Deep sea mining
Deep sea mining is the extraction of minerals from the seabed of the deep sea. The main ores of commercial interest are polymetallic nodules, which are found at depths of primarily on the abyssal plain. The Clarion–Clipperton zone alone contains over 21 billion metric tons of these nodules, with minerals such as copper, nickel, cobalt and manganese making up roughly 30% of their weight. It is estimated that the global ocean floor holds more than 120 million tons of cobalt, five times the amount found in terrestrial reserves.
, only exploratory licenses have been issued, with no commercial-scale deep sea mining operations yet. The International Seabed Authority regulates all mineral-related activities in international waters and has granted 31 exploration licenses so far: 19 for polymetallic nodules, mostly in the CCZ; 7 for polymetallic sulphides in mid-ocean ridges; and 5 for cobalt-rich crusts in the Western Pacific Ocean. There is a push for deep sea mining to commence by 2025, when regulations by the ISA are expected to be completed.
In April 2025, U.S. President Trump signed an Executive Order instructing the National Oceanic and Atmospheric Administration to expedite permits for companies to mine in both international and U.S. territorial waters, citing the Deep Seabed Hard Minerals Resource Act of 1980.
Deep sea mining is being considered in the exclusive economic zone of countries, such as Norway, where in January 2024 the government announced its intention to allow companies to apply for exploration permits in 2025. In December 2024, Norway's plans to begin awarding exploration licenses were temporarily put on hold after the Socialist Left Party blocked the planned licensing round as part of negotiations over the government budget. In 2022, the Cook Islands Seabed Minerals Authority granted three exploration licenses for cobalt-rich polymetallic nodules within their EEZ. In 2025, it was announced that the Cook Islands had signed a deal with China focused on deep-sea mining. Papua New Guinea was the first country to approve a deep sea mining permit in state waters for the Solwara 1 project, despite three independent reviews highlighting significant gaps and flaws in the environmental impact statement.
The most common commercial model of deep sea mining proposed involves a caterpillar-track hydraulic collector and a riser lift system bringing the harvested ore to a production support vessel with dynamic positioning, and then depositing extra discharge down the water column below 2,000 meters. Related technologies include robotic mining machines, as surface ships, and offshore and onshore metal refineries. Though largely composed of nickel and manganese which are most widely used as key inputs into the steel industry, wind farms, solar energy, electric vehicles, and battery technologies use many of the deep-sea metals. Electric vehicle batteries are a key driver of the critical metals demand that incentivizes deep sea mining, as well as demands for the production of aerospace and defense technologies, and infrastructure.
The environmental impact of deep sea mining is controversial. Environmental advocacy groups such as Greenpeace and the Deep Sea Mining Campaign claimed that seabed mining has the potential to damage deep sea ecosystems and spread pollution from heavy metal-laden plumes. Critics have called for moratoria or permanent bans. Opposition campaigns enlisted the support of some industry figures, including firms reliant on the target metals. Individual countries like Norway, Cook Islands, India, Brazil and others with significant deposits within their exclusive economic zones are exploring the subject.
As of 2021, the majority of marine mining used dredging operations in far shallower depths of less than 200 m, where sand, silt and mud for construction purposes is abundant, along with mineral rich sands containing ilmenite and diamonds.
Deposit types
Deep sea ore deposits are classified into three main types: polymetallic nodules, polymetallic sulfide deposits, and cobalt-rich crusts.Polymetallic nodules
Polymetallic nodules are found at depths of in all major oceans, though due to their metallic composition those in the Pacific Ocean are of greatest commercial interest. Nodules may also be found in shallow waters like the Baltic Sea and in freshwater lakes. They are the most readily minable type of deep sea ore. These nodules typically range in size from 4–14 cm in diameter, though some can be as large as 15 cm.Manganese and related hydroxides precipitate from ocean water or sediment-pore water around a nucleus, which may be a shark's tooth or a quartz grain, forming potato-shaped nodules some in diameter. They accrete at rates of 1–15 mm per million years. These nodules are rich in metals including rare earth elements, cobalt, nickel, copper, molybdenum, and yttrium.
The Clipperton fracture zone hosts the world's largest deposit nickel resource. These nodules sit on the seafloor and require no drilling or excavation. Nickel, cobalt, copper and manganese make up nearly 30% of the contents.
| Location | Manganese | Iron | Nickel | Copper | Cobalt | Total REE |
| CCZ | 28.4 | 6.16 | 1.30 | 1.07 | 0.210 | 0.0813 |
| Eastern CCZ | 31.4 | 6.3 | 1.40 | 1.18 | 0.174 | 0.0701 |
| Western CCZ | 27.56 | 6.1 | 1.36 | 1.08 | 0.250 | 0.0801 |
| Indian Ocean | 24.4 | 7.14 | 1.10 | 1.04 | 0.111 | 0.1039 |
| Cook Islands | 16.1 | 16.1 | 0.38 | 0.23 | 0.411 | 0.1678 |
| Peru Basin | 34.2 | 6.12 | 1.30 | 0.60 | 0.048 | 0.0403 |
Polymetallic sulfides
Polymetallic or sulfide deposits form in active oceanic tectonic settings such as island arcs and back-arcs and mid ocean ridge environments. These deposits are associated with hydrothermal activity and hydrothermal vents at sea depths mostly between and therefore located in shallower waters to other marine mineral types like polymetallic nodules. These minerals are rich in copper, gold, lead, silver and others.Polymetallic sulphides appear on seafloor massive sulfide deposits. They appear on and within the seafloor when mineralized water discharges from a hydrothermal vent. The ionic metals and sulfides in the hot, mineral-rich water precipitate upon contact with cold seawater. The stock area of the chimney structures of hydrothermal vents can be highly mineralized.
Cobalt-rich crusts
Cobalt-rich crusts form on sediment-free rock surfaces around oceanic seamounts, ocean plateaus, and other elevated features. The deposits are found at depths of and form 'carpets' of metal-rich layers about thick at the feature surface. Crusts are rich in a range of metals including cobalt, tellurium, nickel, copper, platinum, zirconium, tungsten, and rare earth elements. Temperature, depth and seawater sources shape how the formations grow.Cobalt-rich formations exist in two categories depending on the depositional environment:
- hydrogenetic cobalt-rich ferromanganese crusts grow at 1–5 mm/Ma, but offer higher concentrations of critical metals.
- hydrothermal crusts and encrustations precipitate quickly, near 1600–1800 mm/Ma, and grow in hydrothermal fluids at approximately
| Type | Typical depth range | Resources |
| Polymetallic nodules Manganese nodules | 4,000 – 6,000 m | Nickel, copper, cobalt, and manganese |
| Manganese crusts | 800 – 2,400 m | Mainly cobalt, some vanadium, molybdenum and platinum |
| Polymetallic sulfide deposits | 1,400 – 3,700 m | Copper, lead and zinc, some gold and silver |
Diamonds are mined from the seabed by De Beers and others.
Deposit sites
Deep sea mining sites hold polymetallic nodules or surround active or extinct hydrothermal vents at about depth. The vents create sulfide deposits, which collect metals such as silver, gold, copper, manganese, cobalt, and zinc. The deposits are mined using hydraulic pumps or bucket systems.The largest deposits occur in the Clarion–Clipperton zone in the Pacific Ocean. It stretches over 4.5 million square kilometers of the Northern Pacific Ocean between Hawaii and Mexico. Scattered across the abyssal plain are trillions of polymetallic nodules, potato-sized rocklike deposits containing minerals such as manganese, nickel, copper, zinc, and cobalt.
The Cook Islands contains the world's fourth largest deposit in the South Penrhyn basin close to the Manihiki Plateau.
Though the nodule fields of greatest commercial interest are located in the eastern Pacific, polymetallic nodules are also found within the Mid-Atlantic Ridge system, around Papua New Guinea, Solomon Islands, Vanuatu, and Tonga, and the Peru Basin.
Cobalt-rich crusts are found on seamounts in the Atlantic and Indian Ocean, as well as countries such as the Pacific Federated States of Micronesia, Marshall Islands, and Kiribati.
On November 10, 2020, the Chinese submersible Striver reached the bottom of the Mariana Trench 10,909 meters. Chief designer Ye Cong said the seabed was abundant with resources and a "treasure map" can be made.
Promising sulfide deposits were found in the Central and Eastern Manus Basin around Papua New Guinea and the crater of Conical Seamount to the east. It offers relatively shallow water depth of 1050 m, along with a nearby gold refinery.