敦密断裂带白垩纪两期重要的变形事件

本文报道了敦密断裂带糜棱岩中黑云母~(40)Ar/~(39)Ar定年结果和大规模走滑-逆冲断裂的几何学、运动学特征及其形成时代,以便揭示断裂带两期变形事件的构造属性。黑龙江省密山市花岗质糜棱岩中黑云母~(40)Ar/~(39)Ar加权平均年龄为132.2±1.2Ma,它是敦密断裂带经历伸展事件的冷却年龄,也是东北亚大陆边缘在早白垩世Hauterivian期-Albian期发生强烈区域伸展作用的产物。密山市至辽宁省清原县系列大型走滑-逆冲断层和断层相关褶皱揭示出在晚白垩世晚期-末期发生右旋走滑-逆冲事件,该事件规模大,影响范围广,导致整个断裂带遭受到强烈改造,形成对冲式断裂系统。将研究区走滑-逆冲断裂与山东省郯庐断裂带中段挤压构造对比,认为郯庐断裂带北段和中段在晚白垩世末期都发生了强烈的走滑-逆冲事件,它们具有相同的构造特征和构造属性。

Two important Cretaceous deformation events of the Dunhua-Mishan Fault Zone, NE China

This paper reports on the ⁴⁰Ar/³⁹Ar biotite age of the mylonites, the geometric and kinematic characteristics and forming age of large-scale strike-slip thrust faults in the Dunhua-Mishan Fault Zone, to reveal the tectonic attribute of two important deformation events in the fault zone. The ⁴⁰Ar/³⁹Ar weighted average age of biotite from the granitic mylonite in the Mishan City of Heilongjiang Province is 132.2±1.2Ma, which yields the cooling age of the extension event and it is the product of Cretaceous Hauterivian-Albian intensive regional extension in the continental margin of Northeast Asia. A series of large-scale strike-slip thrust faults and fault-related folds in the Mishan City to Qingyuan County of Liaoning Province indicate that the age of dextral strike-slip thrust event is in the late-end stage of Late Cretaceous. This large-scale event has a wide influence scope, which leads to an intensive reformation in the whole fault zone and forms a ramp type fault system. Comparing the strike-slip thrust faults in study area with compressional structures in the middle segment of the Tan-Lu Fault Zone in Shandong Province, we conclude that both the north and middle segment of the Tan-Lu Fault Zone underwent an intensive strike-slip thrust event in the latest stage of Late Cretaceous and they share a similar structural characteristics and tectonic attribute with each other.