摘要
本文对地矿部“海洋四号”科学考察船１９８７—１９８９年在东赤道太平洋ＣＣ区所取得的２７个深海表层沉积物样品进行Ｕ的地球化学分析，探讨了Ｕ在深海沉积中的地球化学行为。结果表明，不同类型沉积物的Ｕ含量不同，平均值由大至小的次序为含沸石粘土（２．１６×１０￣（－６））、硅质粘土（１．９５×１０￣（－６）），硅质软泥（１．６５×１０￣（－６））、钙质硅质粘土（１．５９×１０￣（－６）），在同类型沉积物中Ｕ的分散性较大；Ｕ在区域上的分布趋势与Ｃｏｒｇ类似而与ＣａＣＯ＿３相反，呈现出由南向北降低的趋势。与大陆边缘海、封闭、半封闭海的沉积物相比，深海沉积物的Ｕ含量最低，表现出Ｕ的亏损；Ｕ的晶体化学性质以及沉积物的物质来源决定了深海沉积物的Ｕ来源于海水和陆地，海水来源的Ｕ被自生粘土矿物和有机质吸附，陆源Ｕ与陆源粘土矿物有关，而较高的Ｅｈ和较低的Ｃｏｒｇ以及生物碎屑组份ＳｉＯ＿２、ＣａＣＯ＿３和Ｐ＿２Ｏ＿５对它起稀释作用都导致Ｕ的亏损，同时，Ｕ和Ｔｈ较大程度的分异也是深海沉积物的主要标志。
deep-sea sediment samples were collected in CC area by R/V“Haiyang Ⅳ” in northern East Pacific Ocean during 1987-1989.U contents in samples are detected by INNA method Based on the smear slide detection,the sediments are divided into four types:zeolitic clay siliceous clay,siliceous ooze and calcareous siliceous clay. U contents are different in these sediment types and are,on the arerage,2.16×10￣(-6) in zeolitic clay,1.95×10￣(-6) in siliceous clay,1.65×10￣(-6) in siliceous ooze and 1.59×10￣(-6) in calcareous-siliceous clay.In the same type of sediments,U has a higher variation coefficient than any other elements,indicating that U is dispersive in deep-sea sediments. The tendency of regional distribution is that U is higher in content in the northern part than in the south, which is similar to Corg and opposite to CaCO_3.Compared with sediments from shelf and enclosed or semi-enclosed sea, deep-sea sediments have the lowest U contents. This fact shows U is in depletion in deep sediments. It is the feature of crystal chemistry of U,Th and the sources of deep-sea sediments that decides the U in deep-sea sediments to have two main sources:sea water and continent.Authigenic clay minerals such assmectite and organic materials absorb U from sea water while terrigenous clay mineralskeep U from land. High Eh and lower Corg and components associated with biogenicfragments as SiO_2,CaCO_3 and P_2O_5 all dilute U contents and make U depleted.Anotherimportant feature is that Th/U ratios are high in deep-sea sediments,which reflects astrong differentiation in CC area.
出处
《海洋地质与第四纪地质》
CAS
CSCD
北大核心
1996年第1期59-67,共9页
Marine Geology & Quaternary Geology
基金
国家自然科学基金
关键词
东太平洋
沉积物
U地球化学
uranium geochemistry sediments East Pacific Ocean
