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《Earth Science(Journal of China University of Geosciences)》 2009-01
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U-Pb Ages and Hf Isotopes of Detrital Zircons of Nanhua Sedimentary Rocks from the Yangtze Gorges:Implications for Genesis of Neoproterozoic Magmatism in South China

XIE Shi-wen1,2,GAO Shan1,2,3,LIU Xiao-ming3,GAO Ri-sheng41.Faculty of Earth Sciences,China University of Geosciences,Wuhan430074,China2.State Key Laboratory of Geological Processes and Mineral Resources,China University of Geosciences,Wuhan430074,China3.State Key Laboratory of Continental Dynamics,Department of Geology,Northwest University,Xi'an710069,China4.CNPC International Research Center,Beijing100083,China  
This paper reports LA-ICP-MS U-Pb dates of detrital zircons from the Nanhua clastic sedimentary rocks in the Yangtze gorges.Neoproterozoic U-Pb ages show two peaks at 833Ma and 785Ma,assumably corresponding to two large-scale periods of magmatism.εHf(t)values for the 910-890Ma zircons are positive(≈10,similar to the value of the coeval depleted mantle),while those for the 890-840Ma zircons tend to decrease to negative values,and there shows age peaks at 890Ma.These data allow us to infer that transformation of oceanic subduction into continental collision or continental-arc collision occurred at about 890Ma via amalgamation of the Yangtze and Cathaysia blocks.The high εHf(t)values prior to 890Ma resulted from the subduction of oceanic crust.The subsequent drop of εHf(t)values was caused by the crust melting and crustal collision.εHf(t)values for the 840-800Ma zircons are either negative or positive,whereas εHf(t)values for the 800-780Ma zircons are all negative and εHf(t)values for the 780-750Ma zircons are mostly positive.These data are in coincidence with two stages of the mantle plume beneath the Yangtze craton at 830-795Ma and 780-745Ma.
【Fund】: 教育部创新团队研究计划项目(Nos.IRT0441 306021);; 国家自然科学基金委创新研究群体科学基金项目(No.40521001);; 高等学校学科创新引智计划(No.B07039)
【CateGory Index】: P597.3
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