Marine Mineral Resources and Law of the Sea -1 | Geology Optional Notes for UPSC PDF Download

Marine Mineral Resources

Definition

• Marine mineral resources refer to mineral accumulations that develop on or below the seafloor, from which metals, minerals, elements, or aggregates can be extracted as valuable resources.

Types of Marine Mineral Resources

• Manganese Nodules
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  • Found at depths of less than 4000 meters.
• Gas Hydrates
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  • Located between 350 and 5000 meters below the sea surface.
• Cobalt Crusts
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  • Form along the flanks of undersea mountain ranges at depths ranging from 1000 to 3000 meters.
• Massive Sulfides and Sulfide Muds
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  • Develop in areas of volcanic activity near plate boundaries, typically at depths of 500 to 4000 meters.

Utilization of Marine Mineral Resources

• Historically, the seafloor has been exploited for resources such as sand, gravel, oil, and gas.

Mineral Recovery from the Seabed

Overview

• Advancements in mineral recovery from the seabed and exploration of new marine mineral sources have progressed rapidly in recent years, offering significant economic benefits and the potential for valuable additions to the global resource supply.

Types of Marine Minerals

• Commercial exploitation has primarily focused on solid marine minerals originating from the mechanical and chemical erosion of continental rocks, which are then carried to the ocean by rivers.
• These minerals are typically found in shallow offshore regions within the territorial sea and the exclusive economic zone extending up to 200 nautical miles.

Placer Deposits

• Minerals resulting from the mechanical erosion of continental rocks are concentrated in placer deposits, which are sorted by water movement based on the varying density of constituent minerals.
• Examples of minerals found in placer deposits include heavy metallic elements like gold, iron, and rare earth elements, as well as nonmetals like diamonds and siliceous sand.

Manganese Nodules

• Manganese nodules are mineral formations ranging in size from a potato to a head of lettuce, primarily composed of manganese, iron, silicates, and hydroxides.
• These nodules grow slowly, at a rate of 1 to 3 millimeters per million years, around a crystalline nucleus through the precipitation of chemical elements from seawater or pore waters in underlying sediments.

The Formation of Cobalt-Rich Ferromanganese Crusts

• Cobalt-rich ferromanganese crusts are metallic mineral resources that contain metals sourced from both land and sea origins.
• These crusts are typically thin layers, reaching up to 25 centimeters in thickness, found on volcanic rocks located on seamounts and submerged volcanic mountain ranges.
• They are situated at varying water depths, ranging from 400 to 4,000 meters.
• The most concentrated deposits of these crusts are located in and around the exclusive economic zones of certain western Pacific island nations.
• If mining and refining technologies advance, a single seabed mining site has the potential to contribute up to 25% of the global market's annual demand for cobalt.

Formation Process of Cobalt-Rich Ferromanganese Crusts

• Cobalt-rich ferromanganese crusts come into existence by incorporating metals from both land and sea sources.
• These crusts form as thin layers on volcanic rocks of seamounts and submerged volcanic mountain ranges through the process of seawater precipitation.
• When elements like manganese, iron, and various trace metals present in water (such as cobalt, copper, nickel, platinum) settle on volcanic substrates, crusts begin to develop.

Polymetallic Massive Sulphides Formation

• Polymetallic massive sulphides are created by magma upwelling beneath submerged volcanic mountain ranges.
• This magma heating the seafloor leads to the formation of seafloor hot springs known as black smokers.
• These occurrences take place at submarine plate boundaries, where the interaction between volcanic activity and seawater results in the exchange of heat and elements between the earth's crust rocks and the ocean.
• Metals dissolved in rocks are carried by hydrothermal solutions to create polymetallic massive sulphides.

Discovery of Polymetallic Massive Sulphides

• Polymetallic massive sulphides were first identified as minerals in oceanic environments in 1979, having been previously known only from deposits mined on land for metals like copper, iron, zinc, silver, and gold since ancient times.

Formation of Mineral Deposits in Marine Environments

• Seafloor Hot Springs and Formation of Massive Sulphides

  Massive sulphides are created around seafloor hot springs, notably black smokers, which derive heat from magma upwelling beneath submerged volcanic mountain ranges.

• Seafloor Spreading and New Seafloor Creation

  During seafloor spreading, magma cools and solidifies, generating fresh seafloor segments that move like opposing conveyor belts on either side of the underwater mountain range.

• Formation of Limestones in Tropical Oceans

  Limestones are abundantly forming in tropical to semitropical oceans due to the precipitation by a variety of biological organisms like mollusks, corals, and plants.

• Magnesium Extraction from Seawater

  Magnesium is the sole metal extracted from seawater, present in a dissolved state at a concentration of approximately 1000 ppm.

• Phosphate-Rich Crust Formation

  In shallow marine environments, complex organic and inorganic processes lead to the constant precipitation of phosphate-rich crust and granules.