熔体包裹体揭示山东昌乐玄武岩源区不均一及其意义  

Melt inclusions reveal heterogeneity in mantle source of Changle basalts,Shandong Province and its implications

作　　者：莫霏 张银慧 洪路兵 刘希军 张乐[2] 贺鹏丽[2] MO Fei;ZHANG Yinhui;HONG Lubing;LIU Xijun;ZHANG Le;HE Pengli(Guangxi Key Laboratory of Exploration for Hidden Metallic Ore Deposits/Collaborative Innovation Center for Exploration of Nonferrous Metal Deposits and Efficient Utilization of Resource,School of Earth Sciences,Guilin University of Technology,Guilin 541006,Guangxi,China;State Key Laboratory of Isotope Geochemistry,Guangzhou Institute of Geochemistry,Chinese Academy of Sciences,Guangzhou 510640,Guangdong,China)

机构地区：[1]桂林理工大学地球科学学院广西隐伏金属矿产勘查重点实验室/有色金属矿产勘查与资源高效利用省部共建协同创新中心,广西桂林541006 [2]中国科学院广州地球化学研究所,同位素地球化学国家重点实验室,广东广州510640

出　　处：《地球化学》2024年第6期870-885,共16页Geochimica

基　　金：广西科技基地和人才专项(桂科AD22035160);广西战略性关键矿产资源成矿与勘查科技创新基地建设项目(桂科ZY21195031);国家自然科学基金项目(42172053、42002057);广西八桂学者项目(2018-有色金属成矿理论与勘查技术)联合资助。

摘　　要：中国东部新生代强、弱碱性玄武岩分别显示年轻HIMU-和EM-OIB的化学组成特征。然而,它们的成分差异,究竟是与源区组成有关,还是受控于熔融过程,至今仍有争议。为此,本研究分析了山东昌乐玄武岩的熔体包裹体的主量、微量元素和Pb同位素组成。结果显示,熔体包裹体的SiO_(2)、全碱以及微量元素配分模式均与弱碱性玄武岩相似,但它们的微量元素比值(Rb/Nb、Ba/La、Nb/La、Ba/Nb和Nd/Pb)和Pb同位素组成变化大,显示弱碱性玄武岩与强碱性玄武岩的混合特征。由于昌乐熔体包裹体主要经历了橄榄石结晶分异且无明显地壳混染,它们的成分变化反映了地幔源区成分的高度不均一,暗示强、弱碱性玄武岩可能起源于相似源区,两者的成分差异可能是选择性熔融引起的。The Cenozoic strongly and weakly alkaline basalts in Eastern China exhibit the geochemical features of young HIMU-and EM-OIB,respectively.However,whether this discrepancy is attributable to compositional components in the mantle source or melting processes remains controversial.To address this issue,this study reported the major and trace element and Pb isotopic compositions of melt inclusions in the Changle basalts,Shandong province.Our results showed that the melt inclusions had SiO_(2)and total alkali contents,as well as trace element compositions,similar to those of weak alkaline basalts in this region,but their trace element ratios(Rb/Nb,Ba/La,Nb/La,Ba/Nb and Nd/Pb)and Pb isotopic compositions were highly variable,ranging from weakly to strongly alkaline basalts.Because the Changle melt inclusions experienced olivine-dominant fractionation without obvious crustal contamination,their compositional variations indicate highly compositional heterogeneity in the mantle source,and the comparable compositions of the mantle sources of strongly and weakly alkaline basalts are inferred,therefore highlighting the critical role of differential melting processes in the compositional variations of the Cenozoic basalts in Eastern China.

关 键 词：中国东部 新生代玄武岩 熔体包裹体 昌乐 选择性熔融 源区组成不均一 

分 类 号：P595[天文地球—地球化学] P581[天文地球—地质学] P588.145