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    吕梁山新生代隆升的裂变径迹证据及其隆升机制探讨

    Apatite fission track evidence for the Cenozoic uplift of the Lüliang Mountains and a discussion on the uplift mechanism

    • 摘要: 提要:从中生代大沉积盆地的一部分到现今南北向巨型山系且不同时代地质体平面上共存是吕梁山差异隆升、剥蚀的结果。为研究吕梁山隆升过程,在山体北、中、南地貌及地层突变部位进行了详细野外调查和基于磷灰石裂变径迹的热年代学研究。区域剥蚀厚度差异及“径迹年龄-高程”关系都表明地壳均衡隆升并非吕梁山隆升主导机制,受控于逆冲断裂的东-西向差异剥蚀及裂变径迹退火的空间变化规律共同证实南北向断裂的双向逆冲才是吕梁山差异隆升的动因。依据山体不同部位的裂变径迹年龄,可将吕梁山新生代隆升过程细分为(58±3)Ma、(40±3)Ma、(30±3)Ma、(23±3)Ma和(10±3)Ma 五个阶段:吕梁山新生代隆升起始于(58±3)Ma;此后,宁武断裂于(40±3)Ma启动,开启了差异隆升的序幕并奠定了吕梁山北段东部之主体格局;西部晋西挠褶带与吕梁断隆的差异剥蚀形成时间各不相同,北部不晚于(30±3)Ma,中段主要为(23±3)Ma,南段于(10±3)Ma得到进一步加强并形成明显的地势差。

       

      Abstract: Abstract:From part of huge sedimentary basin in Mesozoic to the present NS-treading gigantic mountains composed of geological bodies of various geological ages, there exists the product of uplift of Lüliang Mountains of different stages. Detailed field investigation and thermal chronologic study were carried out at the mutation positions of geomorphology and strata in north, middle and south sections of the mountains. The relationship of “age-depth” in apatite fission track and different erosion thicknesses in different parts of the mountains suggests that isostatic uplift was not responsible for the uplift of the Lüliang Mountains. EW-trending uneven erosion controlled by the thrust fault and distribution of annealing zone witnessed the fact that bilateral thrusts of NS-treading fault constituted the main uplift mechanism. According to the apatite fission track age from different parts of the Lüliang Mountains, the uplift can be subdivided into five stages, i.e., (58±3) Ma, (40±3) Ma, (30±3) Ma, (23±3) Ma and (10±3) Ma. The initial uplift originated from (58±3) Ma, then Ningwu fault began to form and resulted in the differential uplift pattern in the eastern part of North Lüliang Mountains. The differential erosion between Jinxi fault-fold belt and Lüliang Mountains block formed in different stages, the north was formed not later than (30±3) Ma, the middle was formed at (23±3) Ma, and the south was strengthened at (10±3) Ma.

       

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