大兴安岭北部漠河韧性剪切带白云母40Ar-39Ar年龄及地质意义

^(40)Ar-^(39)Ar dating of the muscovite in the mylonite of the Mohe ductile shear zone in northern Da Hinggan mountain and its geological significance

漠河韧性剪切带位于大兴安岭北部上黑龙江盆地内。作者对该韧性剪切带糜棱岩中白云母样品进行了40Ar-39Ar法测定年龄工作,获得了(120.6±1.1)Ma的坪年龄和(121.7±1.5)Ma的39Ar/36Ar-40Ar/39Ar等时线年龄,表明其形成于早白垩世。结合韧性剪切带特征,笔者认为漠河韧性剪切带与蒙古-鄂霍茨克造山带的造山过程有关,形成于蒙古-中朝板块与西伯利亚板块之间的陆-陆碰撞造山阶段的晚期或后碰撞期间。早白垩世期间,蒙古-鄂霍茨克造山带进入后碰撞阶段,发生大规模左行走滑运动,使位于蒙古-鄂霍茨克缝合带南部的中国东北地区,乃至华北北部发生了向东的挤出、逃逸,辽西、冀北、冀西北和京西地区的晚中生代右行走滑和逆冲、推覆构造是蒙古-鄂霍茨克中生代造山过程的远程效应。因此,蒙古-鄂霍茨克造山带造山过程对中国东北及华北地区中生代期间的构造演化具有重要影响。

The Mohe ductile shear zone is located in the Shang Heilongjiang basin of the northern Da Hinggan mountain in China. The authors have dated the muscovite in the mylonite of the ductile shear zone by the 40Ar-39Ar technique and obtained 4o Ar39 Ar plateau age of （120.6±1. 1） Ma and 39 Ar/ 36Ar-40Ar/39Ar isochron age of （121. 7± 1. 5） Ma, respectively. The dating result shows that the ductile shear zone formed in early Cretaceous. Combining the field characteristics of the ductile shear zone, the authors think that the Mohe ductile shear zone formed in the late phase or post-collision phase of the continent-continent collisional orogeny between the Siberia and Mongolia-Sinokorea continents and its formation is related to Mongolia-Okhotsk orogeny. In early Cretaceous, the evolution of the Mongolia-Okhotsk orogeny went into post-collisional stage, and a sinistral strike slip took place, indicating that Northeast China and even the northern part of North China located to the south of the Mongolia-Okhotsk suture were sneezed out eastwardly. The late Mesozoic dextral strike slip, thrust and nappe structures in western Liaoning, northern Hebei, northwestern Hebe and western Beijing are the long-range effect of the Mongolia-Okhotsk orogeny. Consequently, the Mongolia-Okhotsk orogeny has an important effect on the Mesozoic tectonic evolution of Northeast China and North China.