冀东高级变质区的构造特征──冀东太古宙地质问题讨论之三

按照韧性剪切带的发育程度，将区内划分为迁西群分布区的弱变形域和遵化群分布区的强变形带。根据各种形变特征，认为迁西群及遵化群分别存在三次及两次叠加褶皱，其中迁西期形成的为轴面南倾的东西向线状同斜褶皱；遵化期第一幕为北东向摆动的紧密线形倒转褶皱。由于边界条件的限制，叠加在迁西群上的褶皱，轴向转为近南北向。迁西期褶皱因属同斜而具简单层状体特征，故每个单体的叠加背向形并非三斜对称，主要部分也并非穹盆构造，而为ｗ形蛇形弯曲，不存在原生的穹隆或卵形群构造；遵化期第二幕表现为舒缓的东西向叠加褶皱。区内的主要构造样式为包括迁西群在内的由叠加褶皱及两组共轭韧性剪切带共同作用所形成的迂西－曹在卵形隆起区；遵化群的弧形褶皱群被密云－喜峰口－王厂左行平移韧性断裂带带动形成的宽城－遵化帚状构造亚区以及由遵化群形成的青龙王厂－迁安重熔片麻岩穹隆亚区。

Structural Character of High-grade Metamorphosed Area in the Eastern Hebei

According to the growth extent of ductile shear zone,the high-grade metamorphosedarea is divided into weakly deformed region of Qianxi Group and strongly deformed zone ofZunhua Group.Basing on the various characters of deformation, the authors recognized thatthe Qianxi Group and Zunhua Group existed respectively two or three superimposed folds,a-mong them,the Qianxi age was EW Iinear homoclinal fold with axial plane dipping to south;while the first episode of Zunhua age was appressed linear overturned fold stretching for NE,owing to the limit of boundary condition,the fold superimposed on Qianxi Group turned theiraxes to near SN. For the folds of Qianxi age was homoclinal and had simple-bedded, everysuperimposed anti-synform was not triclinic symmetry and the main part was not dome orbasin structure,but was W-shaped flexure,so there existed no primary structures of domesor ovals.The second episode of Zunhua age was EW stretched superimposed fold.Thus themain structure form of the region was a Qianxi-Caozhuang oval upwelling area,and wasformed by the common action of superimposed folds in Qianxi Group and two sets of conju-gated ductile shear zones,The arcuate folds of Zunhua Group had formed the Kuancheng-Zunhua brush structure subregion which was resulted from the dragging by Miyun-Xifengkou-Wangchang left-lateral displacement ductile fracture zone;and the other part of ZunhuaGroup had formed another subregion of Qinglong Wangchang-Qian'an remelting gneissdome.