Building the Pamir‐Tibet Plateau—Crustal stacking, extensional collapse, and lateral extrusion in the Pamir: 3. Thermobarometry and petrochronology of deep Asian crust
Building the Pamir‐Tibet Plateau—Crustal stacking, extensional collapse, and lateral extrusion in the Pamir: 3. Thermobarometry and petrochronology of deep Asian crust
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DOI：
10.1002/2017tc004488
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发表时间：
2017-09
期刊：
影响因子：
4.2
通讯作者：
B. Hacker;L. Ratschbacher;D. Rutte;M. Stearns;Nicole Malz;K. Stübner;A. Kylander‐Clark;J. Pfänder;Alexa Everson
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文献类型：
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作者：
B. Hacker;L. Ratschbacher;D. Rutte;M. Stearns;Nicole Malz;K. Stübner;A. Kylander‐Clark;J. Pfänder;Alexa Everson
来自亚洲的结晶质中深层地壳岩石的巨大圆顶使帕米尔成为印度-亚洲碰撞的独特部分。结合主元素和微量元素温压法，伪截面，石榴石分区解构，和地质年代学被用来评估这些圆顶的埋藏和折返的历史。所有的圆顶被掩埋和加热到足以启动石榴石生长深度为15-20公里，在37-27马。帕米尔中央地区以每百万年约10-20°C的温度被加热，并以每百万年1-2公里的速度被掩埋，温度达到600-675°C，深度为25-35公里，时间为22-19 Ma。南帕米尔的沙赫达拉穹隆以每百万年约20°C的温度被加热，以每百万年2-8 km的速度被掩埋，在深度≥50 km时达到750-800°C，大约20 Ma。17-15 Ma时，所有圆顶都在>3 km/Myr至5-10 km深度和~300°C的温度下被挖出。压力、温度、埋藏速率和加热速率是大陆碰撞的典型特征。折返过程中的减压超过了冷却，与构造去顶沿着绘制的大规模正常方向剪切带相一致，并与近固相线或上固相线温度平流进入上地壳相一致，触发了与折返有关的岩浆活动。沙赫达拉穹隆是从比帕米尔中央穹隆更深的深度挖掘出来的，这可能是因为它位于古近纪后楔的腹地更远，以及印度板块断裂后的热量输入更高。在帕米尔和喀喇昆仑的广大地区，大规模的增厚和约20 Ma的同步切换到伸展加强了造山高原的演化受灾难性板块规模事件控制的观点。
Large domes of crystalline, middle to deep crustal rocks of Asian provenance make the Pamir a unique part of the India‐Asia collision. Combined major‐element and trace element thermobarometry, pseudosections, garnet‐zoning deconstruction, and geochronology are used to assess the burial and exhumation history of five of these domes. All domes were buried and heated sufficiently to initiate garnet growth at depths of 15–20 km at 37–27 Ma. The Central Pamir was then heated at ~10–20°C/Myr and buried at 1–2 km/Myr to 600–675°C at depths of 25–35 km by 22–19 Ma. The Shakhdara Dome in the South Pamir was heated at ~20°C/Myr and buried at 2–8 km/Myr to reach 750–800°C at depths of ≥50 km by ~20 Ma. All domes were exhumed at >3 km/Myr to 5–10 km depths and ~300°C by 17–15 Ma. The pressures, temperatures, burial rates, and heating rates are typical of continental collision. Decompression during exhumation outpaced cooling, compatible with tectonic unroofing along mapped large‐scale, normal‐sense shear zones, and with advection of near‐solidus or suprasolidus temperatures into the upper crust, triggering exhumation‐related magmatism. The Shakhdara Dome was exhumed from greater depth than the Central Pamir domes perhaps due to its position farther in the hinterland of the Paleogene retrowedge and to higher heat input following Indian slab breakoff. The large‐scale thickening and coincident ~20 Ma switch to extension throughout a huge area encompassing the Pamir and Karakorum strengthens the idea that the evolution of orogenic plateaux is governed by catastrophic plate‐scale events.