首页|Cretaceous magmatic arc in Hainan and the peri-South China Sea as evidenced by geochemical fingerprinting of granitoids in the region
Cretaceous magmatic arc in Hainan and the peri-South China Sea as evidenced by geochemical fingerprinting of granitoids in the region
扫码查看
点击上方二维码区域，可以放大扫码查看
原文链接
NETL
NSTL
万方数据
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.Subduction-driven 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 iso-topes,and whole-rock geochemistry of Cretaceous granitoids on Hainan Island and discuss their mag-matic 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 εHf(t)values of-2.6 to 2.3 corresponding to Hf crustal model ages,ranging from 0.79 Ga to 1.03 Ga,and δ18O values ranging from 6.9‰ to 7.7‰.Zircons from 100-95 Ma granites have εHf(t)values of-4.2 to 1.1 corresponding to Hf crustal model ages of 1.08 Ga to 1.42 Ga,and δ18O values ranging from 6.7‰ to 8.4‰.Increasing εHf(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 evolu-tion.The εNd(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 pro-duced 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 arcs in the Circum-Pacific orogenic belts and identical to those of nearly coeval granitoid intrusions in the continental fragments within the South China Sea basin.We interpret these Cretaceous granitoids in the Peri-South China Sea region as the remnants of a once contiguous Late Mesozoic magmatic arc system that bounded the southern margin of the entire continental Southeast Asia.Our findings do not support the existence of an episode of magmatic quies-cence in the geological record of SE China during the Aptian.
Ⅰ-type granitesCretaceousHainan IslandSoutheast ChinaMagmatic arcperi-South China Sea region
Xiao-Yan Jiang、Yildirim Dilek、Xian-Hua Li
展开 >
State Key Laboratory of Ore Deposit Geochemistry,Institute of Geochemistry,Chinese Academy of Sciences,Guiyang 550081,China
State Key Laboratory of Lithospheric Evolution,Institute of Geology and Geophysics,Chinese Academy of Sciences,Beijing 100029,China
Department of Geology and Environmental Earth Science,Miami University,Oxford,OH 45056,USA
NETL
NSTL
万方数据
