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Post Info TOPIC: Deep Sea Mining Geology


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Deep Sea Mining Geology

Deep Sea Mining

All of the minerals discussed previously have been recovered by surface mining on the shallow continental shelves or nearshore coasts. The metaliferous oxides and metaliferous sulfides occur in the deep ocean. Metaliferous oxides such as manganese nodules were collected by the HMS Challenger in 1872 and their potential has been dreamed about ever since, but deep ocean mining of these minerals is still in its infancy.

At depths between 4,000m and 6,000m, developing mining and processing technologies needed to recover the desired minerals from the nodules - nickel, copper, cobalt, and manganese - require large investments. One enterprise is now in an advanced stage of preparatory work for extracting hydrothermal metalliferous muds from the deep trenches of the Red Sea. Despite the rather dismal mineral market conditions, we will become more dependent on the oceans as a mineral resource reservoir in the future.

Metaliferous Oxides

In the early 60's John Mero's thesis demonstrated the economic potential of manganese nodules. This was followed by "nodule fever" with industrial companies investing millions of dollars in the development of mining and processing technology. In the 1960's, the competition for copper, nickel, and cobalt drove prices upward and many nonferrous metals were in short supply. Ferromanganese nodules (manganese nodules) and ferromanganese crusts (crusts) have a wide distribution and have in common a composition dominated by manganese and iron oxides.

Manganese nodules occur in all the oceans. Their accretion rate is very slow, only a few mm in 1 million years. The average nodule has 24% manganese, compared to 35 to 55% manganese in land ore bodies, so they do not offer solid economics as a manganese source, but they also contain iron (14%), copper (1%), nickel (1%), and cobalt (0.25%).

Cobalt enriched crusts on the flanks of seamounts, volcanic islands, and ridges contain as much as 2.5% cobalt and these occur in depths of 1000 to 2500 meters. Because the crusts are only about 2 cm thick, the mining technology presents a problem. Both the manganese nodules and crusts may be exploited in the future. Potential mining sites are a 500 mile wide nodule belt running for 2500 miles from west of Mexico to South of Hawaii, belts of North Pacific nodules that are close to Japanese and American markets, and a large concentration in the North Atlantic that is near American and European markets.

Cobalt is the most important of the elements in nodules and crusts in price and as a strategic metal. It is indispensable for "superalloys" used in jet aircraft engines. Cobalt supplies are limited, and the largest producer is Zaire. Ocean mining would provide a new source. Cobalt-rich manganese crusts occur on the shallower flanks of volcanic islands and seamounts. Thus, these deposits may be easily recovered compared to the deposits found in the deeper areas.

In the last 20 years, many nodule deposits have been located, mapped, and evaluated. Commercial interest have centered on the region of the eastern Pacific between the Clarion and Clipperton fracture zones. In 1984, the US Dept. Commerce issued exploration licenses to four consortia. But now a hiatus in activity that began in the mid 1980's is evident. Progress has slowed until advancement is nearly imperceptible. After the first oil embargo in metal markets were affected. Poorer nations not only ceased purchasing metals, but immediately increased ore production whenever possible. The life-style of affluent nations plunged and the metal market was depressed.

Problems associated with nodule mining include who owns the deposits, how to obtain mining claims, and environmental problems of collection and processing. Provisions written into the Law of the Sea were designed to handle nodule exploration, exploitation, distribution, and the sharing of profits. We still have no deep sea mining, and probably will not for some years, but the early interest led to drawing up the Law of the Sea to answer some of the questions hindering legal mining. Political stability and investment climate will be important driving factors. Many once active nodule mining technology research programs have been on hold since the early 1980s.

Nodule mining is sensitive to metal prices and to the required energy and capital costs involved in mining. Processing is the most costly phase of nodule production, with energy the paramount input. A cost-cutting approach is nodule benefaction on board shipboard by leaching (hydrometallurgy), roasting/smelting (pyrometallurgy), or combinations of the two. Because the main minerals (copper, nickel, cobalt, and manganese) contained in nodules are some of those most in demand by industry, extraction technology, and economic analyses have focused on them. Looming beyond the engineering difficulties, prospective producers face a currently depressed metal market. Cobalt's onshore "resource life expectancy" has been calculated at 340 years and world capacity to produce cobalt exceeds demand.

At the present, exploration ships are limited in number and no mining ship has been developed. It would be an enormous vessel, capable of operating non-stop for months at a time and scooping up millions of tons of nodules per year. Nodules would be transferred to bulk carriers, which would shuttle between mining ships and shore processing plants. The magnitude of costs and rewards are enormous -- the amount of metals produced from a single major operation could alter world prices. Production might equal 50% of the current consumption of manganese and 100% of the required cobalt.

The value of nodule-bearing areas differ widely; any location will have a value depending on metallic content, density of occurrence, depth of water, characteristics of the bottom, distance from shore. Development of these resources is restricted to developed nations because of the requirements of technology and capital.

The major fundamental issue remains that of technical and economic feasibility of nodule mining. Although there are trillions of tons of nodules in the oceans, the gathering or exploiting is a good deal more complicated than simply raising enough nodules to make a profit. One must raise enough high grade nodules to make a profit. This focuses attention on an important mining principle, the necessity of obtaining long term assured access to specific mining sites. Some observers unfamiliar with mining economics have suggested that mining companies simply fish for nodules, without obtaining concessions to a specific site. Because of the variability of manganese nodule metal content, the company must have exclusive access to high grade nodules and nodules that are consistent compositionally which is important for efficient processing.

Polymetallic Sulfide Deposits

Polymetallic sulfide deposits are products of the circulation of seawater through the hot volcanic rocks which well up along spreading ridges of the oceans and back-arc basins. Upon coming in contact with cooler water, the minerals precipitate producing mineral deposits of zinc, copper, lead, barium, silver, and gold in widely varying proportions in sulfides and oxides. Some deposits in heavily sedimented environments appear to contain several millions of tons of ore and compare with some of the largest massive sulfide deposits that are being mined on land. Except for the Atlantis II Deep in the Red Sea, none of the deposits have been surveyed and sampled sufficiently to determine their grade and tonnage.

Deposits are known from about 100 locations in the Pacific, two in the Atlantic, one in the Mediterranean, one in the Indian Ocean, and in several "deeps" of the Red Sea. Deposits at six sites (Atlantis II Deep, Escanaba Trough, Middle Valley, TAG, seamount at 13o N, and southern Explorer Ridge) are within the size range of deposits that would be mined on land under favorable economic conditions.

Many marine mineral specialists believe that some polymetallic sulphides will be extracted before mining ferromanganese crusts and nodules. Mining will focus on sediments of the Red Sea type. Where polymetallic sulphides occur as loosely consolidated sediments, they should be easier to exploit. The Red Sea sediments measure 10-20m deep within a 5-km-wide and 13-km-long area of about 56 million m2. The sediments contain an estimated 32 million tons of metal and are about 35m thick at the main mine site. Of this total, iron measures 29 percent, zinc 1.5 percent, copper 0.8 percent, and lead 0.1 percent. Mining activity will be dependent on an increase of the presently unfavorable metal prices, solving technical problems in recovery and processing and environmental problems and regulatory problems. The resource is substantial, but unfavorable metal prices and problems in recovery and processing make it unlikely that exploitation will begin soon.

Political and Legal Aspects

The most limiting factors associated with deep-sea marine mining are the political and legal aspects. Legal and political issues surrounding exploration, exploitation, and marketing of sea floor minerals must be resolved. Even waters within the sovereign rights of territorial seas present difficulties because of inequalities of operational laws, royalties, lease agreements, and political stability. Conflicts between user groups, especially nearshore, and concerns about pollution need to be resolved with a set of regulations controlling and defining activities. Even where coastal zone management programs are in effect, resolving conflicts can still be a long process. We need to develop new efficient techniques of mining which are environmentally clean.

Three United Nations Conferences on Law of the Sea were held. The first, the 1958 Geneva Convention produced a treaty stating that consent of coastal state shall be obtained in respect to any research concerning the continental shelf, and also the coastal state exercises sovereign right over the continental shelf for the purpose of exploring and exploiting resources. The 1982 convention proposed the Law of the Sea, which defines specific rights for international and territorial waters. The Law of the Sea treaty (LOS) was signed by a total of 138 nations.

The main dispute about the LOS treaty is the legislation on deep sea mining. The law states that if a company or government wants to mine within a given area it should take out a license to mine it. The company should mine one part of the area for itself and the other part for the United Nations. Also the company should transfer its technology to other nations. The operating climate for U.S. mining activities embodied in this treaty led to refusal of the U.S. to join. The third conference in 1992 established seaward boundaries and more explicit rules on mining development that controlled pre-exploitation surveys or prospecting.

As coastal states become sensitive to mineral exploitation, they are reluctant to permit foreign scientists to work there -- but unless research is done, neither the resources or associated environmental factors are likely to be revealed. Commercial development of ocean minerals will not become reality until scientific, engineering, legal, and social needs are met.

For the U.S., development of environmental regulations and awarding of mineral claims rests with the Office of Ocean Minerals and Energy, a part of NOAA. Although the United States has not signed the LOS treaty, it has accepted part five of the treaty which proclaims an Exclusive Economic Zone (EEZ). In 1983, President Reagan declared a 200 nautical mile Exclusive Economic Zone for the United States and its possessions. This has allowed the United States to have rights over 4.9 billion acres of ocean, including areas such as Puerto Rico, the Northern Mariana Islands, Guam, American Samoa, Johnston Island, Jarvis Island, and The U.S. Virgin Islands.

The EEZ concept solves many problems politically and socially, but it also creates a great many problems. For example: who is the enforcer the this zone, what about navigation through these zones, and what happens if two nations boundaries overlap. All of these problems have limited the amount of marine mining being done at the present time. Manganese nodule recovery is low due to the controversies of the LOS treaty. Oil discoveries and subsequent production has decreased due to legal and political problems. Industries are not going to invest money into areas that may become problematic, and governments will not fund such risky projects. This causes a decrease in research and development. Also the increased problems may increase the cost thus making onshore mining much more profitable than going offshore.

Pollution from a land-based mining operation may be confined to a local area, and resolved locally. Those instances where pollution from mining or refining cause river pollution or atmospheric pollution that can travel to neighboring political states, create situations difficult to resolve. The waters overlying marine resources freely spread any pollution and the environmental problems cross political boundaries unless the operation is very small and local. Use of the oceans will be similar for the next decade --more oil and gas, more transportation, more recreation -- and with this, more pollution, more congestion, more conflict and controversy, more depletion and more economic waste.



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