郯庐断裂带北段构造样式解析

郯庐断裂带(郯城—庐江断裂带)北段在中—新生代发生多期不同性质活动,形成各具特色的构造样式.各种构造样式和地层间切割或覆盖关系的匹配研究,为限定断裂带活动期次及时代,建立郯庐断裂带北段变形序列提供了第一手资料.不同构造样式反映了断裂带由老至新经历了以下5个重要的变形事件:①密山县知—镇韧性剪切带黑云母40 Ar/39 ...

Analysis of Structural Styles in Northern Segment of Tancheng—Lujiang Fault Zone

Multiperiodic and diversely characteristic activities happened in the northern segment of the Tancheng—Lujiang fault zone in Meso—Cenozoic, which formed structural styles with various characteristics. The matching study of various structural styles and the relationship between stratigraphic cutting and coverage provides the first-hand information for limiting the active periods and era of the fault zone, establishing deformation sequence in the northern segment of the Tancheng—Lujiang fault zone.Different structural styles reflect that the fault zone from old one to new one has undergone the following five major deformation events: ① biotite 40Ar/39Ar isochron age of ductile shear zone near Zhiyi town,Mishan county is 161±3Ma, whichis the product of the Tancheng—Lujiang fault zone recurrence of large-scale sinistral strike-slip that extends to the Northeastern region; ② the negative flower faults of Yehe town,Siping city and the formation of the northeastern fault basin group in the early period of Early Cretaceous are the important basis for the northern segment of the Tancheng—Lujiang fault zone suffering from strong strike-slip and stretch in the early period of Early Cretaceous; ③ large-scale thrust zone and fault-related fold in Jiamusi—Yitong fault of Shiling town, Siping city, the "obsequent graben" in Dunhua—Mishan fault zone of Huadian City and Shenyang—Harbin thrust fault zone are the most obvious and wide-distributed structural styles in the northern segment of the Tancheng—Lujiang fault zone formed in the Nenjiang movement of later period of Late Cretaceous and last stage of Late Cretaceous, which reflects the northern segment of the Tancheng—Lujiang fault zone subjected to the extensive and strong right-lateral strike-slip thrusting activity; ④ Paleogene graben in Jiayi and Dunhua—Mishan is the product controlled by double machanism of right-lateral strike-slip and extension; ⑤ the tectonic inversion of Paleogene graben in late Oligocene put an end to the graben evolution; the upper mantle shearing in the northeast segment of the Tancheng—Lujiang fault zone in Miocene controls the Cenozoic volcanic crater containing mantle enclave regularly distributed along the fault.The above five major deformational events from the old to the new formed a relatively complete tectonic evolutionary sequence of the northern segment of the Tancheng—Lujiang fault zone, which are the products of the different geodynamic machanism.