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    西昆仑山奇台达坂花岗岩锆石TIMS U-Pb测年及热演化历史分析

    Zircon TIMS U-Pb dating of the Qitaidaban granite in the West Kunlun Mountains and its thermal evolution history

      摘要
    • 摘要: 提要：应用锆石TIMS U-Pb测年获得西昆仑山奇台达坂花岗岩年龄为（202.2士3.4）Ma（MSWD=8.65）；利用不同海拔高度获得磷灰石裂变径迹测定年龄为24.8～14.0 Ma。通过裂变径迹热史模拟，并结合前人40Ar-39Ar测年数据，得出西昆仑山奇台达坂花岗岩就位以来，至少经历了三快二慢的冷却降温（隆升剥蚀）过程：即202.2～195.6 Ma、26～15 Ma和5 Ma以来3个阶段的快速降温（隆升剥蚀），195.6～26 Ma和15～5 Ma 2个阶段的缓慢冷却降温（隆升剥蚀）。西昆仑山地壳最上部约3 km的快速去顶作用主要发生于26～15 Ma和5 Ma以来，它是印度板块向欧亚板块碰撞的结果。

       

      Abstract: Abstract：TIMS U-Pb dating of zircons from the Qitaidaban granite in the West Kunlun Mountains yielded an age of 202.2±3.4 Ma (MSWD=8.65), and the apatite fission-track dating of samples taken at different altitudes yielded ages of 24.8-14.0 Ma. Fission-track thermal history modeling, combined with the previous data of 40Ar-39Ar dating, shows that the Qitaidaban granite underwent three rapid cooling stages (uplift and erosion) and two slow cooling stage (uplift and erosion) at least, i.e.: rapid cooling at 202.2-195.4 Ma, 26-15 Ma and since 5 Ma, and slow cooling at 195.4-26 Ma and 26-15 Ma. The rapid deroofing of the ～3 m thick topmost part of the crust below the West Kunlun Mountains took place at 26-15 Ma and since 5 Ma, which was the result of Eurasia-India collision.

       

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