Late Paleozoic tectonic history of the Ertix Fault in the Chinese Altai and its implications for the development of the Central Asian Orogenic System
Late Paleozoic tectonic history of the Ertix Fault in the Chinese Altai and its implications for the development of the Central Asian Orogenic System
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DOI：
10.1130/b26044.1
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发表时间：
2007-07
影响因子：
4.9
通讯作者：
Stephanie M. Briggs;A. Yin;C. Manning;Zhengle Chen;Xiao-feng Wang;M. Grove
中科院分区：
文献类型：
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作者：
Stephanie M. Briggs;A. Yin;C. Manning;Zhengle Chen;Xiao-feng Wang;M. Grove
中亚造山带（CAOS）是世界上最大的显生宙增生造山带之一，可能是大陆生长的重要场所。它的起源被两种相互竞争的模式所解释：单个（约630 - 360 Ma）长寿命弧的同步俯冲走滑复制或多个弧和微大陆的碰撞。争论的核心是同俯冲走滑断层与逆冲断层的相对作用。在这两种模式中，Ertix断层都是突出的，要么是在大洋俯冲期间形成的大型走滑复式系统的顶断层，要么是弧-大陆或大陆-大陆碰撞的缝合。为了区分上述模型，我们对中国阿尔泰额尔提克斯断裂带进行了野外填图、详细的运动学分析和年代学测年。我们的研究表明，该断层是一个地壳规模的逆冲断层，活跃于二叠纪。其上壁记录了约450 Ma和280 Ma的两次岩浆活动脉冲，经历了6.2 - 7.7 kbar和560 - 670℃的峰值压力和温度。我们的地质观测和现有的地质资料支持这样一种构造模型，即阿尔泰弧以下有两期俯冲：第一次是在奥陶纪，沿南倾俯冲带；二是晚石炭世-早二叠世沿准噶尔洋北倾俯冲。正是在后者的活动中，一个混杂岩杂岩在古奥陶系弧下被下覆，在地壳深处变质，然后沿着向南的Ertix逆冲带向上地壳挖掘。
The Central Asian Orogenic System (CAOS) is one of the largest Phanerozoic accretionary orogens in the world and may represent a signifi cant site of continental growth. Its origin has been explained by two competing models: syn-subduction strikeslip duplication of a single (>1000 km) long-lived arc (ca. 630‐360 Ma) or collision of multiple arcs and micro-continents. Central to the debate are the relative roles of syn-subduction strike-slip faulting versus thrusting. In both models, the Ertix fault fi gures prominently, either as a roof fault of a large strike-slip duplex system developed during oceanic subduction or as a suture of arc-continent or continent-continent collision. In order to differentiate between the above models, we conducted fi eld mapping, detailed kinematic analysis, and geochronological dating of the Ertix fault zone in the Chinese Altai. Our work indicates that the fault is a crustal-scale thrust that was active in the Permian. Its hanging wall records two pulses of magmatism ca. 450 Ma and ca. 280 Ma and experienced peak pressure and temperature of 6.2‐7.7 kbar and 560‐ 670 °C. Our geologic observations, together with the existing geologic information, favor a tectonic model that involves two episodes of subduction below the Altai arc: fi rst, in the Ordovician, along a south-dipping subduction zone; and second, in the late Carboniferous and early Permian along northdipping subduction of the Junggar ocean. It was during the latter event that a melange complex was underplated below the older Ordovician arc, metamorphosed at lower crustal depths, and then exhumed to the upper crust along the south-directed Ertix thrust zone.