Structural evolution of the eastern segment of the Irtysh Shear Zone: Implications for the collision between the East Junggar Terrane and the Chinese Altai Orogen (northwestern China)
Structural evolution of the eastern segment of the Irtysh Shear Zone: Implications for the collision between the East Junggar Terrane and the Chinese Altai Orogen (northwestern China)
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DOI：
10.1016/j.jsg.2020.104126
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发表时间：
2020-10
影响因子：
3.1
通讯作者：
Wan-Long Hu;Pengfei Li;G. Rosenbaum;Junlai Liu;F. Jourdan;Yingde Jiang;Dan Wu;Jian Zhang
中科院分区：
文献类型：
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作者：
Wan-Long Hu;Pengfei Li;G. Rosenbaum;Junlai Liu;F. Jourdan;Yingde Jiang;Dan Wu;Jian Zhang
中亚造山带（CAOB）的构造演化涉及多幕弧增生/碰撞，但这些构造过程的重建仍然相对缺乏约束。在额尔齐斯剪切带东段（中国西北部）记录了东准噶尔地体洋内岛弧系与西伯利亚造山带（中国阿尔泰造山带）活动边缘碰撞的证据。在清河地区的野外观察表明，这段额尔齐斯剪切带由4条NW-SE向左行的糜棱岩带组成，以这些糜棱岩带为界的构造域具有不同的褶皱样式。在额尔齐斯剪切带北方（阿尔泰造山带南部），识别出三代构造（DCA 1-DCA 3）。最早世代的叶理（SCA 1）仅在局部被识别，并被转置到占优势的DCA 2叶理（SCA 2）的方向。后者与一个浅倾伸展线理有关，该线理与DCA 3褶皱的NW-SE枢纽近平行。这些第三代褶皱（DCA 3）显示了一个走向NW-SE的陡倾轴面。在额尔齐斯剪切带南部（东准噶尔地体北方），构造样式较简单，仅发育一个单世代的穿透叶理（SEJ 1）。新的U-Pb碎屑锆石和40 Ar/39 Ar数据提供了碰撞和变形时间的限制。这些结果表明，碰撞发生在早石炭世之后，左旋剪切的时间限制在早-中二叠世。左行剪切和北西-南东向DCA 3褶皱的组合可能代表了早-中二叠世东准噶尔地体与中国阿尔泰造山带斜向碰撞驱动的一幕压扭变形。原始近水平SCA 2叶理和与之相关的平行造山伸展线理的出现可能表明，在初始碰撞（早石炭世之后）之后，中国阿尔泰造山带南部受到了平行造山伸展。在更大的范围内，中国西北部和哈萨克斯坦东北部沿额尔齐斯剪切带的左行运动学沿着，以及更远的南部同时代的右行走滑变形，可能反映了造山物质向东逃逸，这可能是对西伯利亚、波罗的海和塔里木盆地二叠纪汇聚的响应。
The tectonic evolution of the Central Asian Orogenic Belt (CAOB) involved multiple episodes of arc accretions/collisions, but the reconstruction of these tectonic processes remains relatively poorly constrained. Evidence for a collision between the intra-oceanic island arc system of the East Junggar Terrane and the active margin of the Siberian Craton (Chinese Altai Orogen) is recorded in the eastern segment of the Irtysh Shear Zone (northwestern China). Field observations from the Qinghe area show that this segment of the Irtysh Shear Zone consists of four NW–SE sinistral mylonitic zones, and domains bounded by these mylonitic zones show variable fold patterns. In the northern part of the Irtysh Shear Zone (southern Chinese Altai Orogen), three generations of structures (DCA1–DCA3) are recognized. The earliest generation of foliation (SCA1) is only recognized locally and is transposed to the orientation of the dominant DCA2foliation (SCA2). The latter is associated with a shallowly plunging stretching lineation, which is sub-parallel to the NW–SE hinge of DCA3folds. These third-generation folds (DCA3) show a steeply-dipping axial plane trending NW–SE. In the southern part of the Irtysh Shear Zone (northern East Junggar Terrane), the structural pattern is simpler and only involves a single generation of penetrative foliation (SEJ1). New U–Pb detrital zircon and40Ar/39Ar data provide constraints on the timing of collision and deformation. These results suggest that the collision occurred after the Early Carboniferous, with the timing of sinistral shearing constrained to the Early–Middle Permian. The combination of sinistral shearing and NW–SE DCA3folds likely represents an episode of transpressional deformation, which was driven by oblique collision between the East Junggar Terrane and the Chinese Altai Orogen during the Early–Middle Permian. The occurrence of original sub-horizontal SCA2foliation and associated orogen-parallel stretching lineation might indicate that following the initial collision (after the Early Carboniferous), the southern Chinese Altai Orogen was subjected to orogen-parallel extension. In a larger-scale context, sinistral kinematics along the Irtysh Shear Zone in northwestern China and northeastern Kazakhstan, together with coeval dextral strike-slip deformation farther south, might reflect an eastward escape of orogenic materials, possibly in response to the Permian convergence of the Siberian, Baltic, and Tarim cratons.