Abstract
Fission track annealing experiments under optimized sets of etching conditions have been carried out on biotite mineral from a pegmatitic intrusive body of Pokharia mica mine in Hazaribagh district of Bihar (India). The mean values of range for induced 235U fission fragments, uranium content and activation energy determined are 19.3±1.6μ m, 0.2ppm, and 1.5eV respectively. The graphs depicting the variation of optimum etch time, activation energy, and track length shrinkage with annealing in track density have been drawn for their use in fission track dating. Annealing characteristics of micaceous minerals like biotite, chlorite, vermiculite, phlogopite and muscovite show that the track clock in them got reset at 100, 110, 125, 150 and 170°C respectively between the annealing eras 105 to 107 years. The analysis of track annealing in biotite and its comparison with other micaceous as well as nonmicaceous minerals suggest that biotite is lowest geological thermometer among the minerals studied so far in fission track geochronology.
