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

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.