古海洋环境演化对富钴结壳稀土元素富集的制约

Constraints of Paleoceanographic Environmental Evolution on REEs Enrichment in Co-Rich Crust

为了探讨古海洋环境演化对海山富钴结壳稀土元素富集的制约,本次选取西太平洋Lamont海山具有多层结构富钴结壳L1作为研究对象,逐层取样分析研究,认为古海洋环境演化以及磷酸盐化作用对不同稀土元素的影响不同:Ce含量受海洋生产力水平的制约,与形成时古海洋生产力水平呈正相关关系,但受磷酸盐化影响并不显著;而磷酸盐化对富钴结壳中其他稀土元素影响存在明显差异:导致老壳层中稀土元素相对较少,而重稀土元素则相对增加。另外富钴结壳壳层在生成后可能仍然继续与周边海水发生稀土元素交换,导致壳层生成得越早,其重稀土元素相对于其他稀土元素越富集,而Eu则越亏损。

In order to investigate the constraints of pa-leoceanographic environmental evolution on the REEs enrichment in Co-rich crust, a Co-rich crust with multilayer structure from Lamont Guyot in the Western Pacific （L1） was selected to analyzed layer-by-layer. This study suggested that the effects of the paleoceanographic environmental evolution and phosphatization on the various REE were different： The Ce content was constrained by the oceanic productivity level, and correlated positively with the paleoceanographic productivity level when the layer formed, and was not affected significantly by the phosphatization. However, the phosphatization constrained the contents of other REEs significantly, and resulted in the depletion of LREEs and enrichment of HREEs relatively. Furthermore, the Co-rich Fe-Mn crusts might exchange REEs with ambient seawater, which might result in the enrichment of HREEs in old crustal generations and depletion of Eu.