ADVANCE OF FISSION-TRACK ANALYSIS METHOD AND ITS APPLICATION
裂变径迹定年方法的进展及应用

The unique thermal sensitivity of the apatite is potentially an important monitor of a crystal's thermal history throughout a range of temperatures that is critical to numerous processes in the upper crust~1,7]. At first this paper introduces the zeta calibration method~9-11] for fission-traCk dating. Second, the paper shows the progresses of studies of the influence on fission-track annealing of apatite composition and edsotropy~1]. There are two strategies on measuring fission track length, confined and projected track length measurement. Many studies show that confined tracks length distribution approximates the real length distribution. In practice, the horizontal confined tracks measurement is recommend~13-15]. Based on the confined track length measurement, its distributions can be obviously divided 5 groups, such as induced track length distribution, undisturbed volcanic distribution, undisturbed-basement distribution, mixed distribution and bimodal distribution~13,14]. The length distribution of projected tracks can also be successfully applied to thermal analysis despite the fact that it is heavily biased against the real length distribution~12]. A partial track annealing concept based on the projected length distribution is introduced, in which the fission-track apparent age can be calculated from the sub-population of apatite projected length's 1_x. The age-spectrum~17] of apatite can reveal information of the thermal history of natural samples. Recently, an empirical equation has been developed to quantitatively describ the annealing process, i.e. decrease in mean track length with increasing temperature and heating time and to estimate the annealing degree in natural samples. Finally, two important applications of the fission-track method for studying thermal histories of the basin and orogenic belt are presented.