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Another routine approach that minimizes possible error due to disequilibrium is lab is gamma ray spectrometry, due to an inherited collection of Na I crystals from radioactive chemistry labs.
U at the time of sample formation must be known or calculated.
alpha dating by some authors) stretches farther back than any other radioisotopic dating technique (Rutherford, 1905).
It can arguably be interpreted as an allegory for the history of thermochronology in general, in which early, presumably nonsensical or inconsistent ages are later interpreted as geologically meaningful cooling ages in the context of additional kinetic and geologic constraints (e.g., see review in Reiners et al., 2005).
A correction has to be applied for the loss of radiogenic He generated within an outer rim of the mineral grain by the α-stopping distances (apatite: 25m).
The most important requirements for (U-Th-Sm)/He thermochronology are 1.) minerals free from inclusion and cracks, 2.) idiomorphic crystals, 3.) a homogeneous distribution of U and Th.
Differential solubility between uranium and its long lived daughter isotope Th is measured using MC-ICPMS.