Manganese nodules were found in the deep-sea core (5826m depth). They were deposited at the depth of 3 meters under the ocean floor. The largest one (3cm in diameter) was studied by the X-ray diffraction method, the differential thermal analysis and the infrared absorption spectroscopy. The chemical compositions (Mn, Fe, SiO
2, Ti) were also analyzed. According to these results, δ-MnO
2 or Birnessite would be contained in the nodule. Distribution patternes of nickel and iron on the cross section of the nodule were studied by the chromatographic contact print method. The growth rate of the nodule was calculated by the fission track method and it was 0.03mm/10
3 years. The origin of nickel was discussed on a few hypothesis.
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