14. Mineral resources of the World Ocean
The oceans, which occupy about 71% of the surface of our planet, are also a huge storehouse of mineral wealth. Mineral resources within its limits are enclosed in two different environments - in fact, in the oceanic water mass, as the main part of the hydrosphere, and in the underlying earth's crust, as part of the lithosphere. According to the state of aggregation and, accordingly, the operating conditions, they are divided into: 1) liquid, gaseous and dissolved, exploration and production of which is possible with the help of boreholes (oil, natural gas, salt, sulfur, etc.); 2) hard surface, the operation of which is possible with the help of dredges, hydraulic and other similar methods (metal-bearing placers and silts, nodules, etc.); 3) solid buried, the exploitation of which is possible by mine methods (coal, iron and some other ores).
The division of the mineral resources of the World Ocean into two large classes is also widely used: hydrochemical and geological resources. Hydrochemical resources include seawater itself, which can also be considered as a solution containing many chemical compounds and trace elements. The geological include those mineral resources that are in the surface layer and the bowels of the earth's crust.
The hydrochemical resources of the World Ocean are elements of the salt composition of ocean and sea waters that can be used for economic needs. According to modern estimates, such waters contain about 80 chemical elements, the diversity of which is shown in Figure 10. The oceanosphere contains the largest amount of compounds of chlorine, sodium, magnesium, sulfur, calcium, the concentration of which (in mg / l) is quite high; this group includes hydrogen and oxygen. The concentration of most other chemical elements is much lower, and sometimes scanty (for example, the content of silver is 0.0003 mg / l, tin is 0.0008, gold is 0.00001, lead is 0.00003, and tantalum is 0.000003 mg / l), therefore seawater is called "lean ore". However, with its overall huge volume, the total amount of some hydrochemical resources may turn out to be quite significant.
It is estimated that 1 km 3 of seawater contains 35–37 million tons of dissolved substances. Including about 20 million tons of chlorine compounds, 9.5 million tons of magnesium, 6.2 million tons of sulfur, as well as about 30 thousand tons of bromine, 4 thousand tons of aluminum, 3 thousand tons of copper. Another 80 tons are manganese, 0.3 tons - silver and 0.04 tons - gold. In addition, 1 km 3 of sea water contains a lot of oxygen and hydrogen, there is also carbon and nitrogen.
All this creates the basis for the development of the "marine" chemical industry.
The geological resources of the World Ocean are the resources of mineral raw materials and fuels that are no longer contained in the hydrosphere, but in the lithosphere, that is, associated with the ocean floor. They can be subdivided into shelf, continental slope, and deep seafloor resources. The main role among them is played by the resources of the continental shelf, covering an area of 31.2 million km 2, or 8.6% of the total ocean area.
Rice. ten. Hydrochemical resources of the oceanosphere (according to R.A. Kryzhanovsky)
The most famous and valuable mineral resource of the World Ocean is hydrocarbons: oil and natural gas. Even according to data at the end of the 80s. XX century, 330 sedimentary basins, promising for oil and gas, were explored in the World Ocean. In about 100 of them, about 2,000 fields were discovered. Most of these basins are continuation of land basins and are folded geosynclinal structures, but there are also purely marine sedimentary oil and gas basins that do not go beyond their water areas. According to some estimates, the total area of such basins within the World Ocean reaches 60–80 million km 2. As for their reserves, they are estimated differently in different sources: for oil - from 80 billion to 120–150 billion tons, and for gas - from 40–50 trillion cubic meters to 150 trillion cubic meters. Approximately 2/3 of these reserves belong to the Atlantic Ocean.
When characterizing the oil and gas resources of the World Ocean, they usually primarily mean the most accessible resources of its shelf. The largest oil and gas basins on the Atlantic Ocean shelf are explored off the coast of Europe (North Sea), Africa (Guinea), Central America (Caribbean), smaller ones - off the coast of Canada and the USA, Brazil, in the Mediterranean and some other seas. In the Pacific Ocean, such basins are known off the coasts of Asia, North and South America, and Australia. In the Indian Ocean, the Persian Gulf holds the leading place in reserves, but oil and gas have also been found on the shelf of India, Indonesia, Australia, and in the Arctic Ocean - off the coast of Alaska and Canada (Beaufort Sea) and off the coast of Russia (Barents and Kara Seas) ... The Caspian Sea should be added to this list.
However, the continental shelf accounts for only about 1/3 of the predicted oil and gas resources in the World Ocean. The rest of them belong to the sedimentary strata of the continental slope and deep-water basins located at a distance of many hundreds and even thousands of kilometers from the coast. The depth of occurrence of oil and gas reservoirs is much greater here. It reaches 500-1000 m and more. Scientists have established that the greatest prospects for oil and gas have deep-sea basins located: in the Atlantic Ocean - in the Caribbean Sea and off the coast of Argentina; in the Pacific Ocean - in the Bering Sea; in the Indian Ocean - off the coast
East Africa and the Bay of Bengal; in the Arctic Ocean - off the coast of Alaska and Canada, as well as off the coast of Antarctica.
In addition to oil and natural gas, solid mineral resources are associated with the shelf of the World Ocean. By the nature of their occurrence, they are subdivided into indigenous and placer.
The bedrock deposits of coal, iron, copper-nickel ores, tin, mercury, sodium chloride and potassium salts, sulfur and some other buried-type minerals are usually genetically associated with the deposits and basins of the adjacent parts of the land. They are known in many coastal regions of the World Ocean, and in some places they are developed with the help of mines and adits. (fig. 11).
Coastal-marine placers of heavy metals and minerals should be sought in the border zone of land and sea - on beaches and lagoons, and sometimes in a strip of ancient beaches flooded by the ocean.
Of the metals contained in such placers, the most important is the tin ore - cassiterite, which occurs in the coastal-marine placers of Malaysia, Indonesia and Thailand. Around the "tin islands" of this area, they can be traced at a distance of 10-15 km from the coast and to a depth of 35 m. Off the coast of Japan, Canada, New Zealand and some other countries, reserves of ferruginous (titanomagnetite and monazite) sands have been explored, off the coast of the USA and Canada - gold-bearing sands, off the coast of Australia - bauxite. Coastal-sea placers of heavy minerals are even more widespread. First of all, this applies to the coast of Australia (ilmenite, zircon, rutile, monazite), India and Sri Lanka (ilmenite, monazite, zircon), the USA (ilmenite, monazite), Brazil (monazite). Placer diamond deposits are known off the coast of Namibia and Angola.
Phosphorites occupy a somewhat special position in this list. Large deposits of them were found on the shelf of the western and eastern coasts of the United States, in the strip of the Atlantic coast of Africa, along the Pacific coast of South America. However, even Soviet oceanographic expeditions in the 60s – 70s. XX century phosphorites were explored not only on the shelf, but also within the continental slope and volcanic uplifts in the central parts of the oceans.
Of the other solid mineral resources, the most interesting are ferromanganese nodules, first discovered more than a hundred years ago by the British expeditionary ship Challenger. Since then they have been explored by oceanographic expeditions of many countries, including Soviet ones - on the ships Vityaz>, Akademik Kurchatov), Dmitry Mendeleev, etc. It was found that such nodules are found at depths from 100 to 7000 m , i.e., in the shelf seas, for example, the Kara, Barents, and within the deep-sea floor of the ocean and its depressions. At great depths, the deposits of nodules are much larger, so that these peculiar brown "potatoes" ranging in size from 2–5 to 10 cm form an almost continuous "pavement". Although nodules are called ferromanganese, since they contain 20% manganese and 15% iron, they also contain smaller amounts of nickel, cobalt, copper, titanium, molybdenum, rare earths and other valuable elements - more than 30 in total. Therefore, in fact, they are polymetallic ores ...
Rice. eleven. Mineral resources of the bottom of the World Ocean (according to V.D. and M.V. Voiloshnikov)
The total reserves of nodules in the World Ocean are estimated with a very large “fork”: from 2-3 trillion to 20 trillion tons, and the recoverable ones are usually up to 0.5 billion tons. It should also be taken into account that they grow by 10 million tons annually.
The main accumulations of nodules are located in the Pacific Ocean, where they occupy an area of 16 million km 2. It is customary to distinguish three main zones (hollows) there - northern, middle and southern. In some areas of these basins, the density of nodules reaches 70 kg per 1 m 2 (with an average of about 10 kg). In the Indian Ocean, nodules have also been explored in several deep-water basins, mainly in its central part, but their deposits in this ocean are much less than in the Pacific, and the quality is worse. There are even fewer nodules in the Atlantic Ocean, where their more or less extensive fields are located in the northwest, in the North American Basin, and off the coast of South Africa (rice. 77).
In addition to nodules, there are ferromanganese crusts on the ocean floor that cover rocks in the zones of the mid-ocean ridges. These crusts are often located at depths of 1–3 km. Interestingly, they contain much more manganese than ferromanganese nodules. They also contain ores of zinc, copper, and cobalt.
Russia, which has a very long coastline, also owns the most extensive continental shelf in terms of area (6.2 million km 2, or 20% of the world shelf, of which 4 million km 2 are promising for oil and gas). Large reserves of oil and gas have already been discovered on the shelf of the Arctic Ocean - primarily in the Barents and Kara Seas, as well as in the Sea of Okhotsk (off the coast of Sakhalin). According to some estimates, 2/5 of all potential natural gas resources are associated with the seas in Russia. In the coastal zone, placer deposits and carbonate deposits are also known, which are used to obtain building materials.
The treasures of sunken ships can also be considered as a kind of "resources" of the bottom of the World Ocean: according to the estimates of American oceanographers, at least 1 million of such ships lie at the bottom! Yes, and now they die annually from 300 to 400.
Most of the underwater treasures are located at the bottom of the Atlantic Ocean, through the expanses of which, in the era of the Great Geographical Discoveries, gold and silver were exported to Europe in large quantities. Dozens of ships were killed by hurricanes and storms. Recently, with the help of the most modern technology, the remains of Spanish galleons have been found on the ocean floor. Huge values were lifted from them.
In 1985, an American search team discovered the famous Titanic, sunk in 1912, in whose safes billions of dollars worth of valuables, including 26 thousand silver plates and trays, were buried, but they have not yet been able to lift them from a depth of more than 4 km.
One more example. During the Second World War, 465 gold bars (5.5 tons) were sent from Murmansk to England on the Edinburgh cruiser to pay for military supplies of the Allies. In the Barents Sea, the cruiser was attacked by a German submarine and damaged. It was decided to flood it so that the gold would not fall into the hands of the enemy. After 40 years, the divers descended to a depth of 260 m, where the ship sank, and all the gold bars were recovered and raised to the surface.
