内蒙古西部狼山温更逆冲断层的地质特征

Geological characteristics of Wengeng thrust fault in Langshan area of western Inner Mongolia

内蒙古西部狼山温更逆冲断层发育在温更侏罗纪沉积盆地西北边界,是一条规模较大的逆冲断裂构造带。断层倾向北西,上盘由太古宙—元古宙变质地层和古生代深成侵入体构成,下盘为侏罗纪沉积,由北西向南东方向逆冲。断层切割改造了早--中侏罗世沉积地层,被早白垩世沉积地层覆盖,表明了逆冲断层形成在下中侏罗统沉积之后白垩系固阳组沉积之前。断层带同构造石英脉中流体包裹体的分析结果表明,断层形成于5.5～6km浅部地壳构造层之上,温度为195℃～210℃,围压为50～60MPa,断层带的宏观和显微构造显示断层以脆性变形机制为主。

Wengeng thrust fault in Langshan area of western Inner Mongolia developed at the northeastern boundary of Jurassic Wengeng sedimentary basin is a large thrust fault zone. The fault trends towards northwest, in which the hanging wall consists of Archean-Proterozoic metamorphic strata and Paleozoic plutonic intrusive body, and the footwall consists of Jurassic sediments, thrusting from northwest to southeast. The thrust fault cut and reformed the Early-Middle Jurassic sedimentary strata and is covered by the Early Cretaceous sedimentary strata, indicating that the thrust fault was formed between the deposition of Early-Middle Jurassic Series and Guyang Formation. The research of fluid inclusion of syntectonic quartz veins in fault zone proves that the thrust fault was formed in shallow structural level ranging from 5.5 km to 6 km, with temperature from 195℃ to 10℃, and the confining pressure from 50 MPa to 60 MPa. The macrostructure and microstructure of fault zone indicate the deformation of thrust fault was mainly brittle.