Protolith ages and Indosinian deformation mechanism of metamorphic rocks in the Zhangbaling uplift segment of the Tan-Lu Fault Zone are important, unsolved problems. Our LA-ICP-MS zircon dating work indicates that pro...Protolith ages and Indosinian deformation mechanism of metamorphic rocks in the Zhangbaling uplift segment of the Tan-Lu Fault Zone are important, unsolved problems. Our LA-ICP-MS zircon dating work indicates that protolith ages of the greenschist-facies Zhangbaling Group are 754–753 Ma, and those of the amphibolite-facies Feidong Complex are 800–745 Ma. These rocks belong to the earliest cover of the Yangtze Plate. Their ages and metamorphic features suggest that the rocks did not come from the Dabie Orogen. The Indosinian structures in the Zhangbaling Group and lower Sinian strata formed in a flatlying ductile detachment zone with a shear sense of top-to-the-SSW whereas those in the underlying Feidong Complex are characterized by ENE-WSW inclined folds developed under a ductile regime. It is suggested therefore that the sinistral Tan-Lu Fault Zone of the Indosinian period is buried under the Hefei Basin west of the Zhangbaling uplift segment and the uplift segment is a displaced block neighboring the fault zone. Detachment deformation between the upper rigid and lower ductile crust during displacement of the Zhangbaling uplift segment resulted in the formation of the flat-lying ductile detachment zone and its underlying drag fold zone of a ductile regime. The protolith ages and deformation mechanism in the Zhangbaling uplift segment further prove sinistral origination of the Tan-Lu Fault Zone during the continent-continent collision of the North China and Yangtze plates and support the indentation model for the two-plate collision that considers the Tan-Lu Fault Zone as an oblique convergence boundary.展开更多
On the basis of comprehensive analyses of fault textures and geometry,the active methods,stress field,mechanism and time of the Yishu Fault Zone during the neotectonic period are discussed in this paper.The results sh...On the basis of comprehensive analyses of fault textures and geometry,the active methods,stress field,mechanism and time of the Yishu Fault Zone during the neotectonic period are discussed in this paper.The results show that the Yishu Fault Zone is a major mobile belt since the Quaternary.It consists of four major active faults with reverse dextral slip.Their active intensity increases eastwards and southwards.Fault-slip data from many active faults in the fault zone demonstrate that ENE-WSW compression predominated in the neotectonic period.Detailed field investigation shows that formation mechanism of shallow,active faults in the Yishu Fault Zone includes direct boundary fault reactivity,buried fault propagation,and reactivity of antithetic and truncating faults.In most cases,shallow,active faults in the fault zone are developed through direct reactivity or upward propagation of the previous four graben boundary faults.展开更多
Early deformation history of the Yanshan Tectonic Belt is an unsolved,important issue.We report early structures and their dating results in basement rocks south of the Kalaqin metamorphic core complex.The basement de...Early deformation history of the Yanshan Tectonic Belt is an unsolved,important issue.We report early structures and their dating results in basement rocks south of the Kalaqin metamorphic core complex.The basement deformation zone is characterized by WNW-ESE steep gneissosity,WNW-ESE shallow mineral elongation lineation and many intrafolial or isoclinal folds.Many kinematic indicators show that it is a WNW-ESE steep,ductile sinistral deformation zone.LA-ICPMS zircon dating gives a crystallization age of 271 Ma for tatolly transposed,deformed monzonite granite dyke and crystallization ages of 251–250 Ma and210 Ma for undeformed dyke,stock and pluton.The dating results demonstrate that the deformation related to regional shortening took place between 271 and 251 Ma,i.e.Middle-Late Permian.Combined with previous dating results for post-orogenic magmatism in the Yanshan Tectonic Belt,it is inferred that the shortening-related deformation happened in Middle Permian(271–260 Ma).Recent studies suggest that collision along the Solonker Suture took place in Middle Permian,and is then followed by post-collision extenion in Late Permian.We propose that the intense shortening deformation of the Middle Permian in the Yanshan Tectonic Belt belongs to foreland deformation along the norterhn margin of the North China Craton which is caused by continent-continent collision in the Xing-Meng Orogen.The belt was then oriprinted by shortening deformation of the Yanshanian Movement.展开更多
基金supported by the National Natural Science Foundation of China(Grant Nos.41072162,91214301)
文摘Protolith ages and Indosinian deformation mechanism of metamorphic rocks in the Zhangbaling uplift segment of the Tan-Lu Fault Zone are important, unsolved problems. Our LA-ICP-MS zircon dating work indicates that protolith ages of the greenschist-facies Zhangbaling Group are 754–753 Ma, and those of the amphibolite-facies Feidong Complex are 800–745 Ma. These rocks belong to the earliest cover of the Yangtze Plate. Their ages and metamorphic features suggest that the rocks did not come from the Dabie Orogen. The Indosinian structures in the Zhangbaling Group and lower Sinian strata formed in a flatlying ductile detachment zone with a shear sense of top-to-the-SSW whereas those in the underlying Feidong Complex are characterized by ENE-WSW inclined folds developed under a ductile regime. It is suggested therefore that the sinistral Tan-Lu Fault Zone of the Indosinian period is buried under the Hefei Basin west of the Zhangbaling uplift segment and the uplift segment is a displaced block neighboring the fault zone. Detachment deformation between the upper rigid and lower ductile crust during displacement of the Zhangbaling uplift segment resulted in the formation of the flat-lying ductile detachment zone and its underlying drag fold zone of a ductile regime. The protolith ages and deformation mechanism in the Zhangbaling uplift segment further prove sinistral origination of the Tan-Lu Fault Zone during the continent-continent collision of the North China and Yangtze plates and support the indentation model for the two-plate collision that considers the Tan-Lu Fault Zone as an oblique convergence boundary.
基金supported by National Natural Science Foundation of China(Grant No.91214301)Geological Survey of China(Grant No.1212011120104)
文摘On the basis of comprehensive analyses of fault textures and geometry,the active methods,stress field,mechanism and time of the Yishu Fault Zone during the neotectonic period are discussed in this paper.The results show that the Yishu Fault Zone is a major mobile belt since the Quaternary.It consists of four major active faults with reverse dextral slip.Their active intensity increases eastwards and southwards.Fault-slip data from many active faults in the fault zone demonstrate that ENE-WSW compression predominated in the neotectonic period.Detailed field investigation shows that formation mechanism of shallow,active faults in the Yishu Fault Zone includes direct boundary fault reactivity,buried fault propagation,and reactivity of antithetic and truncating faults.In most cases,shallow,active faults in the fault zone are developed through direct reactivity or upward propagation of the previous four graben boundary faults.
基金supported by the National Natural Science Foundation of China (91214301)
文摘Early deformation history of the Yanshan Tectonic Belt is an unsolved,important issue.We report early structures and their dating results in basement rocks south of the Kalaqin metamorphic core complex.The basement deformation zone is characterized by WNW-ESE steep gneissosity,WNW-ESE shallow mineral elongation lineation and many intrafolial or isoclinal folds.Many kinematic indicators show that it is a WNW-ESE steep,ductile sinistral deformation zone.LA-ICPMS zircon dating gives a crystallization age of 271 Ma for tatolly transposed,deformed monzonite granite dyke and crystallization ages of 251–250 Ma and210 Ma for undeformed dyke,stock and pluton.The dating results demonstrate that the deformation related to regional shortening took place between 271 and 251 Ma,i.e.Middle-Late Permian.Combined with previous dating results for post-orogenic magmatism in the Yanshan Tectonic Belt,it is inferred that the shortening-related deformation happened in Middle Permian(271–260 Ma).Recent studies suggest that collision along the Solonker Suture took place in Middle Permian,and is then followed by post-collision extenion in Late Permian.We propose that the intense shortening deformation of the Middle Permian in the Yanshan Tectonic Belt belongs to foreland deformation along the norterhn margin of the North China Craton which is caused by continent-continent collision in the Xing-Meng Orogen.The belt was then oriprinted by shortening deformation of the Yanshanian Movement.
