摘要
位于太行山中段井陉凹陷南缘、沿太古宙赞皇群片麻岩与上覆下元古界甘陶河群南寺掌组间不整合面附近发育的福庆寺(或苍岩寺)剪切带是一组复合型剪切带。根据其强应变带和罚变形域的特点可分为4个亚剪切带,它们的产出部位与构造间断面及岩性差异面有关。卷入翦切带的非能干岩层因变形变质作用普遍糜棱岩化,且具一定的分带性,边部为 S—C 糜棱岩,中心为强烈片理化糜棱岩(片糜岩),有时还出现千枚糜棱岩(千糜岩)。变形岩石中广泛发育具有指向意义的构造现象,如:不对称透镜状无根石英脉、不对称石英“布丁”或石香肠构造、肠状褶曲及转动现象等。因地台晚期的抬升隆起,围压、温度等条件的改变,在晚期差异地应力作用下,变形表现为脆性特点,以脆性断裂的方式叠加在早期韧性剪切变形带之上。福庆寺剪切带的形成和发展主要受三个因素的制约和控制:①已存的构造间断面(不整合面)和岩石的岩性差异和构造差异(块状与层状、巨厚一厚层与中薄层)面控制了剪切带的产出部位,②剪切带的变形深度控制了剪切带的变形性质;③地应力作用方式和地块的边界条件控制了剪切带的剪切运动方向。
The Fuqingshi shear zones,located at southern margin of the JingXing depression in the middle segment of the Taihangshan Mountains,are compound ones,Which occur in the vicinity of the unconformity between the gneisses of the Archean Zanhuang Group and low-metamorphic sedimentary rocks of the Nanshizhang Forma- tion,the Lower-Proterozoic Gantaohe Group.On the base of the features of intense deformation belts and weak deformation domain, the Fuqingshi shear zones can be divided into four sub-zones, which occurrences are related to the tectonic interruption and diffe- rential plane in rock property.The characteristics of ductile def- ormation and brittle deformation,superimposing onto the former, reflect the change of deformation behaviour of the shear zones with the formation and development of the North China Plateform in this area. The meta-sandstone or-siltstone and bedded meta-andesite invo- ved in the shear zones are generally milonitized due to deformation and metamorphism.Based on the texture and structure of the miloni- tes,they are probably classified into S-C milonite,which occurs near the both boundaryes of the shear zones,intense foliated milon- ite in the middle area of the zones,and phyllite milonite(or phyl- lonite) somewhere.Asymmetrically lenticular no-root quartz veins, asymmetric quartz boudins,ptygmatic folds and rotation in the mil- onites,which are idea indicators for the shear sense,are well deve- loped in the ductile shear zones.And the reason of that they show brittle might have been caused by the uplift of the plateform deriv- ing the decrease of pressure and temperature so that the later defor- mation is represented by the brittle faulting superimposes onto the earlier ductile shear zones. The formation and evalution of the Fuqingshi shear zones are restricted or controlled mainly by the following three factors:(1) the existed tectonic interruption (unconformity) and the differences of the rock structures (such as massive or bedded,thick-bedded to thin-bedded) and the difference of the rock properties,which control the extence of the shear zones;(2) the deformation depth of shear zones,which controls their properties;and (3) the manner of stresses acting and the boundary condition of the mass,which control the sense of shear movement.
