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The Distribution of Total Alpha Radioactivity in Selected Manganese Nodules from the North Pacific: Implications for Growth Processes

  • J. D. Macdougall
Part of the Marine Science book series (MR, volume 9)

Abstract

Analyses of the total alpha radioactivity distribution in 31 North Pacific manganese nodules yield an average growth rate of 6.8 (±2) mm/m.y. Samples from a single box core show almost identical total activity vs. depth profiles, regardless of nodule size or shape. A characteristic feature of many nodules examined is an apparent change (steepening) in slope of the alpha activity profile between depths of 0.5–1.5 mm. This feature may reflect a fundamental feature of nodule growth, possibly mobility of 230Th or its daughters in a regular way, interrupted growth, or nodule turnover. Near-surface decreases in total alpha activity probably result from 226Ra loss.

Keywords

Alpha Particle Alpha Activity Track Density Nodule Surface Manganese Nodule 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

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References

  1. Andersen, M. E. (1978) Accumulation rates of manganese nodules and sediments: An alpha track method. Unpublished M.S. thesis, Univ. Calif. San Diego, 113 p.Google Scholar
  2. Andersen, M.E. and Macdougall, J.D. (1977) Accumulation rates of manganese nodules and sediments: An alpha track method, Geophys. Res. Lett. 4, 351–353.CrossRefGoogle Scholar
  3. Cochran, J. K. and Krishnaswami, S. (1977) U/Th series nuclides in sediment, pore water and manganese nodules of the North Equatorial Pacific, Trans. Am. Geophys. Union 58, 420.CrossRefGoogle Scholar
  4. Greenslate, J. (1977) Manganese concretion wet density: a marine geochemical constant, Marine Mining 1, 125–148.Google Scholar
  5. Heye, D. (1975) Wachstumverhaltnisse von Manganknollen, Geologisches Jahrbuck, Reihe E, Heft 5.Google Scholar
  6. Krishnaswami, S., Cochran, J. K., Turekian, K. K. and Sarin, M. M. (1978) Time scales of deep-sea ferromanganese nodule growth based on 10Be and alpha track distributions and their relation to uranium decay series measurements. Preprint.Google Scholar
  7. Ku, T. L. (1977) Rates of manganese accretion. In Marine Manganese Deposits (editor G. P. Glasby) Elsevier.Google Scholar
  8. Ku, T. L. and Broecker, W. S. (1969) Radiochemical studies on manganese nodules of deep-sea origin, Deep-Sea Res. 16, 625–637.Google Scholar
  9. Nikolayev, P. S. and Yefimova, E. I. (1963) On the age of iron-manganese concretions from the Indian and Pacific Oceans, Geokhimiya 7, 678–688.Google Scholar
  10. Spiess, F. N. and Greenslate, J. (1976) Preliminary cruise report, Pleiades Expedition Leg 4, Mn76-01. Seabed Assessment Program, IDOE-NSF, Technical Report No. 15, 87 p.Google Scholar

Copyright information

© Plenum Press, New York 1979

Authors and Affiliations

  • J. D. Macdougall
    • 1
  1. 1.Scripps Institution of Oceanography A-020La JollaUSA

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