板内玄武岩来源于再循环碳酸盐化榴辉岩的地球化学证据:以四子王旗新生代玄武岩为例  

Geochemical evidence for the generation of intraplate basalts from a carbonated eclogite source:A case study from Cenozoic Siziwangqi basalts

作　　者：吴亚东 杨进辉[1,2] 朱昱升 WU YaDong;YANG JinHui;ZHU YuSheng(State Key Laboratory of Lithospheric Evolution,Institute of Geology and Geophysics,Chinese Academy of Sciences,Beijing 100029,China;College of Earth and Planetary Sciences,University of Chinese Academy of Sciences,Beijing 100049,China;Key Laboratory of Mineral Resources,Institute of Geology and Geophysics,Chinese Academy of Sciences,Beijing 100029,China)

机构地区：[1]中国科学院地质与地球物理研究所,岩石圈演化国家重点实验室,北京100029 [2]中国科学院大学地球与行星科学学院,北京100049 [3]中国科学院地质与地球物理研究所矿产资源研究院重点实验室,北京100029

出　　处：《岩石学报》2023年第9期2583-2597,共15页Acta Petrologica Sinica

基　　金：国家自然科学基金项目(42288201)资助.

摘　　要：本文对中国东部中新世四子王旗玄武岩开展了详细的全岩和橄榄石主、微量元素及全岩Sr-Nd-Pb-Hf-Mg同位素研究,据此探讨它们的成因及源区性质。研究发现,四子王旗玄武岩具有类似于高μ(HIMU)型地幔起源熔体的微量元素分布特征,Zr、Hf、Ti的负异常,高的Zr/Hf比值(Zr/Hf=49.3~54.8),以及低于正常地幔范围的δ26 Mg值(-0.51‰~-0.49‰),表明其来源于碳酸盐化地幔源区。它们还具有低的Sc含量(10.1×10^(-6)~10.5×10^(-6))和高的Gd/Yb比值(8.7~9.4),结合它们橄榄石斑晶低的Fo值,高的NiO含量和Fe/Mn比值,揭示其母岩浆为碳酸盐化榴辉岩部分熔融产生。四子王旗玄武岩具有亏损的Sr-Nd-Hf同位素(87 Sr/86 Sr=0.70370~0.70449;εNd=+6.3~+6.4;εHf=+9.7~+10.3),以及较低的Pb同位素组成(206 Pb/204 Pb=17.94,207 Pb/204 Pb=15.44,208 Pb/204 Pb=37.89),指示它们源区为年轻的再循环洋壳物质,很有可能来自于滞留的西太平洋板片。四子王旗玄武岩位于南北重力梯度带以西并远离海沟,意味着滞留的西太平洋板片在物质上对上覆地幔的影响范围较之前认识的要更广。A detailed study of whole rock and olivine major and trace element and whole rock Sr-Nd-Pb-Hf-Mg isotopic compositions was conducted for the Miocene Siziwangqi basalts in eastern China,to investigate their petrogenesis and the nature of the source.The Siziwangqi basalts exhibit HIMU-like trace element pattern,negative anomalies in Zr,Hf,and Ti,high Zr/Hf ratios(Zr/Hf=49.3~54.8),andδ26 Mg values(δ26 Mg=-0.51‰~-0.49‰)lower than that of normal mantle range,indicating their derivation from a carbonated mantle source.They have low Sc contents(10.1×10^(-6)~10.5×10^(-6))and high Gd/Yb ratios(8.7~9.4).These characteristics,combined with the low Fo,and high NiO and Fe/Mn of olivine phenocrysts,indicate that the primary melt of the Siziwangqi basalts was generated by the partial melting of carbonated eclogite.The Siziwangqi basalts have depleted Sr-Nd-Hf isotopic compositions(87 Sr/86 Sr=0.70370~0.70449;εNd=+6.3~+6.4;εHf=+9.7~+10.3)and relative low Pb isotopic compositions(206 Pb/204 Pb=17.94,207 Pb/204 Pb=15.44,208 Pb/204 Pb=37.89),suggesting a young recycled oceanic material in the source that is most likely from the stagnant western Pacific slab.The Siziwangqi basalts are situated to the west of the North-South Gravity Lineament and far from the trench,which implies that the material influence of the stagnant western Pacific slab on the overlying mantle is broader than previously recognized.

关 键 词：中国东部 新生代玄武岩 碳酸盐化榴辉岩 西太平洋板片 

分 类 号：P588.145[天文地球—岩石学] P597.2[天文地球—地质学]