秦岭太白山新生代隆升冷却历史的磷灰石裂变径迹分析

伸展正断层下盘的冷却历史记录了主要伸展变形的时间及幅度.太白山位于秦岭北缘,作为伸展正断层的下盘,其新生代伸展隆升冷却历史有助于我们更好地理解渭河盆地的伸展变形时间及其幅度.本文利用磷灰石裂变径迹分析方法对太白山的冷却历史进行了研究.来自太白山总计17个样品的磷灰石裂变径迹数据及热历史模拟揭示出山体经历了始于约48 Ma的小幅度快速抬升冷却阶段,和始于约9.6 Ma的大幅度快速抬升冷却阶段;分别对应平行于秦岭北缘山脉的两阶段伸展变形.始于约48 Ma的伸展变形可能是印度板块与欧亚板块碰撞作用在大陆内部的远场响应,而始于约9.6 Ma的快速伸展变形可能与青藏高原在该时期快速隆升和对外扩展有关.

The cooling history of Cenozoic exhumation and uplift of the Taibai Mountain,Qinling,China:evidence from the apatite fission track (AFT) analysis

The cooling history of footwall of extensional normal fault records the timing and magnitude of major extension. The Taibai mountain is located at the north edge of the Qinling mountains, as a mountain of normal fault growth and footwall flexture, its Cenozoic cooling history of extension-related exhumation and uplift can help us better understand the timing and magnitude of the extension of the Weihe Basin, a Cenozoic rift basin. In this paper, the AFT analysis method is used to research the Cenozoic cooling history of the Taibai mountain. The total seventeen AFT data from the Taibai mountain and the results of the representative fission track length models revealed that the Taibai mountain experienced two-phase cooling, the rapid cooling and small magnitude uplift starting at ~48 Ma and the late Cenozoic rapid cooling and large magnitude uplift starting at ~9.6 Ma; they correspond to the two-phase extension parallel to the north Qinling mountains starting at ~48 Ma and ~9.6 Ma, respectively. The extension starting at ~48 Ma could be caused by the far-field effect of the India-Eurasia collision at ~50 Ma, and the extension starting at ~9.6 Ma is considered to be related to the rising and northeastward growth of the Tibetan Plateau.