Define isotopic dating
any method of determining the age of earth materials or objects of organic origin based on measurement of either short-lived radioactive elements or the amount of a long-lived radioactive element plus its decay product.
A method for determining the age of an object based on the concentration of a particular radioactive isotope contained within it.
Thus, discretion and interpretation of age dating is essential.
Ar after cooling past the closing temperature and that this was properly sampled during analysis.
Similarly, the Permian-Triassic extinction is now dated at 252.5 Ma, which is effectively coincident with the age determined by other means for Siberian Traps basalt flows.
The amount of the isotope in the object is compared to the amount of the isotope's decay products.
Dating of movement on fault systems is also possible with the Ar method.
Different minerals have different closure temperatures; biotite is ~300°C, muscovite is about 400°C and hornblende has a closure temperature of ~550°C.
However, in a metamorphic rock that has not exceeded its closure temperature the age likely dates the crystallization of the mineral.
One problem with argon-argon dating has been a slight discrepancy with other methods of dating.) reports that a correction of 0.65% is needed.