Fission track dating method
By counting the spontaneous and induced tracks over exactly the same area, the age calculation reduces to a simple comparison of two Poisson-distributed variables ().
The EDM emerged as the dominant method because it offers significant advantages over the other approaches.The development of LA-ICP-MS has allowed fission track geochronologists to routinely determine the U per unit volume.Please note that uranium sitting near the counting surface of the grain will contribute more to the spontaneous track budget than more deeply seated uranium.It is clear that some fission-track ages can simply be experimental artifacts of the methods used.The population and external detector methods remain the best alternatives in most mineral dating situations; but very important restrictions are imposed by the effects of anisotropic etching and accumulated radiation damage.Using these measurements, the apparent fission track age ( ) is given by where is obtained by applying Equation 4 to an age standard and rearranging.
Equation 4 represents a classic case of a ‘matched pairs’ experimental design (Galbraith, 2010).
In a series of seminal papers published during the 1960s, Robert Fleischer, Paul B.
Price and Robert Walker showed how these fission tracks can be revealed to the human eye (aided by an optical microscope) by acid etching, forming the basis of a unique geochronometer (Price and Walker, 1962, 1963; Fleischer et al., 1964, 1965, 1975).
As a result, it is fair to say that the fission track method represents the gold standard among geochronometers in terms of statistical rigour.
Unfortunately, the EDM also has a number of practical shortcomings: U.
An ideal fission-track dating method is defined as one where spontaneous and induced tracks with identical properties are measured under identical registration, etching and counting conditions.