呼和浩特变质核杂岩伸展运动学特征及剪切作用类型  

Extensional kinematics and shear type of the Hohhot metamorphic core complex,Inner Mongolia

作　　者：王新社[1] 郑亚东[1] 张进江[1] G.ADavis B.J.Darby 

机构地区：[1]北京大学地球与空间科学学院 [2]美国南加州大学地球科学系,洛杉矶ca900890740

出　　处：《地质通报》2002年第4期238-245,共8页Geological Bulletin of China

基　　金：国家自然基金项目"亚干变质核杂岩形成机制与构造演化"(编号:49872072);"赤峰娄子店低角断层系的性质及其三维构造分析"(编号:40102017);高校博士点专项科研基金项目(2000000128)资助。

摘　　要：叠加于大青山晚侏罗世大型推覆体之上的呼和浩特变质核杂岩具有与经典变质核杂岩相似的几何形态和构造组成。核杂岩表现为多重拆离,南翼主拆离断层系控制了山前坡地地貌,北翼拆离系发生褶皱并呈分叉状。糜棱状岩带中的线理、面理和拆离断层面及其擦痕等构造要素产状协调一致,宏观同向伸展褶劈理(C')产状与拆离断层一致,少数已扩展为断层;显微C'具有与宏观C'相似的特点,为同向伸展褶劈理扩展为低角断层提供了显微尺度依据。运动学标志,如不对称褶皱、不对称布丁、不对称眼球、S-C组构、石英条带斜交面理以及C'等,指示核杂岩拆离系发生了褶皱并且具有相同的上盘向南东的剪切运动。The Hohhot metamorphic core complex(MCC)superimposed on the large-scale Late Jurassic Daqingshan thrust nappe has a geometry and structure similar to those of the classic MCC.The Hohhot MCC is manifested by multiple detachments in time and space.The master detachment fault system at the southern side controls the geomorphology of the piedmont slopes,whereas the detachment system at the northern side is folded and sprays out.The lineation and foliation in the mylonitic zone and detachment fault and detachment fault surfaces and striations on the fault surfaces have concordant attitudes,which sug-gests that they formed synchronously.Macroscopic synthetic extensional crenulation cleavages(C' )have the same attitude as the detachment faults and a few of them have propagated into faults.Microscopic C' have similar characteristics to macroscopic C'.They can furnish micro-scale evidence for propagation of macro-scopic C' into low -angle normal faults.The kinematic indicators in the detachment system,such as sheared asymmetric folds,asymmetric boudinages,asymmetric augens ,S-C fabrics,oblique foliation in the quartz ribbons and C' ,reveal that the detachment system of the MCC was folded and sheared and show the same southeast-vergent shear of the hanging wall.

关 键 词：呼和浩特市 变质核杂岩 伸展运动学 剪切作用 类型 形成机制 

分 类 号：P588.3[天文地球—岩石学] P542[天文地球—地质学]