87Sr/86Sr Isotopic Ratio of Ferromanganese Crusts as a Record of Detrital Influx to the Western North Pacific Ocean

Keishiro Azami*, Naoto Hirano, Jun Ichi Kimura, Qing Chang, Hirochika Sumino, Shiki Machida, Kazutaka Yasukawa, Yasuhiro Kato

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review


In this study, the Sr isotope ratios (IRs; 87Sr/86Sr) of ferromanganese (Fe–Mn) crusts are analyzed through laser ablation inductively coupled plasma multiple-collector mass spectrometry. A sample collected from off Minamitorishima Island showed uniform Sr IRs (0.70906–0.70927) similar to that of present-day seawater with more than 36 mm thickness. Meanwhile, a detritus-rich sample collected from off northeast (NE) Japan showed a wide variation in Sr IRs (0.707761–0.709963). The Sr IR variation in the Fe–Mn crust from off NE Japan suggests detrital influx contributions from both the NE Japan arc (<0.708) and aeolian dust from China (>0.718). Detrital flux from the NE Japan arc increases from the bottom to middle layers, possibly due to the uplift of the Ou backbone range that occurred after ~2 Ma. The increased influx of the aeolian dust in the outer layer is attributable to global cooling in the Quaternary that increased the loess dust transportation from China to the western North Pacific Ocean. Meanwhile, the influence of the detrital influx on the sample from off Minamitorishima Island appeared to be negligible. The Sr IR analysis with high spatial resolution proposed in this study possibly improves the burial history of Fe–Mn nodules.

Original languageEnglish
Article number943
Issue number8
Publication statusPublished - 2022 Aug
Externally publishedYes


  • ferromanganese crust
  • ferromanganese nodule
  • paleoceanography
  • Sr isotope ratio
  • western North Pacific

ASJC Scopus subject areas

  • Geotechnical Engineering and Engineering Geology
  • Geology


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