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)


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.


Alpha Particle Alpha Activity Track Density Nodule Surface Manganese Nodule 
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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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