九州-帕劳海脊南段铁锰结壳物质组成特征及成因机制

铁锰结壳（又称富钴结壳、多金属结壳）富含Co、Cu、Mn、Ni、Ti、V、REE、Y和Zn等人类日常生活和高新技术产业亟需的关键金属，是一种重要的战略性矿产资源。本文对九州-帕劳海脊南段水深1900～2600 m处获得的9个站位铁锰结壳样品进行了矿物学和地球化学研究，分析了铁锰结壳的矿物组成、主微量元素和稀土元素含量，并进一步探讨了铁锰结壳的成因类型。结果表明，研究区铁锰结壳的矿物组成以水羟锰矿为主，同时含有大量非晶态铁氧/氢氧化物；Mn、Fe、Co、Ni、Cu平均含量分别为16.15%、15.38%、0.32%、0.33%、0.10%；CaO/P2O5均值为5.93，表明九州-帕劳海脊南段铁锰结壳样品均未发生磷酸盐化作用；铁锰结壳明显富集稀土元素（含Y，REYs），平均含量为1194 μg/g，轻稀土显著富集，稀土元素经后太古代澳大利亚页岩（PAAS）标准化后配分模式整体相对平坦，呈现Ce正异常而Eu无异常，与海水呈现镜像关系，说明铁锰结壳稀土元素主要来源于海水。铁锰结壳的矿物组成和元素判别图均表明九州-帕劳海脊南段铁锰结壳属于水成型，未受明显的成岩作用影响。

Composition characteristics and genetic mechanism of ferromanganese crusts in the southern section of the Kyushu-Palau Ridge

Ferromanganese crusts (also known as cobalt-rich crusts or polymetallic crusts) are important strategic resources of minerals rich in key metals (Co, Cu, Mn, Ni, Ti, V, REE, Y, and Zn), which is essential for both human being’s daily life and high-tech industries. We conducted mineralogical and geochemical analyses of nine ferromanganese crust stations obtained from depths of 1900～2600 m in the southern section of the Kyushu-Palau Ridge, analyzed the mineral composition, major and trace element contents, and rare earth element (REE) contents of the ferromanganese crusts, and explored their genetic types. Results show that the mineral composition of the ferromanganese crusts was dominated by vernadite, and contained a large amount of amorphous iron oxide/hydroxide. The average contents of Mn, Fe, Co, Ni, and Cu were 16.15%, 15.38%, 0.32%, 0.33%, and 0.10%, respectively. The average CaO/P2O5 ratio was 5.93, indicating that the ferromanganese crust samples from the southern section of Kyushu-Palau Ridge had not undergone phosphatization. The ferromanganese crusts were significantly enriched in REYs, with an average content of 1194 μg/g. Light REEs were significantly enriched, and the Post-Archean Australian Shales (PAAS) normalized distribution pattern was relatively flat, showing a positive Ce anomaly and no Eu anomaly, and the REEs in the ferromanganese crusts may have originated from seawater. The mineral composition and genetic discrimination diagrams of the ferromanganese crusts indicated that they were of hydrogenetic origin and were not significantly affected by diagenesis.