The evolution of the tectonic deformation of the northeastern Tibetan Plateau (TP) in the Cenozoic is significant for understanding plateau growth during India-Asia convergence. However, when deformation began and how it has developed in this pivotal region remain controversial. We focus on the temporal progress of Cenozoic deformation in the Qilian Shan, a major tectonic belt of the northeastern TP. In the present study, detrital apatite fission-track (AFT) thermochronological analysis was performed on Oligocene-Quaternary synorogenic sediments in the northern Qaidam Basin, where detritus is sourced from the Qilian Shan. Age components of buried but unannealed detrital AFT samples reveal two static peaks (i.e., peak ages that are consistent upsection) at ca. 60–50 Ma and ca. 40–36 Ma and a moving peak (i.e., peak ages that are younger upsection) with increased lag time during ca. 30–8 Ma. These new detrital AFT ages, integrated with the analysis of sedimentary provenance and data from previously published studies, indicate that Cenozoic tectonic deformation began in the Qilian Shan in the late Paleocene-early Eocene. Furthermore, the Qilian Shan experienced a subsequent episodic deformation event in the late Eocene and the deformation or erosion of some terranes in the Qilian Shan decelerated during the Oligocene-Miocene. Our results suggest that the northeastern TP responded to the India-Asia collision almost instantaneously.

中文翻译：

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青藏高原东北祁连山的新生代活化变形：碎屑磷灰石裂变径迹分析的启示

新生代东北部青藏高原（TP）的构造变形演化对于了解印度-亚洲融合过程中的高原增长具有重要意义。但是，何时开始变形以及在该关键区域如何变形仍然是有争议的。我们关注东北TP的主要构造带祁连山的新生代形变的时间进展。在本研究中，对柴达木盆地北部渐新世-第四系共生沉积物进行了碎屑磷灰石裂变径迹（AFT）热年代学分析，该碎屑来自祁连山。埋没但未退火的碎屑AFT样品的年龄成分显示出大约两个静峰（即，与上部一致的峰龄）。60-50 Ma左右。40–36 Ma和一个移动峰（即，上半部的峰值年龄）。30-8 Ma。这些新的碎屑AFT年龄与沉积物源分析和以前发表的研究数据相结合，表明新生代构造变形始于古新世-始新世晚期的祁连山。此外，祁连山在始新世晚期经历了随后的偶发性变形事件，在渐新世-中新世期间，祁连山的一些地层变形或侵蚀。我们的结果表明，东北TP几乎立即响应了印亚碰撞。这表明新生代的构造变形始于古新世晚期至始新世晚期的祁连山。此外，祁连山在始新世晚期经历了随后的偶发性变形事件，在渐新世-中新世期间，祁连山某些地层的变形或侵蚀受到了抑制。我们的结果表明，东北TP几乎立即响应了印亚碰撞。这表明新生代的构造变形始于古新世晚期至始新世晚期的祁连山。此外，祁连山在始新世晚期经历了随后的偶发性变形事件，在渐新世-中新世期间，祁连山的一些地层变形或侵蚀。我们的结果表明，东北TP几乎立即响应了印亚碰撞。