西北太平洋表层沉积物地球化学特征及其物源指示意义

Geochemical characteristics of surface sediments in Northwest Pacific and their indication of material sources

为深入了解西北太平洋表层沉积物地球化学特征及物质来源,对大洋40航次在西北太平洋马尔库斯-威克海山区采集的表层沉积物进行了全岩地球化学和黏土矿物测试分析。结果表明,研究区表层沉积物稀土元素(REE)平均质量分数为302.87×10-6,北美页岩标准化稀土配分模式与黄土相似,并具Ce轻微负异常和Eu无异常特征。稀土配分模式、判别函数(discriminant functions,DF)、M/I(蒙脱石/伊利石)及涂片鉴定等结果指示沉积物物源具有多源性,主要为陆源风尘物质,并受海洋自生物质的强烈影响,海山玄武岩及其蚀变产物和硅质生物也有一定的贡献。研究区沉积物稀土特征既不同于边缘海沉积物,也有别于远洋沉积物,而与弧后盆地沉积物类似。结合1/δCe-LREE/HREE和LREE/HREE-Y/Ho判别图解结果,研究区沉积物物源结构属性应介于边缘海沉积物与远洋沉积物之间,为洋陆过渡区沉积。

For a deep insight of the geochemical characteristics and material origins of surface sediments in Northwest Pacific,the measurements on whole-rock geochemistry and clay minerals were taken on the surface sediments collected during the DY-40 cruise in the Marcus-Wake Seamount of the Northwest Pacific.The results show that the average content of REE is 302.87×10-6,North American shale normalized REE pattern for samples are similar to that of loess with slightly negative Ce and positive Eu anomalies.The results of REE distribution patterns,discriminant functions(DF),M/I(montmorillonite/illite)and smear identification indicate that the samples show multiple material origins and are strongly influenced by the marine biomass,seamount basalts and their alteration products and siliceous organisms also have certain contributions.The REE characteristics of sediments in the study area are different from those of marginal sea sediments and pelagic sediments,similar to sediments in the back-arc basins.Based on the 1/δCe-LREE/HREE and LREE/HREE-Y/Ho discrimination plot,the sedimentary material source structure properties of the study area should be between marginal sea sediments and pelagic sediments,which is an ocean-continent transitional sedimentary property.