冀北承德地区张营子—六沟走滑断层及其构造意义

The Zhangyingzi—Liugou Strike-slip Fault in the Chengde Area of Northern Hebei Province and Its Tectonic Significance

笔者等运用构造解析的方法,在对冀北承德县一带的研究中鉴别出一条走向为北北西到北西向的右行走滑断层.断层将沿线太古宙古老变质岩、元古宇蓟县系、青白口系右行错断,它也将一个早期形成的短轴背斜构造带右行错断.位移距离沿断层向南南东方向逐渐减小,由15～16 km逐渐减小到12～13 km.断层截止于平泉-古北口断裂南侧元古宙逆冲岩片前缘,并将逆冲岩片南侧寒武系和奥陶系错动形成右行不对称牵引褶皱.由于断层使下三叠统丁家沟组变形而中三叠统胡杖子组却自西向东稳定延伸,所以笔者等认为断层形成的时代为早三叠世末.该走滑断层的存在表明,燕山板内造山带早期逆冲构造通过一些横向走滑断层的调节,呈板条状向南逆冲的.另外,前人所确定的'承德推覆体'上的元古宇与实际上在中三叠世以前与其东南侧的元古宇是连为一体的,由于北北西向右行走滑断层的错动使它们被右行错开.

Based on the basic principle of analytical structural geology, the authors identified a north-east strike-slip fault, which is perpendicular to the orogenic belt. This fault cut the Archean metamorphic rocks, Proterozoic Jixian system and Qingbaikou system along it and made the strata displaced in a dextral direction. It also made a short axis syncline belt, formed earlier during the late Paleozoic, displaced dextrally. The displacement distance of the fault decreases from 15-16 km to 12-13 km from north to south and the fault ends up in the front of the Proterozoic strata sheet to the south of the Pingquan-Gubeikou fault and made the Paleozoic strata fold. We named the fault the Zhangyingzi-Liugou fault in this paper. Because it made the Cambrian system and the Ordovician system folded, cut the short axial syncline belt formed during the late Paleozoic, and did not deform the upper and middle Triassic system and the low Jurassic system, the authors then deduced that the age of the fault is about the late early Triassic. The existence of the fault shows that the Chengde thrust plate does not exist in the area. In fact, the Proterozoic strata of the Chengde thrust plate, named in previous works, was connected originally with that located in the southeast of it and was cut and displaced by the early Mesozoic dextral strike-slip fault.