Abstract Rare earth element and yttrium (REY)-rich mud around Minamitorishima Island, Japan, in the western North Pacific Ocean has received significant attention as a novel REY resource. In REY-rich muds, industrially critical metals such as Co, Ni, and Mo occur in relatively high concentrations. We show that Fe-Mn micronodules separated from REY-rich muds are significantly enriched in these elements; we measured Co contents of almost 3000 ppm and Ni contents that exceed 39,000 ppm. Through experiments, we demonstrated that reductive chemical leaching can be used to extract major portions (generally >80%) of the metals associated with Fe-Mn (oxyhydr)oxides from REY-rich muds. The Fe-Mn micronodules were of an oxic diagenetic origin. A simple mass balance calculation indicated that the contribution of the Fe-Mn micronodules to the bulk Fe-Mn (oxyhydr)oxides in the sediment can amount to 8%–50% (median: 18%). The other metals associated with Fe-Mn (oxyhydr)oxides seem to be hosted in Mn-microparticles, probably of a hydrogenetic origin. We estimate that the most promising site for REY-rich mud development contains (9.3 ± 0.6) × 102 t, (1.6 ± 0.1) × 103 t, and (2.8 ± 0.2) × 102 t of leachable Co, Ni, and Mo, respectively, in 1 km2 × 0–10 m below seafloor. These amounts account for 0.66 ± 0.04%, 0.061 ± 0.004%, and 0.097 ± 0.007% of present annual global productions of Co, Ni, and Mo, respectively. The feasibility of extracting these metals as co-products during REY-rich mud development depends on the cost-efficiency of the recovery process, which ultimately depends on their market price in the near future.

中文翻译：

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北太平洋西部深海沉积物中 Fe-Mn 微结核的地球化学特征：从富含 REY 的泥浆中提取副产物金属的潜力

摘要 北太平洋西部日本南鸟岛周围富含稀土元素和钇（REY）的泥浆作为一种新型稀土资源受到了广泛关注。在富含 REY 的泥浆中，Co、Ni 和 Mo 等工业关键金属的浓度相对较高。我们表明，从富含 REY 的泥浆中分离出来的 Fe-Mn 微球明显富含这些元素；我们测量了几乎 3000 ppm 的 Co 含量和超过 39,000 ppm 的 Ni 含量。通过实验，我们证明了还原化学浸出可用于从富含 REY 的泥浆中提取大部分（通常 >80%）与 Fe-Mn（羟基）氧化物相关的金属。铁锰微结节是含氧成岩成因。简单的质量平衡计算表明，Fe-Mn 微球对沉积物中大量 Fe-Mn（羟基）氧化物的贡献可达 8%–50%（中值：18%）。与 Fe-Mn（羟基）氧化物相关的其他金属似乎存在于 Mn 微粒中，可能是氢起源的。我们估计富含 REY 的泥浆开发最有希望的地点包含 (9.3 ± 0.6) × 102 t、(1.6 ± 0.1) × 103 t 和 (2.8 ± 0.2) × 102 t 可浸出的 Co、Ni 和 Mo，分别位于海底以下 1 km2 × 0–10 m。这些数量分别占目前全球 Co、Ni 和 Mo 年产量的 0.66 ± 0.04%、0.061 ± 0.004% 和 0.097 ± 0.007%。在富含 REY 的泥浆开发过程中提取这些金属作为副产品的可行性取决于回收过程的成本效益，