FT thermochronology is widely used for reconstruction of low-temperature thermal histories in upper crustal rocks.The method has found particular application in estimating temperature history and long-term denudation rates in orogenic belts, rifted margins and more stable areas, providing a means of assessing the timing and volume of sediment being delivered to sedimentary basins, and as an estimator of hydrocarbon maturity potential.As one answer to his critics, Kelvin produced a completely independent estimate -- this time for the age of the Sun.His result was in close agreement with his estimate of the age of the earth.
Spontaneous fission is the process whereby a heavy and unstable atom disintegrates into two particles of roughly equal size, which move in opposite directions through the crystal lattice of the host mineral, creating a damage trail of 10-15μm length (Figure 1).
The submicroscopic tracks accumulate over time and are revealed by chemical etching of polished internal surfaces of the crystal (Price and Walker, 1962).
For the fission-track system of apatite a transition zone where tracks are essentially unstable is recognized.
With time, the density (tracks per unit area) of these so-called 'fission tracks' increases at a rate that is proportional to the U-concentration of the mineral.
Although fission tracks are are too small to see with even the most sensitive microscopes, they can easily be revealed by acid etching.