裂变径迹定年方法的进展及应用

裂变径迹分析方法利用裂变径迹年龄及裂变径迹长度分布形态来反映随时间产生的裂变径迹积累及由温度控制的退火(裂变径迹缩短或消失)两种因素综合作用的结果。近几年来，有关磷灰石的退火特征进行了大量实验和野外研究，取得了较大进展。本文通过对80年代以来国内外裂变径迹研究状况的追踪调研结果，简要介绍裂变径迹定年方法的主要进展及应用情况。

ADVANCE OF FISSION-TRACK ANALYSIS METHOD AND ITS APPLICATION

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.