IntroductionCobalt is the most important critical element in ferromanganese crusts. Co concentration in the Fe-Mn crusts is one of the key parameters for determination of the Co resource. Thus, it is essential to clarify the controls on the variations of Co concentration of ferromanganese crusts.MethodsTo clarify the controls on Co concentration of hydrogenetic nonphosphatized ferromanganese crusts, an equation was deduced based on Fick’s First Law: Co(%)=Mn02(%)·Dsw·cswδ·zGR·Ssp, and eight potential controls were gleaned from this equation, including dilution, diffusivity of Co ions in seawater (Dsw), temperature which controls the Dsw, Co ion concentration in seawater (Csw), the diffusion distance of Co ions near the interface of seawater and Fe-Mn crusts (δ), thickness of one molecular layer (z), growth rate (GR), and specific surface area of Fe-Mn crusts (Ssp). To constrain the value of Co ion diffusion gradients (Csw¯/δ) and consequently verify the proposed equation, we determined the Co concentrations, growth rates, and specific surface area of the outermost layer of Fe-Mn crusts, and calculated diffusivity of Co2+.ResultsThe Csw¯/δ for the Fe-Mn crusts from Caiwei seamount (Magellan seamounts) was determined to be 295-496 pM/mm, which are reasonable for the Co ion concentrations and seawater mixing in the deep ocean.DiscussionAccording to the equation established in this study, the trend of decreasing Co concentrations in Fe-Mn crusts with increasing water depth is controlled mainly by dilution and to a lesser extent by seawater Co ion concentration, temperature of seawater, and consequently the diffusivity of Co ions in seawater.

中文翻译：

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前沿 |西太平洋麦哲伦海山锰铁结壳中钴浓度的控制


简介钴是锰铁结皮中最重要的关键元素。Fe-Mn 结壳中的 Co 浓度是确定 Co 资源的关键参数之一。因此，必须阐明对锰铁结壳 Co 浓度变化的控制。方法为了阐明对水生非磷酸化锰铁结皮 Co 浓度的控制，根据 Fick 第一定律推导方程：Co（%）=Mn02（%）·Dsw·cswδ·zGR·从该方程中收集了 Ssp 和 8 个电位控制因素，包括稀释度、Co 离子在海水中的扩散率 （Dsw）、控制 Dsw 的温度、海水中 Co 离子浓度 （Csw）、Co 离子在海水和 Fe-Mn 结壳界面附近的扩散距离 （δ）、单分子层厚度 （z）、生长速率 （GR） 和 Fe-Mn 结壳的比表面积 （Ssp）。为了约束 Co 离子扩散梯度 （Csw ̄/δ） 的值并因此验证所提出的方程，我们确定了 Fe-Mn 结壳最外层的 Co 浓度、生长速率和比表面积，并计算了 Co2+ 的扩散率。结果麦哲伦海山（Magellan seaamount）对彩尾海山Fe-Mn结壳的Csw ̄/δ为295—496 pM/mm，对于深海中Co离子浓度和海水混合来说是合理的。讨论根据本研究中建立的方程，Fe-Mn 结壳中 Co 浓度随水深增加而降低的趋势主要由稀释控制，其次受海水 Co 离子浓度、海水温度以及 Co 离子在海水中的扩散率控制。