北京地区云蒙山变质核杂岩在白垩纪阶段抬升的早期,伴随着沿四合堂剪切带由北向南的拆离滑脱和大型花岗闪长岩的垂向侵位,晚期变形发生在花岗闪长岩岩基周边及其邻近围岩中,形成云蒙山剪切带,并伴随大量同构造的花岗岩和伟晶岩岩脉灌入。剪切带中所有的岩脉都随时间发生了不同程度的变形,较老的岩脉形成祭闭的圆柱状褶皱,枢纽与剪切带的线理和面理接近平行。岩脉与剪切带中L-S组构的平行化作用主要是由于这种转动的结果。岩脉的成分和长英指数随它们的变形程度发生变化,说明持续的岩浆分异作用与韧性剪切变形是同时发生的。云蒙山剪切带由岩浆底辟引起的上盘岩石重力所驱动,并不断得到同构造侵位岩脉的补充,起到存储和不断改造侵位岩脉的作用。早期伸展体制下形成的四合堂剪切带局部遭受云蒙山剪切带的改造或复合。该地区的岩石、构造和同构造岩脉的变形几何学和运动学证据表明,太古宙结晶基底的抬升是下部岩浆底辟与上部地壳伸展拆离共同作用的结果。
The uplift of the Yunmengshan metamorphic core complex in the Beijing region in the Cretaceous period was associated with a detachment southwards along the Sihetang shear zone and the emplacement of a large granodiorite batholith in an early stage. Subsequent deformation mainly occurred along the margins of the granodiorite batholith and its host rocks to form the Yunmengshan ductile shear zone, where abundant syntectonic granite and pegmatite veins injected into a mylonite zone. All of the veins in the shear zone were deformed with variable intensity during shear zone activity. The older veins are present as tight cylindrical folds, with fold axes orientated nearly parallel to the lineation and foliation of the shear zone. Parallelism between orientation of the veins and the L-S fabric in the shear zone resulted from the rotation of the veins during deformation. Composition and felsic index of the veins are found to be changing with their deformation intensity, suggesting that magmatic differentiation of the source was synchronous with deformation in the shear zone. The Yunmengshan shear zone is a gravitational detachment associated with magma diapirism, and was affected continuously by syntectonic veins intrusion, forming an effective reservoir and reworking site of the intruded veins. The Sihetang shear zone is an early stage extensional system that was reworked locally by the Yunmengshan shear zone. Petrological and regional scale tectonic evidence, geometric and kinematic data from the syntectonic deformed veins in the study area show that the uplift of the Archaean basement in the area resulted from a combination of magma diapirism and extensional detachment.