新疆阿尔泰造山带构造活动的磷灰石裂变径迹证据

Fission track evidences for tectonic activity in Altay Mountains, Xinjiang, North-Western China

从对新疆阿尔泰造山带西部构造活动的研究中获得一批较为系统的磷灰石裂变径迹分析结果。 32个磷灰石裂变径迹年龄为 (16 3.0± 6 .4 )～ (4 6 .9± 7.2 )Ma ,平均径迹长度为 (14 .5± 0 .1)～(11.3± 0 .4 ) μm ,长度标准差为 1.4～ 2 .7μm。区内具有 3阶段热历史 :约 110Ma之前处于约 10 0～12 0℃较高温稳定阶段 ,然后在约 110～ 4 0Ma期间发生快速冷却与隆升事件 ,从约 4 0Ma开始发生另一较为缓慢的冷却事件。总体上自北而南 ,剥蚀速率和冷却速率均逐渐变小。文中裂变径迹资料表明 ,阿尔泰山西段主要断裂带现在向南倾斜 ,区内构造演化亦主要受Tesbahan、Kulti和Basei三条断裂带逆冲热事件的控制。

A series of apatite fission track analysis results have been achieved from Altay Mountains, Xinjiang. Total 32 fission track ages range from (163.0±6.4) Ma to (46.9±7.2) Ma and their confined lengths from (14.5±0.1) μm to (11.3±0.4) μm with standard deviations of ～1.4～2.7 μm. It is shown that there were three stages of the thermal history, i.e., higher temperature steadier stage of ～100～120 ℃ before ～110 Ma, rapid cooling and uplifting event during about 110～40 Ma, and slow cooling stage after ～40 Ma. The cooling rate and denudation rate decreased overall from north to south. It is found that the FT ages increase from Tesbahan fault, Kulti fault and Basei fault to the south, respectively, indicating that the NW major faults, Tesbahan、 Kulti and Basei faults in the research area dip to south at present and the thermal event of their reversed faulting directly controlled the regional tectonic evolution.