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北东走向、长达900km的依兰-伊通断裂带是东北地区重要的大型断裂构造,然而其起源问题却长期存在着较大的认识上分歧.通过系统的野外观察与室内综合分析,表明该断裂带在白垩-古近纪地堑外侧仍保存着走滑断层或韧性剪切带,代表了其起源期构造.这些走滑构造多为脆性平移断层,仅在南部威远堡-叶赫段和中部舒兰段出露为韧性剪切带.这两段剪切带走向北东-南西,具有陡倾的糜棱面理和缓倾的矿物拉伸线理.露头与显微构造及石英C轴组构均指示剪切带为左行走滑运动,并具有小幅度的逆冲分量.显微构造指示威远堡-叶赫段剪切带的变形温度为400~450℃,而舒兰段剪切带为350~400℃.一系列剪切带内变形与未变形岩体或岩脉的锆石U-Pb定年,限定了其走滑活动时限为160~126Ma.再依据研究区主要地质事件的对比,推断该断裂带起源时间为早白垩世初.由此表明,起源于中三叠世的郯庐断裂带中-南段,在早白垩世初区域挤压作用下(相当于燕山运动B幕)沿着依兰-伊通断裂带以左行平移断层的形式向北扩展进入东北地区.依兰-伊通断裂带在早白垩世初的出现应是东部太平洋区伊泽纳崎板块的高速斜向俯冲与西北部蒙古-鄂霍茨克洋最终关闭联合动力作用下的结果,但前者的动力贡献占主导.
The northeastward strike of Yilan-Yitong fault zone with a length of 900 km is an important large-scale fault structure in northeast China, but its origin has long had a big divergence in cognition. Through the systematic field observation and indoor comprehensive analysis, The fault zone still holds a strike-slip fault or ductile shear zone on the outer side of the Chalk-Paleogene, indicating its origin period structure. Most of these strike-slip structures are brittle translational faults. Only in the southern part of Weiyuanbao- Shulan and Central Shulan are exposed as ductile shear zones, which go north to southwest with steep mylonite and gentle dip mineral strata. Outcrops and microstructures and quartz The C-axis structure indicates that the shear zone is a left-lateral slip movement and has a small amplitude of thrust component.The microstructure indicates that the deformation temperature of the shear band of the Weiyuanbao-Yehe segment is 400-450 ℃, The segment shear band is 350-400 ° C. The zircon U-Pb dating of a series of shear-zone deformations and undeformed rocks or veins limits the strike-slip duration to 160-126 Ma, Geological events, infer the origin of the fault zone early Cretaceous .Therefore, originated in The middle-southern section of the Triangle in the Tan-Lu fault zone was expanded northward along the Ylang-Yitong fault zone in the form of a left-lateral translational fault during the early Cretaceous regional squeeze (equivalent to the B-axis of the Yanshan movement) Into the northeastern region.The occurrence of the Yilan-Yitong fault zone at the beginning of Early Cretaceous should be the result of a combination of high-speed oblique subduction of the Izanasaki plate in the eastern Pacific Ocean and a final closure of the Mongolia-Okhotsk ocean in the northwestern part , But the former’s power contribution dominates.