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The understanding and knowledge of marine mineral resources in India have grown in tandem with the advancements in geological studies. As a result, the recovery of these resources has sped up. Earlier, the exploration, extraction, and exploitation of solid mineral resources were limited to those which arose from natural weathering of terrestrial rocks and were carried offshore. Now, the rising demand and technological development have encouraged the examination of minerals on the ocean floor as well.
Classification of marine mineral resources
Based on their origin, marine mineral resources can be classified into three types.
Mineral deposits from the terrestrial sources in the sea
These mineral resources were formed by the deposition of materials formed by the chemical or mechanical weathering of rocks on land. These materials were carried to the oceans by the rivers and dissolved in the water. Once in the ocean, these materials were sorted by the ocean waves based on their density.
Marine minerals that have originated from terrestrial sources contain heavy metals such as gold, iron, tin, barium, chromium, zirconium, etc. These resources also contain non-metals like a diamond, lime, silica, etc. Coastlines of many nations like India, Australia, and Brazil are regions where most of these minerals have been discovered. However, gold mining is common in the coastal areas of Thailand, Myanmar, and Indonesia.
Marine mineral deposits from terrestrial and deep ocean sources
These mineral deposits under the ocean are contributed by both terrestrial and deep-sea resources. These deposits are classified into various types. Some of these are discussed below.
Polymetallic nodulesÂ
These are also called manganese nodules. These were the first minerals to be obtained from the seafloor during the Challenger expedition (1872-1876). Polymetallic nodules have extraction and refining costs and thus have greater economic value. The United Nations Convention on the Law of the Sea was formed after the potential economic worth of these minerals were discovered. This convention ensured fair distribution of predicted incoming wealth among countries.
Ferromanganese crusts with a high cobalt content
These are formed in the same way in which the manganese nodules are formed. These crusts are typically found on hard rock platforms, such as abyssal hills, plateaus, and ocean ridges, and are washed off by ocean waves. Ferromanganese crusts are made up of cobalt, nickel, platinum, titanium, manganese and iron. These can reach a thickness of 25 cm and are found 400-4000 metres deep in the ocean.
Marine minerals derived from ocean basin sources
These deposits were formed by the weathering of rocks and the deposition of minerals on the ocean floor. Some important ones are as follows:
Metalliferous sediments: These are the most significant mineral deposits to have been discovered. These were put to light for the first time in the year 1965. Metalliferous sediments are found in the Atlantis 2nd Deep, a parallelogram-shaped basin at a depth of two kilometres. They comprise the oldest hydrothermal deposits formed on submerged plate boundaries. It is the largest basin between the Arabian and African plates.
Seafloor massive sulphides
These are large bodies made up of metallic sulphides. These are formed at or near the seabed by the mixing of hot-spring fluids with cold seawater at depths of 1000–3000 m. Very high pressure at these depths results in boiling. It has been reported that in these circumstances, the circulation of water through the ocean bed is the major cause of massive sulphide formations.Â
Conclusion
Marine mineral resources are potential sources of numerous minerals. However, the extraction of these resources poses more challenges than the extraction of terrestrial reserves. Although marine mineral resources have immense potential to enhance economic growth, their worth will be realised only through proper assessment, analysis, and political coordination.
