东菲律宾海深水区新型铁锰结壳的特征和成因

CHARACTERISTICS AND ORIGIN OF THE NEW-TYPE FERROMANGANESE CRUSTS FROM DEEPWATER AREAS OF THE EAST PHILIPPINE SEA

  • 摘要: 对取自东菲律宾海深水区致密-半固结沉积物表层的新型铁锰结壳典型样品进行了X射线衍射、X射线荧光、电感耦合等离子体原子发射光谱及加速器质谱研究。结壳的组成矿物主要有δMnO2、铁的氧化物/氢氧化物、石英、长石和黏土矿物等。与海山结壳相比,其Mn、Co、Ni、Zn、Pb含量均较低,而Fe、Cu、Al含量则相对较高。Mn/Fe值平均仅为0.24,也低于海山结壳Mn/Fe的平均值。相关性分析、元素分配系数分析及稀土元素北美页岩标准化配分模式等结果均表明,研究区结壳为一新型边缘海深水水成结壳,与海山水成结壳间存在一定差异。结壳的物质组分主要来自于同期海水,同时碎屑物质对其形成也有一定贡献;并且它们自形成以来没有遭受明显的成岩后期改造和元素再迁移,具有较高的古海洋学应用价值。

     

    Abstract: XRD, XRF, ICP-OES and ICP-MS analyses were carried out on typical new-type ferromanganese crusts sampled on the surface of compact to half-solid sediment from deepwater areas of the East Philippine Sea. The crusts are mainly composed of δMnO2, FeOOH·nH2O, quartz, feldspar, clay minerals and so on. Compared to seamount crusts, their Mn, Co, Ni, Zn and Pb content is lower, whereas the abundance of Fe, Cu and Al is higher. The average of Mn/Fe ratios is only 0.24, which is also lower than that of seamount crusts. Analysis results of interelemental association, elemental distribution coefficient and REE NASC-normalized pattern all indicate that the studied crusts are new-type deepwater ferromanganese crusts in the margin sea, which are somewhat different from seamount crusts. Sources of new-type crusts mainly come from homochronous seawater and the detrital materials also make some contribution. Having not been influenced by significant post-depositional reconstruction and remobilization of elements, the new-type crusts have important paleoceanographic application value.

     

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