Pre-cenozoic evolution of the northern Qilian Orogen from zircon geochronology: Framework for early growth of the northern Tibetan Plateau
Pre-cenozoic evolution of the northern Qilian Orogen from zircon geochronology: Framework for early growth of the northern Tibetan Plateau
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DOI：
10.1016/j.palaeo.2020.110091
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发表时间：
2020-10
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通讯作者：
Bing Li;A. Zuza;Xuanhua Chen;Zeng-Zhen Wang;Z. Shao;D. Levy;Chen Wu;Shenglin Xu;Yujun Sun-Yujun
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文献类型：
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作者：
Bing Li;A. Zuza;Xuanhua Chen;Zeng-Zhen Wang;Z. Shao;D. Levy;Chen Wu;Shenglin Xu;Yujun Sun-Yujun
沿着青藏高原东北缘的北方祁连山，在整个中生代经历了多期造山运动，并以与新生代印度-亚洲碰撞有关的褶皱-逆冲-走滑变形为高潮。祁连山早期的变形被最近的新生代应变严重地重新激活或改造。为了更好地了解这一复杂地区的构造演化，我们进行了综合调查的野外观察，火成岩和碎屑锆石U-Pb测年，并综合以前发表的数据，以限制和重建前新生代的历史北方祁连山。这一努力揭示了对该地区历史重要的五个主要年龄人口：2550-2350，1850-1750，1050-950，500-435和320-240 Ma。使用这个数据集，我们确定了三个主要的沉积变化和/或排水模式的变化，影响沉积物来源的北方祁连造山带。区域地质约束，岩浆历史，和新的地球物理观测的深部结构，使我们能够提出一个连贯的构造模式的前新生代演化的青藏高原东北缘。(1)新元古代晚期至寒武纪裂谷作用打开了祁连洋。(2)早寒武世沿着柴达木和华北-塔里木陆缘俯冲作用的启动，导致寒武-奥陶纪两次俯冲，两陆内弧岩浆活动，祁连洋被消耗。(3)最后的海洋闭合和大陆碰撞发生在约。440 Ma，与同造山期和造山后岩浆活动有关。(4)碰撞造山作用侵蚀了基底岩石，重组了水系网络，并改变了下古生代至上古生界沉积物的沉积物源。(5)中生代伸展作用导致了巨厚的侏罗-白垩纪陆相盆地的发育。这种前新生代的历史导致了预先存在的弱点和/或低摩擦拆离层位，在控制整个北方青藏高原新生代变形的模式、分布和时间方面起着决定性的作用。
The northern Qilian Shan, located along the northeastern margin of the Tibetan Plateau, experienced multiple phases of orogeny throughout the Phanerozoic, culminating in fold-thrust and strike-slip deformation associated with the Cenozoic India-Asia collision. Earlier phases of deformation in the Qilian Shan have been severely reactivated or transformed by the most recent Cenozoic strain. To better understand the tectonic evolution of this complex region, we conducted an integrated investigation of field observations, U–Pb dating of igneous and detrital zircons, and a synthesis of previously published data to constrain and reconstruct the pre-Cenozoic history of the northern Qilian Shan. This effort reveals five major age populations important to the history of this region: 2550–2350, 1850–1750, 1050–950, 500–435, and 320–240 Ma. Using this dataset, we identified three major depositional shifts and/or variations in drainage patterns that affected sediment provenance of the northern Qilian Orogen. Observed regional geologic constraints, the magmatic history, and new geophysical observations of the deep structure allow us to propose a coherent tectonic model for the pre-Cenozoic evolution of the northeastern margin of the Tibetan Plateau. (1) Late Neoproterozoic to Cambrian rifting opened the Qilian Ocean. (2) Early Cambrian subduction initiation along the margins of Qaidam and North China–Tarim continents resulted in Cambrian-Ordovician bivergent subduction, arc magmatism within these two continents, and consumption of the Qilian Ocean. (3) Final ocean closure and continental collision occurred at ca. 440 Ma and was associated with syn- and post-orogenic magmatism. (4) Collisional orogeny variably eroded the basement rocks, reorganized drainage networks, and altered sedimentary provenance for the lower Paleozoic to upper Paleozoic deposits. (5) Mesozoic extension led to the development of thick Jurassic–Cretaceous terrestrial basins. This pre-Cenozoic history resulted in preexisting weaknesses and/or low-friction detachment horizons that played a decisive role in controlling the pattern, distribution, and timing of Cenozoic deformation across the northern Tibetan Plateau.