【作者】 戴宝章； 蒋少涌； 赵葵东； 高剑锋；

【Author】 DAI Baozhang JIANG Shaoyong ZHAO Kuidong GAO Jianfeng Department of Earth Science,Nanjing University,State Key Laboratory for Mineral Deposits Research,Nanjing,Jiangsu,210093

【机构】 南京大学地球科学系成矿作用国家重点实验室；

【摘要】 硼及其同位素能够有效地反映由于俯冲板片脱水引起的湿地幔楔部分熔融过程在火山岩中存留的地球化学信息。本次研究中使用同位素稀释法对华南中生代玄武岩进行了硼含量的测定,结合稀土与微量元素分析结果对玄武岩成因及构造背景进行探讨。玄武岩的硼含量主要集中在（1～5）×10^-6,只有几个样品具有较高的含量(最高可达19×10^-6),按时代和空间位置划分出的3组样品在硼含量上没有明显差别。在B/Ce,Nb/Be 的协变图解上,中侏罗世玄武岩表现出OIB 特征。最临近太平洋板块的白垩世东区玄武岩富集LILE,并出现Nb-Ta 亏损,具有岛弧火山岩特征,但硼没有富集。进行系统的B-Li-O 同位素分析能有效地揭示华南中生代玄武岩的形成过程及该区的构造演化。更多还原

【Abstract】 Although not the dominant facies,basalts are quite widely distributed in southeast China,and thus have special significancein studying the tectonic evolution of this region.The dominant eruption ages of basalts are 175±5 Ma and 80～110 Ma.In thisstudy,all basalt samples（31 samples）were divided into three groups:Group I（13 samples）of Middle Jurassic,Group ,IIa（4 sam-pies）of Cretaceous basalts from the western part of southeast China,and Group IIb（14 samples）of Cretaceous basalts from the eas-tern part of southeast China.Samples of Group IIb are rich in LILE and show evident depletion of Nb and Ta in the spider diagramof primary mantle normalized incompatible elements,which is generally thought to be related to hydrated mantle wedge by fluids fromthe subduction slab.In this study,the authors aim to employ boron geochemistry to trace the source of boron in basalts from southeastChina and to assess the contribution of the subduction slab to the basalt generation,in particular the generation of Group IIb basalts.The boron contents of basalt samples were analyzed using the isotope-dilution（ID）ICP-MS method at the State Key Laboratory forMineral Deposits Research,Nanjing University.The results show that,compared with recent basalts,all basalts under study are re-latively poor in boron,being mainly in the range of（1～5）×10^-6,with only a few samples having higher abundances(up to 19.0×10^-6).The boron versus other element plots（e. g.,B/Ce versus Ce） for Group I basahs indicate a clear OIB affinity for MiddleJurassic basalts,which possibly erupted in an intra-continental rift setting without any contributions from subducted slab related to Pa-cific Plate.Further analyses of B-O-Li isotopes for these basalts may provide a better clue to their origin and tectonic settings.更多还原