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《Earth Science》 2018-07
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Documentation of Early Paleozoic Mafic Dykes in the Dahongshan Region,Northern Yangze Block and Its Geological Significance

Chen Chao;Yuan Jinling;Kong Lingyao;Ye Zhujun;Yang Qingxiong;Yang Cheng;Zhou Feng;Hubei Geological Survey;Hubei Institute of Geosciences;  
NE-SW mafic dykes are widespread in the Dahongshan region,northern Yangtze block.They mainly emplaced the pre-Nanhua basement rock,e.g.dolomite,sandstone and slate,and scarcely found in Nanhuan system and its overlying strata.It has been controversial for their formation age and background of the mafic dykes for a long time.In this paper,LA-ICP-MS zircon dating for 4 mafic dykes from Qilichong,Yaojiaju,Yaojiachong and Liuguan yield U-Pb ages of 433.7 Ma,435.6 Ma,433.4 Ma and 436.4 Ma respectively.All the ages belong to the Early Silurian and are consistent within measuring errors,and offer precise isotope chronology to the mafic dykes in the Dahongshan region.The mafic dykes in the Dahongshan region are characterized by subalkalic series,high ∑REE content,medium differentiation between LREE and HREE,enriched LILEs and depleted HFSEs,Zr100×10~(-6),TiO_22%,and Zr/Y3.5.Accordingly,it is suggested that they may have formed in a continental extension environment.We have discerned Early Paleozoic mafic dykes swarm indicative of continental extension in the northern Yangtze block for the first time.It provides powerful evidence that the Dahongshan region in the northern Yangtze block shows NE regional extension.Additionally,we tentatively thought that the south Qinling-Dabie mountain and the north Yangtze block belong to same extensional epicontinental rift environment although different sedimentary strata appearedbetween them in Early Paleozoic.
【Fund】: 中国地质调查局项目(No.121201009000160902);; 湖北省地质局科技项目(No.KJ2018-1)
【CateGory Index】: P534.4;P587
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