大青山伸展拆离断层运动学涡度研究及构造指示意义  

Kinematic Vorticity of the Daqingshan Detachment Fault and its Structural Implications

作　　者：刘江[1] 张进江[1] 郭磊[2] 戚国伟[1] 

机构地区：[1]北京大学地球与空间科学学院,造山带与地壳演化教育部重点实验室,北京100871 [2]中国地质科学院地质研究所,北京100037

出　　处：《大地构造与成矿学》2011年第1期1-11,共11页Geotectonica et Metallogenia

基　　金：国家自然科学基金项目(90714006)成果

摘　　要：在华北北缘的大青山伸展拆离断裂带叠加在中生代逆冲断层之上,其韧性剪切带在变质核杂岩南北两侧出露,运动学指向为上盘向南东向拆离。运动学涡度分析表明,大青山拆离断层剪切带早期(较高温)简单剪切分量不断增加直至简单剪切;拆离断层总体平均涡度Wm简单剪切分量沿拆离断层上盘运动方向增大,与韧性剪切带先垂向颈缩、后水平伸展的被动式伸展有关。晚期(较低温)简单剪切分量降低、纯剪切分量增加,即拆离断层剥露过程中,脆韧性-脆性破裂面形成的变形分解导致纯剪切分量的增大。Kinematic vorticity （Wk） is defined to quantify the relative contributions of pure shear component and simple shear component in ductile deformation zone,and is a very important constraint on the evolution of a ductile shear zone. Ductile shear zone of the Daqingshan detachment fault which superimposed on the Mesozoic thrusts is exposed on both southern and northern limbs of Hohhot metamorphic core complex,with a top to south-east detachment direction. Kinematic vorticity analysis with different methods shows that the fault experienced a progressive increase of simple shear component until complete simple shear in the earlier stage （higher temperature）,0.94-1.00. Mean vorticy （Wm） increased along the direct of detachment,from 0.22-0.31 to 0.95-1.00,due to the thickening and thinning deformation transition. The northern part is at the centre of thrust and have a higher pure shear component. The simple shear component decreased while pure shear component increased in the later stage （lower temperature）,from 0.73-0.81. Pure shear component increases from ductile penetrative brittle-ductile-ductile stain partitioning during exhumation.

关 键 词：运动学涡度 伸展断层 构造意义 

分 类 号：P548[天文地球—构造地质学]