卡拉麦里断裂带造山期活动规律及其对造山过程的指示

Orogeny-related Activities of Kalamaili Fault Zone and Their Indications to the Orogenic Processes

中亚造山带内东准噶尔地区北西西—南东东走向的大型卡拉麦里断裂带,为野马泉岛弧与哈尔里克岛弧之间的拼贴边界,沿卡拉麦里蛇绿岩带南缘出现。本文通过详细的野外与室内构造分析表明,这一倾向北北东的断裂带在造山期分别经历了脆—韧性右行走滑剪切和脆性逆冲活动。其脆—韧性剪切带在较软弱的板岩、砂板岩及浅变质凝灰岩内造成了密集的面理化带及张裂脉,而在泥灰岩内形成了糜棱岩。该剪切带的形成温度为250~300℃,与该区前二叠纪海相火山—碎屑岩的低级区域变质作用同时发生。该断裂带的第二期脆性逆冲活动主要表现上盘向南的逆冲,叠加的逆冲断层一方面沿着早期陡立的剪切带面理发育,另一方面以较缓的产状切割剪切带。各类地质现象指示,其脆—韧性右行走滑活动发生于晚石炭世中期,是野马泉岛弧与哈尔里克岛弧斜向碰撞的结果,并指示早期卡拉麦里洋盆向北俯冲。该断裂带的第二期逆冲活动发生于中二叠世,出现在该区后造山伸展之后,属于陆内变形,应为中亚造山带区域上一次中二叠世碰撞活动导致的。

Abstract： The large-scale NWW-striking Kalamaili fault zone in the eastern Junggar area is situated along the collision boundary between the Yemaquan and Harlik arcs, and along the southern margin of the Kalamaili ophiolite zone. On the basis of detailed field investigation and structural analysis, it is demonstrated that the NNE-dipping Kalamaili fault zone is subjected to earlier brittle--ductile dextral shearing and later brittle thrusting in the orogenic procesess. The more easily deformed rocks in the Kalamaili brittle--ductile shear zone, such as slate, sandy slate, and low-grade tuff, show densely foliation and tensile veins, and marls is deformed into mylonite. Deformation temperatures of the Kalamaili brittle--ductile shear zone is 250 - 300℃, and the shear zone development and regional low-grade metamorphism of pre-Permian volcanic--sedimentary rocks in this area occur at the same period. The second phase activity of the Kalamaili fault zone is top-to-the-south thrusting. The thrusts formed along the foliation of the earlier shear zone, or truncated the earlier shear zone. A variety of geological phenomena show that the Kalamaili brittle--ductile dextral shearing took place in the middle Late Carboniferous. The shear zone results from the oblique collision between Yemaquan arc and Harlik arc, which suggests that the Kalamaili oceanic plate subducted northwards. The Kalamaili brittle thrusts formed in the Middle Permian and belong to intracontinental deformation happening ＇after the post-collisional extension of the area. This phase of deformation should be related to the Middle Permian collision within the Central Asian Orogenic Belt .