青藏高原隆升过程的磷灰石裂变径迹分析方法

The apatite fission track analysis applied to the exploration of the uplifting of the Qinghai-Xizang Plateau

关键词:  高原隆升  磷灰石裂变径迹  径迹年龄-海拔高程法  青藏高原

Key words:  plateau uplifting  apatite fission track  track ages-height deviation method  Qinghai-Xizang Plateau

摘要:

由于青藏高原新生代以来地表高程持续强烈抬升,在利用磷灰石FT年龄进行高原绝对隆升速率计算时应引入古地表高程参数,而通常使用的"径迹年龄-地形高差法"却没有考虑到不同时期的古地表高程问题。为此,笔者试提出高原隆升速率计算的"径迹年龄-海拔高程法",即以同一参考质点(样品点)在不同时期的海拔高程差作为绝对抬升量,以绝对抬升量除以时间得出隆升速率。本文讨论了改进后方法与传统方法计算结果的差异及合理性。鉴于青藏高原的隆升具有明显的脉动性与幕式作用特征,多数情况下FT年龄可能大致代表构造抬升与剥露事件的年代。

Abstract:

Due to the rapid and sustained uplifting of the Qinghai-Xizang Plateau from the Cenozoic onwards, the ancient Earth's surface elevation parameters should be introduced into the calculation of the uplifting rates of the Plateau. However, they are generally not taken into account by using the commonly used "track ages-topographic deviation" method. In these cases, the "track ages-height deviation" method is put forward here as a new technique for the calculation of the uplifting rates of the Plateau. The method is constructed by taking the elevation above sea level of one spot (sampling site) during different periods as an absolute uplifting amount, which is divided by time, and then an uplifting rate may be obtained. The different and reasonable aspects are discussed for the above-mentioned methods. In most cases, the fission track ages may represent those of tectonic uplifting and erosional events in terms of the pulses and episodes of the uplifting of the Plateau.