西昆仑山北缘新生代隆升历史的裂变径迹证据

发布时间：2018-03-21 15:32

  本文选题：西昆仑山　切入点：新生代　出处：《科学技术与工程》2017年33期 　论文类型：期刊论文

【摘要】：自新生代以来,西昆仑地区发生强烈的构造变形和隆升,其初始隆升和末次快速隆升的时限仍是有待探讨的重大问题。本文沿西昆仑北缘采集一系列砂岩样品,利用裂变径迹分析方法探讨了西昆仑北缘新生代的冷却历史。结合裂变径迹年龄和径迹长度分布进行分析,可以将6个磷灰石样品分为2组。3个磷灰石样品的径迹年龄远小于所在地层的年龄。平均径迹长度为(12.0±2.3)~(12.6±1.3)μm,呈不对称单峰形态,反映样品缓慢地通过部分退火带;另外3个磷灰石样品径迹年龄与各自地层的沉积年龄接近,平均径迹长度介于(10.7±2.3)~(11.4±1.3)μm,呈现双峰或混合分布的特征,表明沉积后发生部分退火。热史模拟显示,自晚白垩世以来,西昆仑山北缘共经历了3期抬升冷却事件。晚始新世(40~30 Ma),受早期印度板块向古亚洲大陆板块俯冲碰撞的影响,西昆仑山北缘已经开始隆升;晚渐新世 早中新世(25~15 Ma)是西昆仑乃至青藏高原重要的隆升时期;最后一轮强烈隆升则发生在距今5~3 Ma以来,冷却速率最高达15℃/Ma,剥蚀速率相当于600m/my。电子自旋共振测试揭示了早中新世(15 Ma)和晚上新世以来(2.6~0.63 Ma)两期强烈的构造变形和热液活动,更进一步限定了西昆仑最后一期强烈隆升在2.6 Ma以来。
[Abstract]:Since the Cenozoic, the tectonic deformation and uplift occurred strongly in the West Kunlun area, and the time limits of the initial uplift and the last rapid uplift are still important problems to be discussed. A series of sandstone samples were collected along the northern edge of the West Kunlun Mountains in this paper. The cooling history of the Cenozoic in the northern margin of West Kunlun is discussed by using the fission track analysis method, and the fission track age and track length distribution are analyzed. Six apatite samples can be divided into two groups. The track ages of 3 apatite samples are much smaller than that of the local layer. The average track length is 12.6 卤1.3 渭 m, which shows that the sample passes slowly through part of the annealing zone. The track ages of the other three apatite samples are close to their sedimentary ages, and the average track length is between 10.7 卤2.3 渭 m and 11.4 卤1.3 渭 m, showing a bimodal or mixed distribution, indicating partial annealing after deposition. The northern margin of the West Kunlun Mountains experienced three uplift and cooling events. The northern margin of the West Kunlun Mountains began to uplift due to the subduction and collision of the early Indian plate to the Paleo-Asian continental plate in the late Eocene. The late Oligocene and early Miocene were important uplift periods in West Kunlun and even the Qinghai-Xizang Plateau, and the last strong uplift occurred since 5 ~ 3 Ma ago. The cooling rate is up to 15 鈩，

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