Fission track annealing and age determination of chlorite

Systematic annealing experiments have been carried out in order to obtain correction factors for the ages of chlorite, which may have undergone geological annealing. All the tracks in the mineral are annealed by heating for one hour at 500°. Extrapolation of experimental data suggests that a temperature of 160° would be required for 10⁶ years to remove all the tracks in chlorite. Ages of 6 samples have been determined. The corrected age of 606 ± 17 × 10⁶ y obtained for Nellore, Andhra Pradesh, India, agrees well with the ages of coexisting minerals, determined by the fission-track method. The activation energy for chlorite ranges from 1.2 to 2.0eV, with a mean value of 1.5 eV.