阿尔金-祁连山晚新生代隆升-剥露过程——来自岩屑磷灰石裂变径迹热年代学的制约

阿尔金-祁连山位于青藏高原北缘, 其新生代的隆升-剥露过程记录了高原变形和向北扩展的历史, 对探讨高原隆升动力学具有重要意义。本文采用岩屑磷灰石裂变径迹测年分析, 利用岩屑的统计特征限定阿尔金-祁连山新生代的隆升-剥露过程。磷灰石裂变径迹测试结果表明, 阿尔金-祁连山地区存在4个阶段的抬升冷却: 21.1~19.4 Ma、13.5~10.5 Ma、9.0~7.3 Ma、4.3~3.8 Ma。其中, 4.3~3.8 Ma抬升冷却事件仅体现在祁连山地区, 9.0~7.3 Ma抬升冷却事件在区内普遍存在, 且9.0~7.3 Ma隆升-剥露造就了现代阿尔金-祁连山的地貌。区域资料分析表明, 9~7 Ma(或者8~6 Ma)期间, 青藏高原北缘、东缘, 甚至整个中国西部地区发生了大规模、区域性的抬升, 中国现今"西高"的构造地貌形态可能于当时开始形成。阿尔金-祁连山地区4期抬升冷却事件与青藏高原的隆升阶段有很好的对应关系, 应该是对印度-欧亚板块碰撞的响应。

Late Cenozoic uplift-exhumation history of the Altyn Tagh and Qilian Mountains: Evidence from detrital apatite fission track thermochronology

The Altyn Tagh and Qilian Mountains define the northern boundary of the Tibetan Plateau. Their uplift-exhumation history in the Cenozoic records the deformation and northward propagation of the Tibetan Plateau, which is important to explore the uplift dynamics of the Tibetan Plateau. Using apatite fission track(AFT)analysis on detrital samples, this paper attempts to reveal Cenozoic uplift-exhumation history of the Altyn Tagh and Qilian Mountains statistically. AFT dating resuts suggest that the mountain ranges experienced four stages of uplift and cooling during the Late Cenozoic: 21.1~19.4 Ma, 13.5~10.5 Ma, 9.0~7.3 Ma, and 4.3~3.8 Ma. The youngest cooling event only took place within the Qilian Mountain. The uplift-exhumation of 9.0~7.3 Ma was perversive in the study area, resulting in the present geomorphology of Altyn Tagh and Qilian Mountains. Regional data show that a large-scale regional uplift of mountains in the northern and eastern edges of the Tibetan Plateau and even the whole western China occurred at 9~7 Ma(or 8~6 Ma)at which time the "high-west" landform of China was initially formed. The four uplift and cooling events are coeval with the uplift stages of the Tibetan Plateau, which should be response to the India-Eurasia collision.