PRELIMINARY DISCUSSION ON THE IMPACT OF PRESSURE ON FISSION TRACK ANNEALING OF APATITE

Fission track analysis of apatite is an effective method to determine low temperature thermal history of rocks. The track length after annealing is affected by many factors such as temperature, pressure, chemical composition of apatite, the included angle between track and crystallographic C axis, etched diameter (D_par) and age, but there are few articles about the effect of pressure. Based on a large number of domestic and oversea literatures, the authors illustrate the effect of pressure on track annealing by plotting the statistical data. The results show that pressure has significant effects on track annealing:The greater the pressure is, the shorter the track length after annealing is. With the pressure increasing, the degree of shortened track also increases. When the pressure is less than 150 MPa, the influence of pressure may be negligible, and the track annealing is mainly affected by temperature. Pressure and temperature complement each other in the fission track annealing of apatite, namely, high pressure with low temperature, or low pressure with high temperature, can all achieve the same degree of annealing.