鲜水河-小江断裂带作为川滇地块的东侧边界，是一条重要的陆内左行走滑断裂带，其各段的启动时间是研究青藏高原东南缘新生代走滑扩展及挤出过程的重要边界条件。目前对其起始活动时间还存在一些争议，尤以其南段的小江断裂的研究程度最弱，存在着“中新世晚期启动”和“上新世以后启动”两种主要观点。分析发现，位于小江断裂西侧的汤丹冲断块的隆升与小江断裂的走滑活动之间有着密切的联系，可通过研究前者的隆升剥露过程来约束后者的走滑启动时间。本项目拟将汤丹冲断块作为主要研究对象，通过采集冲断块内的基岩样品，利用磷灰石(U-Th)/He和裂变径迹定年的方法，对其新生代隆升剥露过程开展低温热年代学的研究，以此来限定小江断裂的启动时间，并结合前人在甘孜-玉树断裂和鲜水河断裂取得的研究成果，进一步确定鲜水河-小江断裂可能的演化序列，本项目的研究成果对揭示鲜水河-小江断裂新生代的发育时序具有重要的意义。

Xianshuihe-xiaojiang fault (XXF), as an east boundary of Chuandian block, is an important intracontinental left-lateral strike-slip fault, and the initiation of the XXF is a key factor to research the development of strike-slip fault in east Tibet. The Xiaojiang fault (XjF), as a south part of the XXF, has great impact on the development squence of the XXF. There are two major models for the initiation of this fault which are the XjF began at Miocene and began at Pliocene. Low-temperature thermochronometry, which can record rock exhumation history, is informative to differentiate between models. This project intends to collect bedrocks from Tangdan thrust block which locates in the west of the XjF. By dating these rocks with apatite (U-Th)/He and apatite fission-track methods, the regional exhumation pattern and initiation will be constructed. Finally, a geological model will be built to investigate the XXF development sequence in the Cenozoic.