闽北晚中生代大源高、低ω(Sr)/ω(Y)值花岗岩成因及意义  

Genesis and Implication of the Late Mesozoic Dayuan High and Lowω(Sr)/ω(Y)Granitoids in Northern Fujian,South China

作　　者：王凯兴[1,2] 赵子翔 黄卉 WANG Kaixing;ZHAO Zixiang;HUANG Hui(State Key Laboratory of Nuclear Resources and Environment,East China University of Technology,Nanchang 330013,China;School of Earth Science,East China University of Technology,Nanchang 330013,China)

机构地区：[1]东华理工大学核资源与环境国家重点实验室,江西南昌330013 [2]东华理工大学地球科学学院,江西南昌330013

出　　处：《东华理工大学学报（自然科学版）》2024年第3期201-227,共27页Journal of East China University of Technology(Natural Science)

基　　金：国家自然科学基金项目(41602071);中国核工业集团高校科研攻关项目(201619)。

摘　　要：为探讨闽北晚中生代大源岩体源区物质组成,以及成岩物理化学条件对花岗岩地球化学特征的控制,开展了锆石U Pb同位素年代学、锆石微量元素及Hf同位素、全岩元素和同位素地球化学等研究。结果表明,大源岩体为多期多阶段花岗岩,包括侏罗纪和白垩纪花岗岩,两个时代的花岗岩显示了截然不同的地球化学特征。侏罗纪((160±3)~(166±3)Ma)花岗岩具有Sr含量高和Y含量低,以及ω(Sr)/ω(Y)值高的特征,显示埃达克质岩石特征;其锆石εHf(t)值为-40.69~-11.32,Hf同位素二阶段模式年龄(T DM2(Hf))为1.84~3.83 Ga;全岩(ω(87 Sr)/ω(86 Sr))i为0.71366~0.71814,εNd(t)值为-16.7~-13.5,Nd同位素二阶段模式年龄(T DM2(Nd))为2.05~2.31 Ga。白垩纪花岗岩((143±3)Ma)具有Sr含量低和Y含量高,以及ω(Sr)/ω(Y)值低的特征;其锆石εHf(t)和T DM2(Hf)分别为-15.03~-11.60和2.04~2.34 Ga,(ω(87 Sr)/ω(86 Sr))i为0.70947~0.71343,εNd(t)值为-13.90~-9.78,T DM2(Nd)为1.74~2.05 Ga。元素和同位素地球化学特征表明,大源侏罗纪和白垩纪花岗岩主要来源于地壳物质部分熔融产生的岩浆。侏罗纪花岗岩ω(Sr)/ω(Y)值高可能是由镁铁质岩石在较低的地壳压力、较高的氧逸度和水含量环境下部分熔融所致;白垩纪花岗岩ω(Sr)/ω(Y)值低可能是与变质杂砂岩在较低压力、低氧逸度和水含量环境下部分熔融所致。结合本研究和前人的研究成果,表明华南晚中生代岩浆活动可能与古太平洋板块的西北俯冲有关。To investigate the geochemical composition of the Late Mesozoic Dayuan granitic plutons in northern Fujian 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 highω(Sr)/ω(Y)ratios,displaying characteristics of adakitic rocks.Their zirconεHf(t)values range from-40.69 to-11.32,with Hf isotopic two-stage model ages(T DM2(Hf))ranging from 1.84 to 3.83 Ga;whole-rock(ω(87 Sr)/ω(86 Sr))i ranges from 0.71366 to 0.71814,εNd(t)values from-16.7 to-13.5,and Nd isotopic two-stage model ages(T DM2(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 zirconεHf(t)and T DM2(Hf)range from-15.03 to-11.60 and 2.04 to 2.34 Ga respectively,(ω(87 Sr)/ω(86 Sr))i ranges from 0.70947 to 0.71343,εNd(t)values from-13.90 to-9.78,and T DM2(Nd)from 1.74 to 2.05 Ga.Elemental and isotopic geochemical characteristics suggest that Jurassic and Cretaceous granites in the Dayuan pluton are primarily derived from partial melting of crustal materials.Jurassic granites with highω(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 lowω(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 Paleo-Pacific plate.

关 键 词：地质年代学 花岗岩成因 晚中生代 华南 

分 类 号：P619.14[天文地球—矿床学]