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《Acta Geologica Sinica》 2018-04
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Ductile Shearing Deformation and Geochronological Characteristics of the Huanghua-Tiejueshan Areas in the Northwestern Margin of the Sulu Orogen

LI Leilei;WANG Zongxiu;LI Chunlin;GAO Wanli;TAN Yuanlong;QIAN Tao;HU Junjie;LI Huijun;Key Laboratory of Shale oil and Gas Survey,Institute of Geomechanics,Chinese Academy of Geological Sciences;China University of Geosciences(Beijing);  
Experiencing multi-stage structural events,theSulu orogen currently presents current complex structural styles.The Huanghua-Tiejueshan areas,located in the northwestern margin of the Sulu orogeny,underwent intense structural deformation,and therefore formed an ENE-trending ductile shear zone.Therefore,study of the ductile shearing and geochronological characteristics of ductile shear zone will deepen understanding tectonic evolution of the Sulu orogen in late Mesozoic.In this paper,based on detailed field investigation and microstructure analysis,we analyzed the geometry and kinematic of shear zone and discussed the tectonic evolution of ductile shear zone combined with tectonic chronology.The results suggest that the ductile shear zone was geometrically shaped as an antiform and possibly experienced two stages of ductile shear deformation during the late Jurassic-early Cretaceous.(1)The early ductile deformation resulted from SEE-to NWW-trending near-horizontal detachment,accompanied by formation of pegmatite veins parallel to the attitude of the shear foliation.LA-ICP-MS zircon dating yielded an age of 150.1±1.1 Ma for the veins,indicating that the early ductile deformation initiated no later than 150 Ma.(2)The late ductile deformation was formed due to NNW-SSE trending extension.Simultaneously formed muscovite gives an plateau age of 137.09±0.32 Ma,which is consistent with the inverse isochron age.Moreover,undeformed dioritic porphyrite intruding into the ductile shear zone yields LA-ICP-MS U-Pb ages of 123.5±0.8 Ma and 127.1±1.6 Ma,indicating that the late ductile deformation started no later than 137 Ma and terminated prior to 127 Ma.Taking regional geological data into consideration,this study suggests that the early and late ductile deformation of the northwestern margin of the Sulu orogeny occurred at the late stage of intracontinental orogeny and post-orogenic extension,respectively.Two stages of tectonic activities reflect the tectonic regime transition in the Sulu orogeny.The tectonic regime transition possibly was closely related to subduction of paleo-pacific plate and crustal extension in eastern China during the late Mesozoic.
【Fund】: 中国地质调查项目(编号:1212011120965)资助的成果;中国地质调查项目(编号:DD20189614)联合资助的成果;; 国家重点研发计划项目(编号:2016YFC060020);; 国家自然科学基金项目(编号:41702204)
【CateGory Index】: P542;P597.3
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