Manganese nodules, Cobalt crusts, Suphides etc.

1. PRESENTATION ON
PRESENted by:
Swati
FRM Deptt.

2. Oceans cover 70 percent of Earth's surface.
They hold a veritable treasure trove of valuable resources.
They are the ultimate repository of many materials eroded or dissolved
from the land surface.
Sand and gravel, oil and gas have been extracted from the sea for many
years.
In addition, minerals transported by erosion from the continents to the
coastal areas are mined from the shallow shelf and beach areas.
These include diamonds off the coasts of South Africa and Namibia as
well as deposits of tin, titanium and gold along the shores of Africa, Asia
and South America.

3.  Ancient ocean deposits of sediments and evaporites now located
on land were originally deposited under marine conditions.
 These deposits are being exploited on a very large scale and in
preference to modern marine resources because of the
easier accessibility and lower cost of terrestrial resources.
 Yet the increasing population and the exhaustion of readily
accessible terrestrial deposits undoubtedly will lead to broader
exploitation of ancient deposits and increasing extraction directly
from ocean water and ocean basins.

4.  Efforts to expand ocean mining into deep-sea waters have recently
begun.
 The major focus is on manganese nodules, which are usually
located at depths below 4000 metres, gas hydrates (located
between 350 and 5000 metres), and cobalt crusts along the flanks
of undersea mountain ranges (between 1000 and 3000 metres), as
well as massive sulphides and the sulphide muds that form in
areas of volcanic activity near the plate boundaries, at depths of
500 to 4000 metres.

5. Manganese nodules
 Manganese nodules are lumps of minerals ranging in size from a
potato to a head of lettuce.
 They cover huge areas of the deep sea with masses of up to 75
kilograms per square metre.
 They are composed mainly of manganese, iron, silicates and
hydroxides.
 They grow around a crystalline nucleus at a rate of only about 1 to 3
millimetres per million years.
 The greatest densities of nodules occur off the west coast of Mexico
(in the Clarion-Clipperton Zone), in the Peru Basin, and the Indian
Ocean. In the Clarion-Clipperton Zone the manganese nodules lie on
the deep-sea sediments covering an area of at least 9 million square
kilometres – an area the size of Europe.

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

7. Cobalt crusts
 Cobalt crusts form at depths of 1000 to 3000 metres on the flanks of
submarine volcanoes.
 The crusts accumulate when manganese, iron and a wide array of trace
metals dissolved in the water (cobalt, copper, nickel, and platinum) are
deposited on the volcanic substrates.
 The content of cobalt (up to 2 per cent) and platinum (up to 0.0001 per
cent) is somewhat higher than in manganese nodules.
 Extracting cobalt from the ocean is of particular interest because it is
found on land in only a few countries (Congo, Zaire, Russia, Australia
and China).

8.  The mining of cobalt crusts is much more complex than manganese
nodules.
 For one, it is critical that only the crust is removed, and not the
underlying volcanic rocks.
 In addition, the slopes of the volcanoes are very ragged and steep,
which makes the use of excavation equipment more difficult.

9. Massive sulphides
 These are sulphur-rich ore that originates
at “black smokers”.
 These were first discovered in 1978 at the
East Pacific Rise.
 They are also located in comparatively
shallow water (less than 2000 metres)
and lie within the exclusive economic
zones of nations near them which makes
the possible mining more technologically
and politically feasible.
 Most occurrences are only a few metres
in diameter and the amount of material
present is negligible.
Massive sulphides form at black smokers – hot
springs on the sea floor with temperatures
approaching 400 degrees Celsius. These vents
discharge minerals from the Earth’s interior,
forming chimneys that rise to several metres
above the seabed.

10. Production of massive sulphides
 These occurrences of massive sulphides form at submarine plate
boundaries, where an exchange of heat and elements occurs between
rocks in the Earth’s crust and the ocean due to the interaction of
volcanic activity with seawater.
 Cold seawater penetrates through cracks in the sea floor down to
depths of several kilometres.
 Near heat sources such as magma chambers, the seawater is heated to
temperatures exceeding 4000C.
 Upon warming, the water rises rapidly again and is extruded back into
the sea. These hydrothermal solutions transport metals dissolved from
the rocks and magma, which are then deposited on the sea floor and
accumulate in layers.
 This is how the massive sulphides and the characteristic chimneys
(“black smokers”) are produced.

12. Other marine minerals found in seabed
 Gabbro
 Peridotite
 Basalt
 Olivine
 Serpentine

13. Gabbro
Dark in color -black or gray -and is a coarse-grained igneous rock that
makes up most of the seabed.
Dense type of rock formed from the slow cooling of magma chambers
beneath mid-ocean ridges.
Used in railroads, road material and can be polished to be sold as black
granite.
Basalt
Very similar to gabbro in its chemical composition.
Most often black in color.
Basalt is the most extrusive igneous rock.
Used as construction material, flooring and sculpting.
Peridotite
Textured with black, gray and white coloring.
Dense, intrusive igneous rock that is rich in magnesium and iron.
Contains olivine in its composition, another mineral found under
seabeds. Found as layers, crystals and fragmented blocks.
Named after the gemstone peridot. Used to capture and store
carbon dioxide.

14. Serpentine
Green in color, but can also be yellow, black or
brown.
It is an alteration form of the mineral olivine.
Used as a substitute for jade and can be used for
carving.
Olivine
 Brownish-green to dark or olive green in color.
 Commonly found in basalt, gabbro and peridotite.
 It is a silicate mineral, which are common rock formers.
 It is used in jewellery, as peridot, when mixed with
peridotite.

16. Deep sea mining
 Deep-sea mining is the process of retrieving mineral deposits from
the deep sea – the area of the ocean below 200 m which covers
about 65% of the Earth’s surface.
 Depleting terrestrial deposits and rising demand for metals are
stimulating interest in the deep sea, with commercial
mining imminent.
 China is the world’s largest consumer and importer of minerals and
metals.

17. Ocean mining in India
 India’s ambitious ‘Deep Ocean Mission’ is all set to be launched this year.
 Dr. Madhavan Rajeevan, Secretary, Union Ministry of Earth Sciences,
announced on July 27 that the ₹8,000-crore plan to explore deep ocean
minerals will start from October.

18. What will be mined from the deep ocean?
 One of the main aims of the mission is to explore and extract
polymetallic nodules.
 These are small potato-like rounded accretions composed of
minerals such as manganese, nickel, cobalt, copper and iron
hydroxide.
 They lie scattered on the Indian Ocean floor at depths of about
6,000 m and the size can vary from a few millimetres to centimetres.
 These metals can be extracted and used in electronic devices,
smartphones, batteries and even for solar panels.

19. Where will the team mine?
 The International Seabed Authority (ISA), an autonomous
international organisation established under the 1982 United
Nations Convention on the Law of the Sea, allots the ‘area’ for deep-
sea mining.
 India was the first country to receive the status of a ‘Pioneer
Investor ‘ in 1987 and was given an area of about 1.5 lakh sq km in
the Central Indian Ocean Basin (CIOB) for nodule exploration.
 In 2002, India signed a contract with the ISA and after complete
resource analysis of the seabed 50% was surrendered and the
country retained an area of 75,000 sq km.

20. According to a release from the Ministry of Earth Sciences, the
estimated polymetallic nodule resource potential in this area is 380
million tonnes (MT), containing 4.7 MT of nickel, 4.29 MT of copper,
0.55 MT of cobalt and 92.59 MT of manganese.

23. Impacts of mining
The following impacts of mining activities could affect its biodiversity and
ecosystems:
(i)Disturbance of the seafloor
 The scraping of the ocean floor by machines can alter or destroy deep-
sea habitats, leading to the loss of species and fragmentation or loss of
ecosystem structure and function.
 Many species living in the deep sea are endemic and physical
disturbances in just one mining site can possibly wipe out an entire
species.
 This is one of the biggest potential impacts from deep-sea mining.

24. (ii)Sediment plumes
Some forms of deep-sea mining will stir up fine sediments on the
seafloor consisting of silt, clay and the remains of microorganisms,
creating plumes of suspended particles.
(iii)Pollution
Species such as whales, tuna and sharks could be affected by noise,
vibrations and light pollution caused by mining equipment and
surface vessels, as well as potential leaks and spills of fuel and toxic
products.

25. Mitigation strategies
Baseline studies
 Comprehensive baseline studies are needed to understand what species
live in the deep sea, how they live, and how they could be affected by
mining activities.
 More funds are needed for training and educational programmes
focused on improving our understanding of the deep sea.
Circular economy
 The repair, recycling and reuse of products should be encouraged to
help reduce the demand for raw materials from the deep sea.
 Enhancing product design to make use of less or alternative materials
can also reduce the demand.

26. Environmental impact assessments
 High-quality environmental assessments are needed to assess the
full range, extent and duration of environmental damage from deep-
sea mining operations.
 These assessments are also needed to ensure that the loss of
biodiversity as a result of mining operations is properly accounted
for in mining regulations set by authorities, well before any decision
to mine is approved.

28. REFERENCES:
 https://www.thehindu.com › Sci-Tech › Science
 https://worldoceanreview.com › wor-1 › energy ›
marine-minerals
 www.waterencyclopedia.com › Mi-Oc
 https://portals.iucn.org › library › sites › library › files ›
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