Abstract Nickel isotopes are a novel and promising tracer of the chemistry of past ocean environments, but realisation of this tracer's potential requires a comprehensive understanding of the controls on Ni burial in the marine sedimentary archive. An outstanding puzzle in the marine budget of Ni, first recognised in the 1970s, is a major imbalance in the known inputs and outputs to and from the ocean: the sedimentary outputs of Ni are much larger than the inputs (rivers, dust). Much more recently, it has also been recognised that the outputs are also considerably isotopically heavier than the inputs. In this study, we find light Ni isotope compositions ( δ 60 NiNIST SRM986 = −0.2 to −0.8‰) for Mn-rich sediments from the eastern Pacific compared to Fe-Mn crusts (at about +1.6‰). These data suggest that diagenetic remobilisation of isotopically heavy Ni leads to a significant benthic Ni flux (estimated at 0.6 − 2.3 × 10 8 mol/yr), similar in magnitude to the riverine flux, to the ocean. Diagenetic remobilisation of Ni may occur either via cycles of Mn-oxide dissolution and precipitation, with associated Ni sorption and release, or during mineralogical transformation of birnessite to todorokite. A minor role for retention of isotopically light Ni by Fe oxides or Fe-rich authigenic clays is also proposed. Overall, a benthic flux of isotopically heavy Ni (at about +3‰) can balance the marine Ni budget, pinpointing diagenesis as a key missing piece of the Ni puzzle.

中文翻译：

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平衡海洋镍预算

摘要 镍同位素是一种新的、有前途的海洋环境化学示踪剂，但要实现这种示踪剂的潜力，需要全面了解对海洋沉积档案中镍埋藏的控制。在 1970 年代首次认识到镍的海洋预算中的一个突出难题是已知的进出海洋的输入和输出的严重不平衡：Ni 的沉积输出远大于输入（河流、灰尘）。最近，人们还认识到输出的同位素比输入重得多。在这项研究中，我们发现东太平洋富锰沉积物的轻 Ni 同位素组成（δ 60 NiNIST SRM986 = -0.2 至 -0.8‰）与 Fe-Mn 结壳（约 +1.6‰）相比。这些数据表明，同位素重 Ni 的成岩再迁移导致了显着的底栖 Ni 通量（估计为 0.6 - 2.3 × 10 8 mol/yr），其量级与河流通量相似，到海洋。Ni 的成岩再动员可能通过 Mn 氧化物溶解和沉淀的循环以及相关的 Ni 吸附和释放发生，或者在水钠锰矿到 todorokite 的矿物学转变过程中发生。还提出了铁氧化物或富铁自生粘土保留同位素轻镍的次要作用。总体而言，同位素重镍的底栖通量（约 +3‰）可以平衡海洋镍收支，将成岩作用确定为镍难题的关键缺失部分。Ni 的成岩再动员可能通过 Mn 氧化物溶解和沉淀的循环以及相关的 Ni 吸附和释放发生，或者在水钠锰矿到 todorokite 的矿物学转变过程中发生。还提出了铁氧化物或富铁自生粘土保留同位素轻镍的次要作用。总体而言，同位素重镍的底栖通量（约 +3‰）可以平衡海洋镍收支，将成岩作用确定为镍难题的关键缺失部分。Ni 的成岩再动员可能通过 Mn 氧化物溶解和沉淀的循环以及相关的 Ni 吸附和释放发生，或者在水钠锰矿到 todorokite 的矿物学转变过程中发生。还提出了铁氧化物或富铁自生粘土保留同位素轻镍的次要作用。总体而言，同位素重镍的底栖通量（约 +3‰）可以平衡海洋镍预算，将成岩作用确定为镍难题的关键缺失部分。