SEISMOLOGY AND GEOLOGY ›› 2020, Vol. 42 ›› Issue (2): 472-491.DOI: 10.3969/j.issn.0253-4967.2020.02.014

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LI Jia-yu1,2), ZHENG Wen-jun1,2), WANG Wei-tao1,2), WAN Ying3), ZHANG Pei-zhen1,2), WANG Yang1,2)   

  1. 1)School of Earth Sciences and Engineering, Sun Yat-sen University, Guangzhou 510275, China;
    2)Southern Marine Science and Engineering Guangdong Laboratory(Zhuhai), Zhuhai 519082, China;
    3)State Key Laboratory of Earthquake Dynamics, Institute of Geology, China Earthquake Administration, Beijing 100029, China
  • Received:2019-12-31 Online:2020-04-20 Published:2020-07-13


李佳昱1,2), 郑文俊1,2),*, 王伟涛1,2), 王英3), 张培震1,2), 王洋1,2)   

  1. 1)中山大学地球科学与工程学院, 广东省地球动力作用于地质灾害重点实验室, 广州 510275;
    2)南方海洋科学与工程广东省实验室(珠海), 珠海 519082;
    3)中国地震局地质研究所, 地震动力学国家重点实验室, 北京 100029
  • 通讯作者: * 郑文俊, 男, 1972年生, 教授, 博士生导师, 从事新构造、 活动构造与构造地貌研究, E-mail:。
  • 作者简介:李佳昱, 女, 1994年生, 2017年于长安大学地球科学与资源学院获地质学学士学位, 主要从事新构造、 低温热年代学方面的研究, E-mail:。
  • 基金资助:
    第二次青藏高原综合科学考察(2019QZKK0901)、 国家自然科学基金(41590861, 41872204, 41674051)和广东省引进人才创新团队(2016ZT06N331)资助

Abstract: Longshou Shan, located at the southern edge of the Alxa block, is one of the outermost peripheral mountains and the northeasternmost area of the northeastern Tibetan plateau. In recent years, through geochronology, thermochronology, magnetic stratigraphy and other methods, a large number of studies have been carried out on the initiation time of major faults, the exhumation history of mountains and the formation and evolution of basins in the northeastern Tibet Plateau, the question of whether and when the northeastward expansion of the northeastern Tibet Plateau has affected the southern part of the Alxa block has been raised. Therefore, the exhumation history of Longshou Shan provides significant insight on the uplift and expansion of the Tibetan plateau and their dynamic mechanism. The Longshou Shan, trending NWW, is the largest mountain range in the Hexi Corridor Basin, and its highest peak is more than 3 600m(with average elevation of 2800m), where the average elevation of Hexi Corridor is 1 600m, the relative height difference between them is nearly 2200m. This mountain is bounded by two parallel thrust faults: The North Longshou Shan Fault(NLSF)and the South Longshou Shan Fault(SLSF), both of them trends NWW and has high angle of inclination(45°~70°)but dips opposite to each other. The South Longshou Shan Fault, located in the northern margin of the Hexi Corridor Basin, is the most active fault on the northeastern plateau, and controls the uplift of Longshou Shan.Due to its lower closure temperature, the lower-temperature thermochronology method can more accurately constrain the cooling process of a geological body in the upper crust. In recent years, the low-temperature thermochronology method has been used more and more in the study of the erosion of orogenic belts, the evolution of sedimentary basins and tectonic geomorphology. In this study, the apatite (U-Th)/He(AHe) method is used to analyze the erosion and uplift of rocks on the south and north sides of Longshou Shan. 11 AHe samples collected from the south slope exhibit variable AHe ages between~8Ma and~200Ma, the age-elevation plot shows that before 13~17Ma, the erosion rate of the Longshou Shan is very low, and then rapid erosion occurs in the mountain range, which indicates that the strong uplift of Longshou Shan occurred at 13~17Ma BP, resulting in rapid cooling of the southern rocks. In contrast, 3 AHe ages obtained from the north slope are older and more concentrated ranging from 220Ma BP to 240Ma BP, indicating that the north slope can be seen as a paleo-isothermal surface and the activity of the north side is weak. The results of thermal history inverse modeling show that the South Longshou Shan Fault was in a tectonic quiet period until the cooling rate suddenly increased to 3.33℃/Ma at 14Ma BP, indicating that Longshou Shan had not experienced large tectonic events before~14Ma BP.
    We believe that under the control of South Longshou Shan Fault, the mountain is characterized by a northward tilting uplift at Mid-Miocene. Our results on the initial deformation of the Longshou Shan, in combination with many published studies across the northeastern margin of the Tibetan plateau, suggest that the compression strain of the northeastern margin of the Tibetan plateau may expand from south to north, and the Tibetan plateau has expanded northeastward to the southern margin of the Alxa block as early as Mid-Miocene, making Longshou Shan the current structural and geomorphic boundary of the northeastern plateau.

Key words: apatite(U-Th)/He, mountain range uplift, plateau growth, Longshou Shan, northeastern Tibetan plateau

摘要: 龙首山位于阿拉善地块南缘, 也是青藏高原东北部最外围的山脉之一。 揭示龙首山新生代构造变形与隆升过程对于理解青藏高原东北部的隆升与向外扩展及其动力学机制具有重要意义。 文中利用磷灰石(U-Th)/He方法, 对青藏高原东北部龙首山南、 北两侧岩石的侵蚀与隆升过程开展研究。 采集自龙首山南缘的11个磷灰石的(U-Th)/He年龄结果显示, 在其南缘断层的控制下, 龙首山约于14Ma BP发生了强烈隆升或剥蚀, 导致上部岩石快速冷却。 而在龙首山北缘采集的3个样品的年龄较老(220~240Ma), 但年龄非常相近, 表明其北侧活动较弱, 龙首山整体表现为掀斜模式。 龙首山中中新世由南向北的掀斜式抬升不仅揭示了青藏高原东北部挤压应变可能由南向北扩展, 同时也限定了青藏高原在中中新世已向NE扩展至阿拉善地块南缘, 使龙首山成为高原东北部现今构造与地貌的边界。

关键词: 磷灰石(U-Th)/He, 山脉隆升, 高原扩展, 龙首山, 青藏高原东北部

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