(Tables 1-2, page 195) Chemical composition of ferromanganese crusts and associated smectites from the Gulf of Aden

Fragments of a hydrothermal deposit, partly moulded on pieces of basalt lava, were dredged from the edge of the median valley in the centre of the Gulf of Aden. The deposit consists of two main components, manganese oxide in the form of spongy brown to hard black lumps and coatings, and friable green massive smectite. There are smaller amounts of an iron-oxide component, and mixed manganese-oxide-smectite material. Contents of the less mobile trace elements in the smectite are too low for it to have formed by alteration of basalt glass, and it is interpreted as a direct precipitate from hydrothermal solution. None of the components is enriched in Cu or Zn, or contains appreciable amounts of sulphur. If there are sulphides in this deposit, they must lie beneath the parts sampled.

科研人员从亚丁湾中部中央谷地的边缘拖网采得部分依附于玄武岩熔岩块的热液矿床（hydrothermal deposit）碎块。该矿床包含两类主要组分：一类为呈海绵状棕褐色至坚硬黑色团块与包膜的氧化锰，另一类为易碎的绿色块状蒙脱石（smectite）；此外还含有少量氧化铁组分以及混合氧化锰-蒙脱石物质。蒙脱石中迁移性较弱的微量元素含量过低，不足以通过玄武岩玻璃的蚀变作用形成，因此推断其为热液溶液直接沉淀的产物。该矿床的所有组分均未富集铜（Cu）或锌（Zn），也未检出可观的硫（S）含量。若该矿床中存在硫化物，则其必然位于本次采样区域的下方。