Deep-sea Mining

Deep sea mining is a growing subfield of experimental seabed mining that involves the retrieval of minerals and deposits from the ocean floor found at depths of or greater. As of 2021, the majority of marine mining efforts are limited to shallow coastal waters only, where sand, tin and diamonds are more readily accessible. There are three types of deep sea mining that have generated great interest: polymetallic nodule mining, polymetallic sulphide mining, and the mining of cobalt-rich ferromanganese crusts. The majority of proposed deep sea mining sites are near of polymetallic nodules or active and extinct hydrothermal vents at below the ocean’s surface. The vents create globular or massive sulfide deposits, which contain valuable metals such as silver, gold, copper, manganese, cobalt, and zinc. The deposits are mined using either hydraulic pumps or bucket systems that take ore to the surface to be processed.

Marine minerals include sea-dredged and seabed minerals. Sea-dredged minerals are normally extracted by dredging operations within coastal zones, to maximum sea depths of about 200 m. Minerals normally extracted from these depths include sand, silt and mud for construction purposes, mineral rich sands such as ilmenite and diamonds.

As with all mining operations, deep sea mining raises questions about its environmental impact. There is a growing debate about whether deep sea mining should be allowed or not. Environmental advocacy groups such as Greenpeace and the Deep Sea Mining Campaign have argued that seabed mining should not be permitted in most of the world's oceans because of the potential for damage to deep sea ecosystems and pollution by heavy metal-laden plumes. Prominent environmental activists and state leaders have also called for moratoriums or total bans due to the potential of devastating environmental impacts. Some argue that there should be a total ban on seabed mining. Some anti-seabed mining campaigns have won the support of large industry such as some of the technology giants, and large car companies. However, these same companies will be increasingly reliant on the metals seabed minerals can provide. Some scientists argue that seabed mining should not go ahead, as we know such a relatively small amount about the biodiversity of the deep ocean environment. Individual countries with significant deposits of seabed minerals within their large EEZ’s are making their own decisions pertaining to seabed mining, exploring ways of undertaking seabed mining without causing too much damage to the deep ocean environment, or deciding not to develop seabed mines.
Some companies are attempting to build polymetallic deep sea mining equipment which does no serious harm and preservers the marine habitat.

As of 2022 there was no commercial mining of seabed minerals. However, the International Seabed Authority has granted 19 exploration licenses for polymetallic nodules, within the Clarion Clipperton Zone.
The Cook Islands Seabed Minerals Authority (SBMA) has granted 3 exploration licenses for polymetallic nodules within their EEZ.

There is the potential for mining at a range of scales within the oceans from small to very large. Technologies involved in the mining of seabed minerals would be highly technological, and involve a range of robotic mining machines, as well as surface ships, and metal refineries at onshore locations. One vision for the post-fossil fuel world will rely on wind farms, solar energy, electric cars, and improved battery technologies: these use a high volume and wide range of metallic commodities including ‘green’ or ‘critical’ metals many of which are in relatively short supply. Seabed mining could provide a near-term solution to the provision of many of these metals, though only serves to worsen the fundamental problems posed by extraction.SPC (2013)
Deep Sea Minerals: Deep Sea Minerals and the Green Economy
. Baker, E., and Beaudoin, Y. (Eds.) Vol. 2, Secretariat of the Pacific Community

Mining sites

Deep sea mining is a relatively new mineral retrieval process undergoing research which takes place on the ocean floor. Ocean mining sites are usually around large areas of polymetallic nodules or active and extinct hydrothermal vents at about 3,000 – 6,500 meters below the ocean's surface. The vents create sulfide deposits, which contain precious metals such as silver, gold, copper, manganese, cobalt, and zinc. The deposits are mined using either hydraulic pumps or bucket systems that take ore to the surface to be processed.

Types of minerals

Seabed minerals are mostly located between 1 and 6 km beneath the ocean surface and comprise three main types:

* Polymetallic or Manganese nodules are found between 4 and 6 km beneath the sea surface, largely within abyssal plain environments. 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 4–14 cm in diameter. They accrete very slowly at rates of 1–15 mm per million years. Polymetallic/Manganese nodules are rich in many elements including rare earths, cobalt, nickel, copper, molybdenum, lithium, and Yttrium. The largest deposits of Polymetallic Nodules occur in the Pacific Ocean between Mexico and Hawaii in an area called the Clarion Clipperton Fracture Zone. The Cook Islands contains the world’s fourth largest Polymetallic Nodule deposit in an area called the South Penrhyn basin close to the Manihiki Plateau.
* Polymetallic or seabed massive sulfide deposits that 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 of mostly between 1 and 4 km. Polymetallic Sulfide minerals are rich in copper, gold, lead, silver and other metals. They are found within the Mid Atlantic Ridge system, around Papua New Guinea, Solomon Islands, Vanuatu, and Tonga and other similar ocean environments around the world.
* Cobalt-rich crusts (CRC’s) form on sediment free rock surfaces, around oceanic seamounts, ocean plateau and other elevated topographic features within the ocean. The deposits are found at depths of 600–7000 m beneath sea level and form ‘carpets’ of polymetallic rich layers about 30 cm thick at the surface of the elevated features. Crusts are rich in a range of metals including cobalt, tellurium, nickel, copper, platinum, zirconium, tungsten and rare earth elements. They are found in many parts of all oceans such as seamounts in the Atlantic and Indian Oceans, as well as countries such as the Federated States of Micronesia, Marshall Islands, and Kiribati.

The deep sea contains many different resources available for extraction, including silver, gold, copper, manganese, cobalt, and zinc. These raw materials are found in various forms on the sea floor.

Diamonds are also mined from the seabed by De Beers and others.

Cobalt-rich ferromanganese formations are found at various depths between 400 and 7000 meters below sea level (masl). These formations are a type of Manganese crust deposits. The substrates of rock consist of layered iron and Magnesium layers ( Fe-Mn oxyhydroxide deposits ) that will host mineralization.

Cobalt-rich ferromanganese formations exist in two categories depending on the Depositional environment, (1) hydrogenetic cobalt-rich ferromanganese crusts and (2) hydrothermal crusts and encrustations. Temperature, depth and sources of seawater are dependent variables that shape how the formations grow. Hydrothermal crusts precipitate quickly, near 1600–1800 mm/Ma and grow in hydrothermal fluids at approximately 200 °C. Hydrogenetic crusts grow much slower at 1–5 mm/Ma but will have higher concentrations of critical metals.

Submarine seamount provinces, linked to hotspots and seafloor spreading, vary in depth along the ocean floor. These seamount show characteristics distribution that connects them to Cobalt-rich ferromanganese formation. In Western Pacific, a study conducted at <1500 m to 3500 m (mbsl) proved that the cobalt crusts are concentrated in the seamount section that slops at less than 20°. The high-grade cobalt crust in the Western Pacific trended /correlated with latitude and longitude, a high region within 150°E‐140°W and 30°S‐30°N

Polymetallic sulphides are resources available for extraction from Seafloor massive sulfide deposits, composed on and within the seafloor base when mineralized water discharges from Hydrothermal vent. The hot mineral-rich water precipitates and condenses when released from hydrothermal vents and meets the cold seawater. The stock area of the chimney structures of hydrothermal vents can be highly mineralized.

Polymetallic nodules/manganese nodules are founded on Abyssal plain, in a range of sizes, some as large as 15 cm long. The Clipperton Fracture Zone (CCZ) is a well known area of occurrences. Nodules are recorded to have average growth rates near 10–20 mm/Ma.

The Clipperton Fracture Zone is host to the largest untapped deposit nickel resource; Polymetallic nodules or Manganese nodule sit on the seafloor. These nodules require no need for drilling or typical Surface mining techniques. The composition of nickel, cobalt, copper and manganese make up nearly 100% of the nodules, and generates no toxic tailings. Polymetallic nodules in the Clipperton Fracture Zone are currently being studied to produce battery metals.

Deep sea mining efforts

Over the past decade, a new phase of deep-sea mining has begun. Rising demand for precious metals in Japan, China, Korea and India has pushed these countries in search of new sources. Interest has recently shifted toward hydrothermal vents as the source of metals instead of scattered nodules. The trend of transition towards an electricity-based information and transportation infrastructure currently seen in western societies further pushes demands for precious metals. The current revived interest in phosphorus nodule mining at the seafloor stems from phosphor-based artificial fertilizers being of significant importance for world food production. Growing world population pushes the need for artificial fertilizers or greater incorporation of organic systems within agricultural infrastructure.

The world's first "large-scale" mining of hydrothermal vent mineral deposits was carried out by Japan in August - September, 2017. Japan Oil, Gas and Metals National Corporation (JOGMEC) carried out this operation using the Research Vessel Hakurei. This mining was carried out at the 'Izena hole/cauldron' vent field within the hydrothermally active back-arc basin known as the Okinawa Trough which contains 15 confirmed vent fields according to th
InterRidge Vents Database

A deep sea mining venture in Papua New Guinea, the Solwara 1 Project, was granted a mining permit to begin mining a high grade copper-gold resource from a weakly active hydrothermal vent. This controversial project generated an enormous backlash from the community and environmental activists The Solwara 1 Project was located at 1600 metres water depth in the Bismarck Sea, New Ireland Province. Using ROV (remotely operated underwater vehicles) technology developed by UK-based Soil Machine Dynamics, Nautilus Minerals Inc. was the first company of its kind to announce plans to begin full-scale undersea excavation of mineral deposits."Treasure on the ocean floor"
. ''Economist'' 381, no. 8506: 10. (30 November 2006) However a dispute with the government of Papua-New Guinea delayed production and operations until early 2018. In September 2019, it was announced that the project had collapsed as Nautilus Minerals Inc. went into administration and its major creditors sought to recoup the millions of dollars they had sunk into the project. The Prime Minister of Papua New Guinea called the project a "total failure", sparking calls for a deep sea mining moratorium from his Pacific counterparts.

An additional site that is being explored and looked at as a potential deep sea mining site is the Clarion-Clipperton Fracture Zone (CCZ). The CCZ 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 magnesium, nickel, copper, zinc, cobalt, and others. Development of technologies to collect polymetallic nodules in the CCZ began in the 1970s when oil, gas and mining majors including Shell, Rio Tinto (Kennecott) and Sumitomo, conducted pilot test work, recovering over ten thousand tons of nodules. Polymetallic nodules are also abundant in the Central Indian Ocean Basin and the Peru Basin. Mining claims registered with the International Seabed Authority (ISA) are mostly located in the CCZ, most commonly in the manganese nodule province. The ISA has entered into 18 different contracts with private companies and national governments to explore the suitability of polymetallic nodule mining in the CCZ.

In 2019, the government of the Cook Islands passed two legislative bills pertaining to deep sea mining in the country's EEZ. The ''Sea Bed Minerals (SBM)'' ''Act of 2019'' was passed to "enable the effective and responsible management of the seabed minerals of the Cook Islands in a way that also...seeks to maximize the benefits of seabed minerals for present and future generations of Cook Islanders." Sea Bed Minerals (Exploration) Regulations Act and the Sea Bed Minerals Amendment Act were passed by Parliament in 2020 and 2021 respectively. As much as 12 billion tons of polymetallic nodules are spread across the ocean floor in the Cook Island's EEZ. The nodules found in the EEZ contain cobalt, nickel, manganese, titanium, and Rare Earth Elements.

On November 10, 2020, the Chinese submersible Fendouzhe reached the bottom of the Mariana Trench 10,909 meters (35,790 feet). It didn't surpass the record of American undersea explorer Victor Vescovo who claimed 10,927 meters (35,853 feet) in May 2019. Chief designer of the submersible, Ye Cong said the seabed was abundant with resources and a "treasure map" can be made of the deep sea.

Extraction methods

Each of the different deep sea mining resource will involve different technology.

New robotics and AI solutions are in development to minimize the environment damage and improve the economics.

Recent technological advancements have given rise to the use remotely operated vehicles (ROVs) to collect mineral samples from prospective mine sites. Using drills and other cutting tools, the ROVs obtain samples to be analyzed for precious materials. Once a site has been located, a mining ship or station is set up to mine the area.

There are two predominant forms of mineral extraction being considered for full-scale operations: continuous-line bucket system (CLB) and the hydraulic suction system. The CLB system is the preferred method of nodule collection. It operates much like a conveyor-belt, running from the sea floor to the surface of the ocean where a ship or mining platform extracts the desired minerals, and returns the tailings to the ocean. Hydraulic suction mining lowers a pipe to the seafloor which transfers nodules up to the mining ship. Another pipe from the ship to the seafloor returns the tailings to the area of the mining site.

In recent years, the most promising mining areas have been the Central and Eastern Manus Basin around Papua New Guinea and the crater of Conical Seamount to the east. These locations have shown promising amounts of gold in the area's sulfide deposits (an average of 26 parts per million). The relatively shallow water depth of 1050 m, along with the close proximity of a gold processing plant makes for an excellent mining site.

Deep sea mining project value chain can be differentiated using the criteria of the type of activities where the value is actually added. During prospecting, exploration and resource assessment phases the value is added to intangible assets, for the extraction, processing and distribution phases the value increases with relation to product processing. There is an intermediate phase – the pilot mining test which could be considered to be an inevitable step in the shift from “resources” to “reserves” classification, where the actual value starts.Abramowski, T. (2016)
Value chain of deep seabed mining
, Article in the book: Deep sea mining value chain: organization, technology and development, pp 9-18, Interoceanmetal Joint Organization

Exploration phase involves such operations as locating, sea bottom scanning and sampling using technologies such as echo-sounders, side scan sonars, deep-towed photography, ROVs, AUVs. The resource valuation incorporates the examination of data in the context of potential mining feasibility.

Value chain based on product processing involves such operations as actual mining (or extraction), vertical transport, storing, offloading, transport, metallurgical processing for final products. Unlike the exploration phase, the value increases after each operation on processed material eventually delivered to the metal market. Logistics involves technologies analogous to those applied in land mines. This is also the case for the metallurgical processing, although rich and polymetallic mineral composition which distinguishes marine minerals from its land analogs requires special treatment of the deposit. Environmental monitoring and impact assessment analysis relate to the temporal and spatial discharges of the mining system if they occur, sediment plumes, disturbance to the benthic environment and the analysis of the regions affected by seafloor machines. The step involves an examination of disturbances near the seafloor, as well as disturbances near the surface. Observations include baseline comparisons for the sake of quantitative impact assessments for ensuring the sustainability of the mining process.

Small scale mining of the deep sea floor is being developed off the coast of Papua New Guinea using robotic techniques, but the obstacles are formidable.

Environmental impacts

As with all mining operations, deep sea mining raises questions about potential environmental damages to the surrounding areas. Because deep sea mining is a relatively new field, the complete consequences of full-scale mining operations are under investigation.

Newer technology which is being developed has the potential to avoid sediment plumes and use selective pick up technology. Selective pickup avoids picking up any nodules which contain life and can be programmed to leave behind a percentage of the nodules to maintain the habitat. This is not possible with dredging collector machines.

However, experts are certain that removal of parts of the sea floor will result in disturbances to the benthic layer, increased toxicity of the water column, and sediment plumes from tailings. Removing parts of the sea floor disturbs the habitat of benthic organisms