Cretaceous magmatic arc in Hainan and the peri-South China Sea asevidenced by geochemical fingerprinting of granitoids in the region  

作　　者：Xiao-Yan Jiang Yildirim Dilek Xian-Hua Li 

机构地区：[1]State Key Laboratory of Ore Deposit Geochemistry,Institute of Geochemistry,Chinese Academy of Sciences,Guiyang 550081,China [2]State Key Laboratory of Lithospheric Evolution,Institute of Geology and Geophysics,Chinese Academy of Sciences,Beijing 100029,China [3]Department of Geology and Environmental Earth Science,Miami University,Oxford,OH 45056,USA

出　　处：《Geoscience Frontiers》2024年第5期355-371,共17页地学前缘（英文版）

基　　金：supported by the Chinese National Natural Science Foundation(Grant No.41703010).

摘　　要：Mesozoic magmatic rocks occur widely in the South China Block and are generally interpreted as the manifestations of the subduction of the Paleo-Pacific oceanic lithosphere beneath Asia.Subductiondriven magmatism in southeast(SE)China continued from the Late Permian through the Late Cretaceous with an inferred lull between 125 Ma and 115 Ma that is known in the literature as the Cretaceous"magmatic quiescence".We report in-situ zircon U-Pb ages,Hf-O and whole-rock Sr-Nd isotopes,and whole-rock geochemistry of Cretaceous granitoids on Hainan Island and discuss their magmatic evolution within the framework of the Late Mesozoic geodynamics of SE China.We recognize two main stages of the emplacement of Cretaceous granitoids on Hainan,first around 120 Ma and then around 100-95 Ma,displaying high-K calc-alkaline,I-type geochemical affinities.Granites in both age groups are enriched in LILE and LREE,but depleted in Nb,Ta,Ba,Sr,and Eu.The 120 Ma granites have zircon ε_(Hf)(t)values of-2.6 to 2.3 corresponding to Hf crustal model ages,ranging from 0.79 Ga to 1.03 Ga,and δ^(18)O values ranging from 6.9‰to 7.7‰.Zircons from 100-95 Ma granites have ε_(Hf)(t)values of-4.2 to 1.1 corresponding to Hf crustal model ages of 1.08 Ga to 1.42 Ga,and δ^(18)O values ranging from 6.7‰to 8.4‰.Increasing ε_(Hf)(t)values of the Cretaceous Hainan granites with younger crystallization ages indicate addition of more juvenile components and reworking of crustal material into their melt evolution.The ε_(Nd)(t)values of the 120 Ma and 100-95 Ma granitoids range between-4.1 to-0.4 and-7.7 to-4.0,respectively.The calculated two-stage model age of the 100-95 Ma granitoids clusters between 1.25 Ga and 1.53 Ga.These isotopic data suggest that magmas of the Cretaceous granitoids were produced by partial melting of Mesoproterozoic metabasaltic rocks,which make up much of the crystalline basement of the southern Cathaysia block.The geochemical and isotopic characteristics of the Cretaceous granitoids on Hainan resemble those of magmatic a

关 键 词：I-type granites CRETACEOUS Hainan Island Southeast China Magmatic arc peri-South China Sea region 

分 类 号：P587[天文地球—岩石学] P59[天文地球—地质学]