Rare earth elements and yttrium (REY) variability with water depth in hydrogenetic ferromanganese crusts
Rare earth elements and yttrium (REY) variability with water depth in hydrogenetic ferromanganese crusts
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DOI：
10.1016/j.chemgeo.2018.05.045
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发表时间：
2018-08
期刊：
影响因子：
3.9
通讯作者：
K. Azami;N. Hirano;S. Machida;K. Yasukawa;Y. Kato
中科院分区：
文献类型：
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作者：
K. Azami;N. Hirano;S. Machida;K. Yasukawa;Y. Kato
以前曾使用水深小于4公里的样品研究过海水中形成的铁锰结壳的起源和这些结壳中的元素分配。在这里，我们报告的Fe-Mn结壳采样在太平洋内的小斑点火山在水深5.2-6.0公里的地球化学分析。铁锰结壳Mn/Fe比值低（0.63-1.5），Co、Ni、稀土元素和Y（REY）含量高，Ce正异常，表明其为水成成因。铁锰结壳的特点是较低的页岩标准化的La/Pr比值（LaSN/PrSN）比典型的水成铁锰结壳从太平洋。尽管LaSN/PrSN和NdSN/SmSN与水深呈负相关，EuSN/GdSN和DySN/HoSN与水深呈正相关，但REY的分布系数是恒定的。这表明在这些水成铁锰结壳中观测到的REY随水深的变化反映了海水的REY变化。特别是，LaSN/PrSN和水深之间的强相关性有可能用作（古）海洋水文气压计。铁锰结壳稀土元素组成的变化应根据各水深计算的分配系数加以解释。
The origins of ferromanganese (Fe–Mn) crusts that form in seawater and elemental partitioning into these crusts have previously been studied using samples from water depths shallower than 4 km. Here we report geochemical analyses of Fe–Mn crusts sampled from petit-spot volcanoes within the Pacific Ocean at water depths of 5.2–6.0 km. The Fe–Mn crusts have low Mn/Fe ratios (0.63–1.5), high contents of Co, Ni, and rare earth elements and Y (REY), and positive Ce anomalies, indicating a hydrogenetic origin. The Fe–Mn crusts are characterized by lower shale-normalized La/Pr ratios (LaSN/PrSN) than typical hydrogenetic Fe–Mn crusts from the Pacific Ocean. Despite negative LaSN/PrSNand NdSN/SmSNand positive EuSN/GdSNand DySN/HoSNcorrelations with water depth, the distribution coefficients of the REY are constant. This indicates that the observed REY variability with water depth in these hydrogenetic Fe–Mn crusts reflects that of seawater. In particular, a strong correlation between LaSN/PrSNand water depth has potential for use as a (paleo)ocean hydro-barometer. The variety of REY compositions of Fe–Mn crusts should be interpreted on the basis of distribution coefficients calculated for each water depth.