(Table 2, Page 287) Chemical composition of manganese nodules from GH76-1 cruise

Chemical analyses of manganese nodules from the Central Pacific Basin show that their chemical composition varies regionally, although that of the associated sediments is markedly uniform throughout the basin. Mn content varies from 16 to 32% in average. Its higher value is generally found in nodules from siliceous clay and a few from deep-sea clay. Fe content tends to enrich in nodules from deep-sea clay area. Most manganese nodules, except those from deep-sea clay, are remarkably depleted in Fe compared with ones from the other Pacific regions. Mostly, Cu and Ni contents exceed 1% in nodules from siliceous clay, and decrease towards the northwest of the basin where deep-sea clay is distributed. The inter-element relationship between manganese nodules and associated sediments suggests that the mechanism of incorporation of major and minor elements in nodules is apparently different from that of the associated sediments. This finding seems to provide a new interpretation on the problem why manganese nodules having low accumulation rate are not buried by the associated sediments with greater sedimentation rate and then occur on sediment-seawater interface.对中太平洋盆地（Central Pacific Basin）锰结核（manganese nodules）开展的化学分析结果表明，尽管该盆地内的伴生沉积物（associated sediments）化学组成整体显著均一，但锰结核的化学成分存在区域性差异。锰（Mn）的平均含量介于16%至32%之间。硅质黏土（siliceous clay）环境产出的结核锰含量普遍更高，少数深海黏土（deep-sea clay）中的结核亦呈现这一特征。铁（Fe）含量则在深海黏土区域的结核中更为富集。与太平洋其他区域产出的结核相比，除深海黏土中的结核外，绝大多数锰结核的铁含量显著偏低。硅质黏土环境产出的结核中，铜（Cu）与镍（Ni）的含量大多超过1%，且向分布有深海黏土的盆地西北部逐渐降低。锰结核与其伴生沉积物的元素间关联特征表明，结核中常量元素与微量元素的赋存机制，显然与伴生沉积物的赋存机制截然不同。这一发现似乎为解答“为何堆积速率（accumulation rate）较低的锰结核不会被沉积速率（sedimentation rate）更高的伴生沉积物掩埋，反而留存于沉积物-海水界面（sediment-seawater interface）之上”这一问题提供了新的解释思路。