河北东北部兴隆煤田区逆冲构造的特征及其区域构造意义

兴隆煤田及邻区的逆冲构造系基底卷入变形的厚皮逆冲构造,并具有典型的断坪-断坡式几何学结构.断层上盘逆冲方向指向NNW,沿着主干逆冲断层发生的倾向位移量约为13.1 km,逆冲断层及相关褶皱变形所造成的局部表层地壳缩短率约32.3%.对兴隆逆冲构造的几何学结构、运动学性质及其地层效应的分析表明,在申家胡同到黄土梁近东西向一线以南的区域,寻找到因逆冲断层作用导致的隐伏煤田的可能性是极小的.主干逆冲断层上、下盘地层大面积陡立乃至倒转的特征,更容易用断展褶皱,尤其是三角形剪切断展褶皱模型做出合理解释.该逆冲构造主要逆冲断层的上、下盘盖层岩系不整合于基底结晶变质岩系之上,地层序列发育完整而且可以一一对应,不存在沿着相对软弱层发育的大规模逆冲断层之断坪,因此,将该逆冲构造作为区域上承德逆冲构造的根带是不合适的.

Thrust tectonics in the Xinglong coalfield and adjacent areas, northeastern Hebei, China, and its implications for regional tectonics.

Thrust tectonics in the Xinglong coalfield and adjacent areas are characterized by basement-involved thick-skinned thrust tectonics with a typical flat-and-ramp geometry. The volume of displacement along the NNW-verging master thrust fault is estimated to be about 13.1 km and the shallower crustal shortening caused by the thrust and related folding is estimated to be around 32.3%. Based on an analysis of the geometry and kinematics of the thrust tectonics in this area, it is suggested that there is little probability to find a concealed coalfield in the area south of the nearly E-W-trending line from Shenjiahutong to Huangtuliang. The extensively steeply dipping and even overturned features of the strata in the hanging wall and footwaU of the major thrust fault are more easily rationally explained by basement-cored fault-propagation folding, especially by trishear fault-propagation folding model. The cover sequences in the hanging waU and footwaU of the major thrust fault unconformably overlie the crystalline metamorphic-series of the basement. They are completely developed and may be correlated. Neither thrust fault flat developed along the incompetent strata as suggested previously nor evidence for large-scale thrusting deformation has been found in this area. It is proposed that the Xinglong thrust could not serve as the root zone for the Chengde thrust found previously farther northward.