东太平洋多金属结核U、Th同位素深度分布特征与生长速率  

Depth Distribution Features of U、Th Isotopes and Growth Rates of Polymetallic Nodules in Eastern Pacific

作　　者：蔡毅华[1] 黄奕普[1] 陈敏[1] 刘广山[1] 邱雨生[1] 

机构地区：[1]厦门大学海洋学系,福建厦门361005

出　　处：《厦门大学学报（自然科学版）》2000年第5期657-663,共7页Journal of Xiamen University：Natural Science

基　　金：中国大洋矿产资源研究开发协会"九五"国家专项资助项目!(DY95- 0 2 - 15)

摘　　要：:研究了东太平洋多金属结核中 U、Th同位素的深度分布与生长速率 .结果表明 ,东太平洋多金属结核中的 2 3 4U/ 2 3 8U) A.R.与海水接近 ,证实了 U的海水来源 ;2 3 4U及 2 3 8U的活度并不随深度增加而减小 ,而是在次表层和更深层出现极大值 .2 36 7站结核中 2 3 2 Th的活度在次表层有最大值 ,之后随深度的增加而降低 ,反映了结核生长过程中成岩作用的影响 ;1797站南结核中 2 3 2 Th表层有最大值 ,其它各层的变化较小 ,说明成岩作用对它的影响较小 .结核中存在大量过剩的 2 3 0 Th,并随深度呈指数衰减 ,根据 2 3 0 Thex法及 2 3 0 Thex/ 2 3 2 Th法求出东太平洋多金属结核的生长速率为 5.6 4～ 7.12 m m/Ma.The uranium and thorium isotopes' distribution features and growth rates of polymetallic nodules in Eastern Pacific were studied. The results showed that uranium in nodules comes from seawater because its 234 U/ 238 U) A.R. is similar with that of seawater. The specific activities of 234 U, 238 U show maximum in the subsurface and the deeper layer rather than decrease with the depth. 232 Th in nodule 2367 displays the maximum at subsurface and then decreases with the depth, indicating of the influence of the diagenesis during nodule growth. In contrast, 232 Th in nodule 1797 display maximum at surface and is nearly constant with depth, which suggest the less influence of diagensis than nodule 2367. 230 Th, which is much more excess than its parent, 234 U, decrease exponentially with depth in nodules. Based on the 230 Th ex and 230 Th ex / 232 Th methods, the growth rates of studied nodules are from 5.64 to 7.12 mm/Ma.

关 键 词：太平洋 多金属结核 生长速率 铀同位素 钍同位素 

分 类 号：P736[天文地球—海洋地质]