Building the Pamir‐Tibetan Plateau—Crustal stacking, extensional collapse, and lateral extrusion in the Central Pamir: 2. Timing and rates
Building the Pamir‐Tibetan Plateau—Crustal stacking, extensional collapse, and lateral extrusion in the Central Pamir: 2. Timing and rates
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DOI：
10.1002/2016tc004294
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发表时间：
2017-03
期刊：
影响因子：
4.2
通讯作者：
D. Rutte;L. Ratschbacher;J. Khan;K. Stübner;B. Hacker;M. Stearns;E. Enkelmann;R. Jonckheere;J. Pfänder;B. Sperner;M. Tichomirowa
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文献类型：
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作者：
D. Rutte;L. Ratschbacher;J. Khan;K. Stübner;B. Hacker;M. Stearns;E. Enkelmann;R. Jonckheere;J. Pfänder;B. Sperner;M. Tichomirowa
地热年代学数据概述了帕米尔高原中部马斯科尔和沙普特片麻岩穹丘及其上盘的温度-变形-时间演化。前变质作用在~35 Ma之前开始，在~23-20 Ma达到顶峰，反映了顶部至~N逆冲席和褶皱推覆侵位，使亚洲地壳上部~7-10 km的厚度增加了两倍。多方法热年代学追踪了在~22 Ma和12 Ma之间由于沿沿着穹丘边界正向剪切带的折返作用而导致的~700-100°C的冷却。同运动矿物确定正常剪切带变形的年代为~22-17 Ma。年龄与海拔的关系和古等温线间距意味着折返≥3 km/Myr。在穹丘的南部，中生代花岗岩类记录了整个古近纪的缓慢冷却和/或恒温，以及从~23和12 Ma之间开始并持续到今天的增强冷却（7-31°C/百万年）。将中央帕米尔资料与东帕米尔公古尔山和慕兹塔格哈塔穹丘资料以及南帕米尔沙赫达拉穹丘资料相结合，表明（i）区域性分布的古近纪地壳增厚;（ii）在印度-亚洲正在进行的会聚过程中，帕米尔地区的增厚地壳重力塌陷始于~23-21 Ma;（3）≥12 Ma时，印度板块岩石圈向北扩展的俯冲作用结束，缩短作用恢复。帕米尔高原地壳向兴都库什和塔吉克凹陷的向西侧向挤压伴随着所有阶段。深层次的过程，例如，板块断裂、地壳沉降和浮力岩石圈的下冲作用，控制着帕米尔高原的过渡阶段，可能也控制着西藏地壳。
Geothermochronologic data outline the temperature‐deformation‐time evolution of the Muskol and Shatput gneiss domes and their hanging walls in the Central Pamir. Prograde metamorphism started before ~35 Ma and peaked at ~23–20 Ma, reflecting top‐to‐ ~N thrust‐sheet and fold‐nappe emplacement that tripled the thickness of the upper ~7–10 km of the Asian crust. Multimethod thermochronology traces cooling through ~700–100°C between ~22 and 12 Ma due to exhumation along dome‐bounding normal‐sense shear zones. Synkinematic minerals date normal sense shear‐zone deformation at ~22–17 Ma. Age‐versus‐elevation relationships and paleoisotherm spacing imply exhumation at ≥3 km/Myr. South of the domes, Mesozoic granitoids record slow cooling and/or constant temperature throughout the Paleogene and enhanced cooling (7–31°C/Myr) starting between ~23 and 12 Ma and continuing today. Integrating the Central Pamir data with those of the East (Chinese) Pamir Kongur Shan and Muztaghata domes, and with the South Pamir Shakhdara dome, implies (i) regionally distributed, Paleogene crustal thickening; (ii) Pamir‐wide gravitational collapse of thickened crust starting at ~23–21 Ma during ongoing India‐Asia convergence; and (iii) termination of doming and resumption of shortening following northward propagating underthrusting of the Indian cratonic lithosphere at ≥12 Ma. Westward lateral extrusion of Pamir Plateau crust into the Hindu Kush and the Tajik depression accompanied all stages. Deep‐seated processes, e.g., slab breakoff, crustal foundering, and underthrusting of buoyant lithosphere, governed transitional phases in the Pamir, and likely the Tibet crust.