银额盆地主要断裂带磁组构特征及其构造意义OA北大核心CSTPCD

As a basin formed during the evolution of the Central Asian Orogenic Belt,Yin'e Basin is an important prospective area for oil and gas resources in China.Influenced by the long⁃term activities of boundary faults such as the Beishan fault and the Langshan fault around the basin,Yin'e Basin exhibits a complex tectonic pattern of alternating uplift and depression in the northeast direction,with a central zone of both depression and uplift.The Altyn fault zone,Hongshishan fault zone,Engeerwusu fault zone and Jilantai fault zone,developed within the basin,control its formation and evolution.Using the tectonic⁃rock magnetic fabric method based on detailed field investigation,results show that tectonic fabric samples have two main characteristics of magnetic susceptibility:strong and weak.The shape parameters of magnetic fabric T(shape),magnetic foliation F and magnetic lineation L indicate that the magnetic susceptibility ellipsoid is predominantly flattened.The Flinn logarithm plot of elongated structural rock samples predominantly concentrates in the shear strain region,suggesting that the fracture zone experiences mainly compression and shear,with some minor tensile deformation.The orientation of Kmin,the main axis of minimum magnetic susceptibility,indicates that the principal stress direction in each fault zone is concentrated mostly in the NW⁃SE direction,corresponding to the basin's pattern of northeast⁃oriented uplift and depression.NWW and NE extensional deformations likely resulted from extensional collapse during tectonic regime transformation following subduction collision,consistent with the development of NE⁃SW trending rift basins.Local compressive forces in S⁃N and EW directions along the Engelwusu fault zone may be attributed to changes in the fault zone's local strike.