南鸟岛东南部海域沉积物地球化学特征及其稀土资源指示意义

Geochemical Characteristics of Sediments in Southeast Sea Area of Minamitorishima Island and Their Indication of Rare Earth Elements Resources

为了深入了解南鸟岛东南部海域表层沉积物的物质来源及其沉积环境和稀土元素富集情况,对大洋40航次在该区获取的深海沉积物岩心进行了主量、微量以及稀土元素含量测试分析。结果表明:沉积物为典型的深海黏土沉积。稀土元素标准化配分模式及La/Yb、La/Tb等结果表明,研究区沉积物物源受陆源物质主导,同时海山玄武岩及其风化产物与硅质沉积也有一定的贡献;结合δCe值与微量元素相关比值分析,研究区总体为稳定的偏氧化环境;区域内稀土元素富集主要受生物磷酸盐控制,并同时受到铁锰氧化物的影响;受陆源物质沉积作用的广泛影响,区域内表层沉积物中稀土元素质量分数偏低,但随深度增加,稀土元素富集程度规律性渐次升高。根据CaO/P2O5-w(ΣREY)相关性非线性拟合,推测在710 cm以下深度可能有富稀土元素深海沉积物的分布。

For a deep insight of the material origins,sedimentary environment and REE enrichment of sediment in southeastern sea area of Minamitorishima Island,this study takes the measurements on major,trace and rare earth elements(REE)of deep sea sediments core gained during the DY-40 Cruise.The results show that the sample is a sort of typical pelagic clay.The North American shale normalized REE pattern and the results of La/Yb and La/Tb indicate that the sediments in the study area are dominated by the terrestrial sources,seamount basalts and their weathering products and siliceous sediments also make certain contributions.According toδCe value and trace element-related ratio,we suggest the study area is generally a stable oxidized environment.The enrichment of rare earth elements in the region is mainly controlled by bio-phosphate,and also affected by iron-manganese oxide.Affected by the deposition of terrigenous materials,the content of REE of surface sediments is low,but with the increase of depth,the regularity of rare earth enrichment gradually increases.According to the nonlinear fitting of CaO/P2O5 andΣREY,we speculate that there may be a distribution of REE rich deep sea sediments below 710 cm.