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data on whole-rock material, though the methods are applicable to all published plateau data.
Ar is constant: 5) The sample must have remained a closed system since the event being dated (Mc Dougall and Harrison, 1999).
The ideal model conditions may not be met due to the presence of inherited argon, loss of radiogenic argon and deformation and recrystallization of the mineral (Dodson, 1973).
The argon released in each step is measured to calculate a “step age” with an associated analytical error.
or does it have the same magnetic susceptibility as muscovite?
The closure temperature range of a mineral is the temperature range over which a mineral changes from an open system to a closed system for the isotopes of interest.
The most important process interfering with the accumulation of radiogenic isotopes is recrystallization, as this enhances the mobility of atoms.
Argon, on the other hand, is an inert gas; it cannot combine chemically with anything.
As a result under most circumstances we don't expect to find much argon in igneous rocks just after they've formed.
K has a half-life of 1.248 billion years, which makes it eminently suitable for dating rocks.