Genesis and Implication of the Late Mesozoic Dayuan High and Low ω(Sr)/ω(Y)Granitoids in Northern Fujian,South China
To investigate the geochemical composition of the Late Mesozoic Dayuan granitic plutons in northern Fu-jian province and the control of physico-chemical conditions on the granites,zircon U-Pb isotopic dating,zircon trace elements and Hf isotopes,whole-rock elements,and isotopic geochemical compositions were conducted.The study indicates that the Dayuan granitic pluton consists of multi-stage and multi-period granites,including Jurassic and Cretaceous granites,which exhibit markedly different geochemical characteristics.The Jurassic granites((160±3)to(166±3)Ma)have high Sr contents,low Y contents,and relatively high ω(Sr)/ω(Y)ratios,dis-playing characteristics of adakitic rocks.Their zircon εHf(t)values range from-40.69 to-11.32,with Hf isotop-ic two-stage model ages(TDM2(Hf))ranging from 1.84 to 3.83 Ga;whole-rock(ω(87Sr)/ω(86Sr))i ranges from 0.713 66 to 0.718 14,εNd(t)values from-16.7 to-13.5,and Nd isotopic two-stage model ages(TDM2(Nd))from 2.05 to 2.31 Ga.The Cretaceous granites((143±3)Ma)have low Sr contents,high Y contents,and lowω(Sr)/ω(Y)ratios;their zircon εHf(t)and TDM2(Hf)range from-15.03 to-11.60 and 2.04 to 2.34 Ga re-spectively,(ω(87Sr)/ω(86Sr))i ranges from 0.709 47 to 0.713 43,εNd(t)values from-13.90 to-9.78,and TDM2(Nd)from 1.74 to 2.05 Ga.Elemental and isotopic geochemical characteristics suggest that Jurassic and Creta-ceous granites in the Dayuan pluton are primarily derived from partial melting of crustal materials.Jurassic granites with high ω(Sr)/ω(Y)ratios may have formed by partial melting of mafic rocks under lower crustal pressure,high oxygen fugacity,and high water content.Cretaceous granites with low ω(Sr)/ω(Y)ratios may be related to partial melting of metasandstones under low pressure,low oxygen fugacity,and water content.Combined with previous studies,the Late Mesozoic magmatic activities in South China may be related to the northwest subduction of the Pa-leo-Pacific plate.
geochronologygenesis of graniteLate MesozoicSouth China
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维普
