Manganese nodules are rock concretions found on ocean floors that form over millions of years around a core. They consist of layers of manganese, iron, silicates and hydroxides precipitated from seawater. There are three main theories for their origin: weathering of volcanic material, hydrothermal vents, or bacterial activity. They occur in abyssal plains at depths of 4,000-6,000 meters and contain valuable metals like manganese, iron, nickel, copper and cobalt. India has exploration programs to assess extracting polymetallic nodules from the Central Indian Ocean Basin for industrial applications.

1. MANGANESE NODULES
Yuiyo shishak
yuiyoshishak@yahoo.com

2. CONTENTS
• Introduction
• Origin
• Occurrence
• Economical prospects
• Conclusion
• References

3. INTRODUCTION
• Manganese nodules are also called Polymetallic
nodules are rock concretions on the sea bottom
formed of concentric layers of iron and manganese
hydroxide around a core.
• They are composed mainly of manganese, iron,
silicates and hydroxides, and they grow around a
crystalline nucleus at a rate of only about one to 3
millimetres per million years. The chemical elements
are precipitated from seawater or originate in the
pore waters of the underlying sediments.

4. Cross-section view of a
manganese nodule: Over
millions of years, minerals are
deposited around a nucleus

5. 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

6. HOW NODULE FORMS
• The formation of manganese nodules is
conceivably simple
• The growth process can take place n two
ways:
I. The hydrogenous process
II. The diagenetic process

7. • THE HYDROGENOUS PROCESS
 The metal compounds sinking through the
water are precipitated
Up to 10mm per million year
formed due to slow deposition of metals out
of sea water and characterized by a high
concentration of base metals and varying
Mn/Fe ratios (from 0.5 -5)

8. • THE DIAGENETIC PROCESS
 Does not occur in the water column but within the
sediments
 Between 10 and 100mm
 characterized by high Mn/Fe ratios and relatively low
concentration of base metals.

9. Other classification
• The Derivation Of Metals From Hot
Springs Associated With Volcanic
Activity (Hydrothermal),
• The Decomposition Of Basaltic Debris By
Seawater (Halmyrolitic) And
• The Precipitation Of Metal Hydroxides Through
The Activity Of Microorganisms (Biogenic).
• Several Of These Processes May Operate
Concurrently Or They May Follow One Another
During The Formation Of A Nodule

11. Nodules on the Seabed

12. CHEMICAL COMPOSITION
• The major elements in nodules are oxygen ,
manganese , iron , silica ,lesser amount of aluminium
, calcium , sodium and magnesium and hence
elements nickel , copper and cobalt are of greatest
economic interest
• Manganese dioxide average 30 percent by weight
• Iron oxide average 20 percentage by weight
• Other elements average less than 2 percent by
weight
• Fragments serves as a nucleus
• Nucleus made of carbonates, phosphates, zeolites ,
clays, and silicates

14. 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
 Manganese nodules occur in many different environment
including freshwater lakes , continental shelves , seamount
on abyssal plains.

16. MANGANESE NODULES:RELEVANCE TO
INDIA
• Potential Resource Of Metal In Central Indian
Ocean Basin
• Carrying Out The Exploration And Technology
Development From exploitation Of polymetallic
nodules Under The Polymetallic Nodule
Program(PMN) Of The Ministry Of Earth Science
• Only Country With Mining Site Allocated In Indian
Ocean
• Other Site Are Claimed In The Pacific Ocean

17. ECONOMICAL USES
• It is these alloys, rather than manganese ore
itself , which are used in most metallurgical
applications.
• seafloor manganese nodules are often rich in
manganese , iron , nickel ,copper and cobalt.
• Manganese is used as alloy with metals such
as aluminium and copper
• Non metallurgical uses include battery
cathodes

18. CONCLUSION
 Runoff that carries minerals as soluble
compounds from land
 Found in all oceans around the world
 Extremely slow growth rates
 < 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

19. REFERENCES
• The geology of Ore Deposits. Guilbert . And
Park1975.
• G P Glasby ,1975. Marine manganese
nodules.v,15 PP. 25-27, pp. 70 and p.142
• Worldoceanreview.com>mineral-resources
• Geology.com>metals