MANGANESE NODULES

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MANGANESE NODULES

• by
• Mark Sparks

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Introduction

• First discovered by the HMS Challenger expedition
  in 1873
• Resemble misshapen metallic snowballs
• Found in all the major ocean basins
• Also known as ferromanganese or polymetallic
  nodules

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Composition

• Manganese dioxide average 30 percent by weight
• Iron oxide average 20 percent by weight
• Other elements average less than 2 percent by
  weight
• Fragments serves as a nucleus
• Nucleus made of carbonates, phosphates, zeolites,
  clays, and silicas

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Origin

• Deep-ocean water lacks significant quantities of
  manganese or iron
• Three possible sources of the manganese and iron
• Weathering of volcanic material on the ocean
  floor
• High concentrations of manganese and iron in
  hydrothermal waters at spreading centers
• Runoff from land
• Purely chemical or bacterial by-product
• Bacteria using manganese and iron oxidation in
  their metabolic process theory

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Occurrences

• Most commonly found on the ocean floors
• Can form on lake bottoms
• Highest concentrations found on vast abyssal
  plains in the deep ocean
• 4,000 and 6,000 meters
• Estimated that approximately two billion metric
  tons of manganese nodules lie on the ocean floors
  around the world

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Growth Rates

• Extremely slow growth rates
• Adding 1 mm to 200 mm per million years
• Correlation between the biological productivity
  of overlying water and the composition and growth
  rates of manganese nodules
• Biologically unproductive
• Rich in iron and cobalt
• Grow at a rate less than 5 mm permillion years
• Moderate biological productivity
• High concentrations of nickel, copper, and
  manganese
• Growth rate 5 mm to 10 mm per million years
• very productive biological waters
• Rich in manganese but poor in copper, nickel, and
  cobalt
• Grow at a rate of 10 mm to 200 mm per million
  years

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Economical Prospects

• Caught the attention of mining companies around
  1960
• Nearly half billion dollars spent researching
  economical value
• Interest has faded due to a depressed metals
  market

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Conclusion

• Exact process of formation is uncertain
• Result of sediment accumulating around a central
  nucleus
• Source of the manganese and iron in the ocean
  waters
• Volcanic activity on the ocean floor
• Hydrothermal waters at spreading centers
• Runoff that carries minerals as soluble compounds
  from land
• Found in all oceans around the world
• Extremely slow growth rates
• lt 200 mm per million years
• Economical value in the metals
• Cost of extracting from deep ocean basins far
  outweigh the current rate on the metals market

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Any Questions?