Phosphorite

Phosphorite, phosphate rock or rock phosphate is a non-detrital sedimentary rock which contains high amounts of phosphate minerals. The phosphate content of phosphorite (or grade of phosphate rock) varies greatly, from 4%[1] to 20% phosphorus pentoxide (P2O5). Marketed phosphate rock is enriched ("beneficiated") to at least 28%, often more than 30% P2O5. This occurs through washing, screening, de-liming, magnetic separation or flotation.[1] By comparison, the average phosphorus content of sedimentary rocks is less than 0.2%.[2] The phosphate is present as fluorapatite Ca5(PO4)3F typically in cryptocrystalline masses (grain sizes < 1 μm) referred to as collophane-sedimentary apatite deposits of uncertain origin.[2] It is also present as hydroxyapatite Ca5(PO4)3OH or Ca10(PO4)6(OH)2, which is often dissolved from vertebrate bones and teeth, whereas fluorapatite can originate from hydrothermal veins. Other sources also include chemically dissolved phosphate minerals from igneous and metamorphic rocks. Phosphorite deposits often occur in extensive layers, which cumulatively cover tens of thousands of square kilometres of the Earth's crust.[3]

Limestones and mudstones are common phosphate-bearing rocks.[4] Phosphate rich sedimentary rocks can occur in dark brown to black beds, ranging from centimeter-sized laminae to beds that are several meters thick. Although these thick beds can exist, they are rarely only composed of phosphatic sedimentary rocks. Phosphatic sedimentary rocks are commonly accompanied by or interbedded with shales, cherts, limestone, dolomites and sometimes sandstone.[4] These layers contain the same textures and structures as fine-grained limestones and may represent diagenetic replacements of carbonate minerals by phosphates.[2] They also can be composed of peloids, ooids, fossils, and clasts that are made up of apatite. There are some phosphorites that are very small and have no distinctive granular textures. This means that their textures are similar to that of collophane, or fine micrite-like texture. Phosphatic grains may be accompanied by organic matter, clay minerals, silt sized detrital grains, and pyrite. Peloidal or pelletal phosphorites occur normally; whereas oolitic phosphorites are not common.[4]

Phosphorites are known from Proterozoic banded iron formations in Australia, but are more common from Paleozoic and Cenozoic sediments. The Permian Phosphoria Formation of the western United States represents some 15 million years of sedimentation. It reaches a thickness of 420 metres and covers an area of 350,000 km2.[2] Commercially mined phosphorites occur in France, Belgium, Spain, Morocco, Tunisia and Algeria. In the United States phosphorites have been mined in Florida, Tennessee, Wyoming, Utah, Idaho and Kansas.[5]

Peloidal phosphorite Phosphoria Formation Simplot Mine Idaho
Peloidal phosphorite, Phosphoria Formation, Simplot Mine, Idaho. 4.6 cm wide.
Fossiliferous peloidal phosphorite, Yunnan Province China
Fossiliferous peloidal phosphorite, (4.7 cm across), Yunnan Province, China.

Classification of phosphatic sedimentary rocks

(1) Pristine: Phosphates that are in pristine conditions have not undergone bioturbation. In other words, the word pristine is used when phosphatic sediment, phosphatized stromatolites and phosphate hardgrounds have not been disturbed.[6]

(2) Condensed: Phosphatic particles, laminae and beds are considered condensed when they have been concentrated. This is helped by the extracting and reworking processes of phosphatic particles or bioturbation.[6]

(3) Allochthonous: Phosphatic particles that were moved by turbulent or gravity-driven flows and deposited by these flows.[6]

Phosphorus cycle, formation and accumulation

The heaviest accumulation of phosphorus is mainly on the ocean floor. Phosphorus accumulation occurs from atmospheric precipitation, dust, glacial runoff, cosmic activity, underground hydrothermal volcanic activity, and deposition of organic material. The primary inflow of dissolved phosphorus is from continental weathering, brought out by rivers to the ocean.[7] It is then processed by both micro- and macro-organisms. Diatomaceous plankton, phytoplankton, and zooplankton process and dissolve phosphorus in the water. The bones and teeth of certain fish (e.g. anchovies) absorb phosphorus and are later deposited and buried in the ocean sediment.[8]

Depending on the pH and salinity levels of the ocean water, organic matter will decay and releases phosphorus from sediment in shallow basins. Bacteria and enzymes dissolve organic matter on the water bottom interface, thus returning phosphorus to the beginning of its biogenic cycle. Mineralization of organic matter can also cause the release of phosphorus back into the ocean water.[7]

Depositional environments

Phosphates are known to be deposited in a wide range of depositional environments. Normally phosphates are deposited in very shallow, near-shore marine or low energy environments. This includes environments such as supratidal zones, littoral or intertidal zones, and most importantly estuarine.[8] Currently, areas of oceanic upwelling cause the formation of phosphates. This is because of the constant stream of phosphate brought from the large, deep ocean reservoir (see below). This cycle allows continuous growth of organisms.[6]

Supratidal zones: Supratidal environments are part of the tidal flat system where the presence of strong wave activity is non-existent. Tidal flat systems are created along open coasts and relatively low wave energy environments. They can also develop on high energy coasts behind barrier islands where they are sheltered from the high energy wave action. Within the tidal flat system, the supratidal zone lies in a very high tide level. However, it can be flooded by extreme tides and cut across by tidal channels. This is also subaerially exposed, but is flooded twice a month by spring tides.[9]

Littoral environments/ intertidal zones: Intertidal zones are also part of the tidal flat system. The intertidal zone is located within the mean high and low tide levels. It is subject to tidal shifts, which means that it is subaerially exposed once or twice a day. It is not exposed long enough to withhold vegetation. The zone contains both suspension sedimentation and bed load.[9]

Estuarine environments: Estuarine environments, or estuaries, are located at the lower parts of rivers that flow into the open sea. Since they are in the seaward section of the drowned valley system they receive sediment from both marine and fluvial sources. These contain facies that are affected by tide and wave fluvial processes. An estuary is considered to stretch from the landward limit of tidal facies to the seaward limit of coastal facies. Phosphorites are often deposited in fjords within estuarine environments. These are estuaries with shallow sill constrictions. During Holocene sea-level rise, fjord estuaries formed by drowning of glacially-eroded U-shaped valleys.[9]

The most common occurrence of phosphorites is related to strong marine upwelling of sediments. Upwelling is caused by deep water currents that are brought up to coastal surfaces where a large deposition of phosphorites may occur. This type of environment is the main reason why phosphorites are commonly associated with silica and chert. Estuaries are also known as a phosphorus “trap”. This is because coastal estuaries contain a high productivity of phosphorus from marsh grass and benthic algae which allow an equilibrium exchange between living and dead organisms.[10]

Types of phosphorite deposition

  • Phosphate nodules: These are spherical concentrations that are randomly distributed along the floor of continental shelves. Most phosphorite grains are sand size although particles greater than 2 mm may be present. These larger grains, referred to as nodules, can range up to several tens of centimeters in size.
  • Bioclastic phosphates or bone beds: Bone beds are bedded phosphate deposits that contain concentrations of small skeletal particles and coprolites.[4] Some also contain invertebrate fossils like brachiopods and become more enriched in P2O5 after diagentic processes have occurred. Bioclastic phosphates can also be cemented by phosphate minerals.[7]
  • Phosphatization: Phosphatization is a type of rare diagenetic processes. It occurs when fluids that are rich in phosphate are leached from guano.[4] These are then concentrated and reprecipitated in limestone. Phosphatized fossils or fragments of original phosphatic shells are important components within some these deposits.

Tectonic and oceanographic settings of marine phosphorites

  • Epeiric sea phosphorites: Epeiric sea phosphorites are within marine shelf environments. These are in a broad and shallow cratonic setting. This is where granular phosphorites, phosphorite hardgrounds, and nodules occur.[6]
  • Continental margin phosphorites: Convergent, passive, upwelling, non-upwelling. This environment accumulates phosphorites in the form of hardgrounds, nodules and granular beds.[10] These accumulate by carbonate fluorapatite percipitaion during early diagenesis in the upper few tens of centimeters of sediment. There are two different environmental conditions in which phosphorites are produced within continental margins. Continental margins can consist of organic rich sedimentation, strong coastal upwelling, and pronounced low oxygen zones. They can also form in conditions such as oxygen rich bottom waters and organic poor sediments.[6]
  • Seamount phosphorites: These are phosphorites that occur in seamounts, guyots, or flat topped seamounts, seamount ridges. These phosphorites are produced in association with iron and magnesium bearing crusts. In this setting the productivity of phosphorus is recycled within an iron oxidation reduction phosphorus cycle. This cycle can also form glauconite which is normally associated with modern and ancient phosphorites.[6]
  • Insular phosphorites: Insular phosphorites are located in carbonate islands, plateaus, coral island consisting of a reef surrounding a lagoon or, atoll lagoon, marine lakes. The phosphorite here originates from guano. Replacement of deep sea sediments precipitates, that has been formed in place on the ocean floor.[6]

Production and use

DSCN5766-guano-glantz crop b
Guano phosphorite mining in the Chincha Islands of Peru, c. 1860
Phosphorite Mine Oron Israel 070313
Phosphorite mine near Oron, Negev, Israel.

Production

Deposits which contain phosphate in quantity and concentration which are economic to mine as ore for their phosphate content are not particularly common. The two main sources for phosphate are guano, formed from bird droppings, and rocks containing concentrations of the calcium phosphate mineral, apatite.

As of 2006, the US is the world's leading producer and exporter of phosphate fertilizers, accounting for about 37% of world P2O5 exports.[11] As of 2008, the world's total economic demonstrated resource of rock phosphate is 18 gigatonnes, which occurs principally as sedimentary marine phosphorites.[12]

As of 2012, China, the United States and Morocco are the world's largest miners of phosphate rock, with a production of 77 megatonnes, 29.4 Mt and 26.8 Mt (including 2.5 Mt in the Sahara of Morocco) respectively in 2012 while global production reached 195 Mt.[13] It is thought that in India there are almost 260 million tons of rock phosphate.[14] Other countries with significant production include Brazil, Russia, Jordan and Tunisia. Historically, large amounts of phosphates were obtained from deposits on small islands such as Christmas Island and Nauru, but these sources are now largely depleted.

Phosphate ore is mined and beneficiated into rock phosphate. Beneficiation of phosphate ore is a process which includes washing, flotation and calcining.[1] Froth flotation is used to concentrate the mined ore to rock phosphate. The mined ore is crushed and washed, creating a slurry, this ore slurry is then treated with fatty acids to cause calcium phosphate to become hydrophobic.

This rock phosphate is then either solubilized to produce wet-process phosphoric acid, or smelted to produce elemental phosphorus. Phosphoric acid is reacted with phosphate rock to produce the fertilizer triple superphosphate or with anhydrous ammonia to produce the ammonium phosphate fertilizers. Elemental phosphorus is the base for furnace-grade phosphoric acid, phosphorus pentasulfide, phosphorus pentoxide, and phosphorus trichloride.

Uses

Approximately 90% of rock phosphate production is used for fertilizer and animal feed supplements and the balance for industrial chemicals.[1] In addition to phosphate fertilisers for agriculture, phosphorus from rock phosphate is also used in animal feed supplements, food preservatives, anti-corrosion agents, cosmetics, fungicides, ceramics, water treatment and metallurgy.[12]

For use in the chemical fertilizer industry, beneficiated rock phosphate must be concentrated to levels of at least 28% phosphorus pentoxide (P2O5), although most marketed grades of phosphate rock are 30% or more.[1]

It must also have reasonable amounts of calcium carbonate (5%), and <4% combined iron and aluminium oxides. Worldwide, the resources of high-grade ore are declining, and use of lower grade ore may become more attractive.[1]

Beneficiated rock phosphate is also marketed and accepted as an "organic" alternative to "chemical" phosphate fertilizer which has been further concentrated from it, because it is perceived as being more "natural". According to a report for the FAO, it can be more sustainable to apply rock phosphate as a fertilizer in certain soil types and countries, although it has many drawbacks. According to the report it may have higher sustainability compared to more concentrated fertilizers because of reduced manufacturing costs and the possibility of local procurement of the refined ore.[1]

See also

References

  1. ^ a b c d e f g Zapata, F.; Roy, R.N. (2004). "Chapter 1 - Introduction: Phosphorus in the soil-plant system". Use of Phosphate Rocks for Sustainable Agriculture. Rome: Food and Agriculture Organization. ISBN 92-5-105030-9.
  2. ^ a b c d Blatt, Harvey and Robert J. Tracy, Petrology, Freeman, 1996, 2nd ed. pp. 345–349 ISBN 0-7167-2438-3
  3. ^ C.Michael Hogan. 2011. Phosphate. Encyclopedia of Earth. Topic ed. Andy Jorgensen. Ed.-in-Chief C.J.Cleveland. National Council for Science and the Environment. Washington DC
  4. ^ a b c d e Prothero, Donald R.; Schwab, Fred (22 August 2003). Sedimentary Geology. Macmillan. pp. 265–269. ISBN 978-0-7167-3905-0. Retrieved 15 December 2012.
  5. ^ Klein, Cornelis and Cornelius S. Hurlbut, Jr., Manual of Mineralogy, Wiley, 1985, 20th ed., p. 360, ISBN 0-471-80580-7
  6. ^ a b c d e f g h Middleton V. Gerald, 2003 Encyclopedia of Earth Sciences series. Encyclopedia of Sediment and Sedimentary Rocks. Kluwer Academic Publishers. Dordrect, Boston, London. pp 131, 727, 519–524.
  7. ^ a b c Filippelli, G.M., 2008. The global phosphorus cycle: Past, present and Future. Elements, 4(2): 89-95, doi=10.2113/GSELEMENTS.4.2.89.
  8. ^ a b Filippelli, G.M., 2011. Phosphate rock formation and marine phosphorus geochemistry: The deep time perspective. Chemosphere, doi:10.1016/j.chemosphere.2011.02.019.
  9. ^ a b c Boggs, Sam, Jr. (2006). Principles of Sedimentology and Stratigraphy (4th ed.), Pearson Education Inc., Upper Saddle River, NJ, pp. 217–223 ISBN 0321643186
  10. ^ a b Pevear, D. R. (1966). "The estuarine formation of United States Atlantic Coastal Plain phosphorite". Economic Geology. 61 (2): 251–256. doi:10.2113/gsecongeo.61.2.251.
  11. ^ US Geological Survey Minerals Yearbook 2006 Rock Phosphate
  12. ^ a b Phosphate AIMR Report 2008. ga.gov.au
  13. ^ IFA 2012 statistics
  14. ^ Cordell, Dana; White, Stuart (2013-01-31). "Sustainable Phosphorus Measures: Strategies and Technologies for Achieving Phosphorus Security". Agronomy. 3 (1): 86–116. doi:10.3390/agronomy3010086.

External links

1987 in the environment

This is a list of notable events relating to the environment in 1987. They relate to environmental law, conservation, environmentalism and environmental issues.

Apatite

Apatite is a group of phosphate minerals, usually referring to hydroxylapatite, fluorapatite and chlorapatite, with high concentrations of OH−, F− and Cl− ions, respectively, in the crystal. The formula of the admixture of the three most common endmembers is written as Ca10(PO4)6(OH,F,Cl)2, and the crystal unit cell formulae of the individual minerals are written as Ca10(PO4)6(OH)2, Ca10(PO4)6F2 and Ca10(PO4)6Cl2.

The mineral was named apatite by the German geologist Abraham Gottlob Werner in 1786, although the specific mineral he had described was reclassified as fluorapatite in 1860 by the German mineralogist Karl Friedrich August Rammelsberg. Apatite is often mistaken for other minerals. This tendency is reflected in the mineral's name, which is derived from the Greek word απατείν (apatein), which means to deceive or to be misleading.Apatite is one of a few minerals produced and used by biological micro-environmental systems. Apatite is the defining mineral for 5 on the Mohs scale. Hydroxyapatite, also known as hydroxylapatite, is the major component of tooth enamel and bone mineral. A relatively rare form of apatite in which most of the OH groups are absent and containing many carbonate and acid phosphate substitutions is a large component of bone material.

Fluorapatite (or fluoroapatite) is more resistant to acid attack than is hydroxyapatite; in the mid-20th century, it was discovered that communities whose water supply naturally contained fluorine had lower rates of dental caries. Fluoridated water allows exchange in the teeth of fluoride ions for hydroxyl groups in apatite. Similarly, toothpaste typically contains a source of fluoride anions (e.g. sodium fluoride, sodium monofluorophosphate). Too much fluoride results in dental fluorosis and/or skeletal fluorosis.

Fission tracks in apatite are commonly used to determine the thermal histories of orogenic (mountain) belts and of sediments in sedimentary basins. (U-Th)/He dating of apatite is also well established from noble gas diffusion studies for use in determining thermal histories and other, less typical applications such as paleo-wildfire dating.Phosphorite is a phosphate-rich sedimentary rock, that contains between 18% and 40% P2O5. The apatite in phosphorite is present as cryptocrystalline masses referred to as collophane.

Bone Valley Formation

The Bone Valley Formation is a geologic formation in Florida. It is sometimes classified as the upper member of the Peace River Formation of the Hawthorn Group. It contains economically important phosphorite deposits that are mined in west-central Florida, as well as rich assemblages of vertebrate fossils.

Fluorapatite

Fluorapatite, often with the alternate spelling of fluoroapatite, is a phosphate mineral with the formula Ca5(PO4)3F (calcium fluorophosphate). Fluorapatite is a hard crystalline solid. Although samples can have various color (green, brown, blue, yellow, violet, or colorless), the pure mineral is colorless as expected for a material lacking transition metals. Along with hydroxylapatite, it can be a component of tooth enamel.Fluorapatite crystallizes in a hexagonal crystal system. It is often combined as a solid solution with hydroxylapatite (Ca5(PO4)3OH or Ca10(PO4)6(OH)2) in biological matrices. Chlorapatite (Ca5(PO4)3Cl) is another related structure. Industrially, the mineral is an important source of both phosphoric and hydrofluoric acids.

Fluorapatite as a mineral is the most common phosphate mineral. It occurs widely as an accessory mineral in igneous rocks and in calcium rich metamorphic rocks. It commonly occurs as a detrital or diagenic mineral in sedimentary rocks and is an essential component of phosphorite ore deposits. It occurs as a residual mineral in lateritic soils.Fluorapatite is found in the teeth of sharks and other fishes in varying concentrations. It is also present in human teeth that have been exposed to fluoride ions, for example, through water fluoridation or by using fluoride-containing toothpaste. The presence of fluorapatite helps prevent tooth decay or dental caries. Fluoroapatite has a critical pH of 4.5, thus, it makes tooth structure more resistant to additional caries attack. It has a mild bacteriostatic property as well which helps in decreasing the proliferation of Streptococcus mutans, the predominant bacteria related to dental caries.

Geography of Belarus

Belarus, a landlocked, generally flat country (the average elevation is 162 meters (531 ft) above sea level) without natural borders, occupies an area of 207,600 square kilometers (80,200 sq mi), or slightly smaller than the United Kingdom or the state of Kansas. Its neighbors are Russia to the east and northeast, Latvia to the north, Lithuania to the northwest, Poland to the west, and Ukraine to the south. Its extension from north to south is 560 km (350 mi), from west to east is 650 km (400 mi).

Geology of Cambodia

The geology of Cambodia is the study of the nation's rocks, minerals, water and landforms. Cambodia's ancient geologic history in the Precambrian is poorly understood. The region experienced tectonic activity and low-grade metamorphic rock formation throughout the Paleozoic, which a shift to marine conditions and fossil formation during the Permian and through much of the Mesozoic. Few rocks remain from the Cenozoic. Cambodia has comparatively few natural resources, although there is bauxite formed from laterite weathering, as well as phosphorite, iron, gems, limestone and other materials.

Geology of Estonia

The geology of Estonia is the study of rocks, minerals, water, landforms and geologic history in Estonia. The crust is part of the East European Craton and formed beginning in the Paleoproterozoic nearly two billion years ago. Shallow marine environments predominated in Estonia, producing extensive natural resources from organic matter such as oil shale and phosphorite. The Mesozoic and much of the Cenozoic are not well-preserved in the rock record, although the glaciations during the Pleistocene buried deep valleys in sediment, rechanneled streams and left a landscape of extensive lakes and peat bogs.

Geology of Lithuania

The geology of Lithuania consists of ancient Proterozoic basement rock overlain by thick sequences of Paleozoic, Mesozoic and Cenozoic marine sedimentary rocks, with some oil reserves, abundant limestone, dolomite, phosphorite and glauconite. Lithuania is a country in the Baltic region of northern-eastern Europe.

Janatas

Janatas (Kazakh: Жаңатас, Jańatas, Russian: Жанатас) is a town in Sarysu District of Jambyl Region of southern Kazakhstan. It is located in the desert in the northwest of the region, at the border with South Kazakhstan Region. The name means "New stone" in Kazakh, referring to the newly found phosphorite deposits. Janatas serves as the administrative center of the district. Population: 20,731 (2009 Census results); 25,927 (1999 Census results).

Lomilik

Lomilik is a seamount in the Western Pacific Ocean, within the exclusive economic zone of the Marshall Islands. It lies to the west of Anewetak atoll and is named after the best fishing site of Anewetak atoll.Lomilik has a 40-by-15-kilometre-wide (24.9 mi × 9.3 mi) summit terrace with the proper summit at circa 1,500 metres (4,900 ft) depth; a scarp separates the two and small hills reach depths of 1,350 metres (4,430 ft). The summit terrace is covered by rocks with ooze in between. A notch in the southern flank of Lomilik was probably created by a landslide. It is part of the Magellan Seamounts and consists of a Cretaceous volcano with a thin layer of carbonate rocks and ferromanganese. Lami seamount lies northwest of Lomilik.The rocks found on Lomilik consist of basalt and limestone. Fluorapatite, hyaloclastite, mudstone, phosphorite and siltstone have been identified in rocks from the seamount. Manganese nodules have been found on Lomilik and the manganese crusts on the seamount reach thicknesses of over 10 centimetres (3.9 in); the thickest crust recovered from an ocean is a 18 centimetres (7.1 in) thick ferromanganese crust from Lomilik recovered in 1989. The deposits on Lomilik could potentially be mined.

Navoi Mining and Metallurgy Combinat

NMMC (English: State-Owned Enterprise Navoi Mining & Metallurgy Combine, Russian: Государственное предприятие «Навоийский горно-металлургический комбинат») is one of the largest Uzbek companies involved in the mining industry being among the top ten largest uranium and gold producers in the world. The most important ore deposits of the company are located in the Kyzyl Kum Desert.

Nodule (geology)

In sedimentology and geology, a nodule is small, irregularly rounded knot, mass, or lump of a mineral or mineral aggregate that typically has a contrasting composition, such as a pyrite nodule in coal, a chert nodule in limestone, or a phosphorite nodule in marine shale, from the enclosing sediment or sedimentary rock. Normally, a nodule has a warty or knobby surface and exists as a discrete mass within the host strata. In general, they lack any internal structure except for the preserved remnants of original bedding or fossils. Nodules are closely related to concretions and sometimes these terms are used interchangeably. Minerals that typically form nodules include calcite, chert, apatite (phosphorite), anhydrite, and pyrite.In sedimentology and geology, nodular is used to describe a sediment or sedimentary rock composed of scattered to loosely packed nodules in matrix of like or unlike character. It is also used to describe mineral aggregates that occur in the form of nodules, e.g. colloform mineral aggregate with a bulbed surface.Nodule is also used for widely scattered concretionary lumps of manganese, cobalt, iron, and nickel found on the floors of the world's oceans. This is especially true of manganese nodules. Manganese and phosphorite nodules form on the seafloor and are syndepositional in origin. Thus, technically speaking, they are concretions instead of nodules.Chert and flint nodules are often found in beds of limestone and chalk. They form from the redeposition of amorphous silica arising from the dissolution of siliceous spicules of sponges, or debris from radiolaria and the postdepositional replacement of either the enclosing limestone or chalk by this silica.

Phosphate mining in the United States

In 2015, 27.6 million metric tons of marketable phosphate rock, or phosphorite, was mined in the United States, making the US the world's third-largest producer, after China and Morocco. The phosphate mining industry employed 2,200 people. The value of phosphate rock mined was US$2.2 billion.

As of 2015, there are 10 active phosphate mines in four states: Florida, North Carolina, Idaho, and Utah. The eastern phosphate deposits are mined from open pits. The western deposits are mined from both surface and underground mines.

The exact phosphate content of the phosphate rock mined in 2015 is not available, but in the latest five-year period for which ore grades are available, 2009-2013, the grade of US phosphate rock varied from 28.5 to 29.0 percent P2O5.

As of 2016, remaining reserves of phosphate rock in the United States totaled 1.1 billion metric tons.

Phosphoria Formation

The Phosphoria Formation of the western United States is a geological formation of Early Permian age. It represents some 15 million years of sedimentation, reaches a thickness of 420 metres (1,380 ft) and covers an area of 350,000 square kilometres (140,000 sq mi).The Phosphoria includes phosphorite beds that are an important source of phosphorus. Many of its shales are rich in organic matter and are petroleum source rocks, and some of its dolomites include petroleum reservoirs.

Phosphorite War

The Phosphorite War (Estonian: Fosforiidisõda) is the name given to a late-1980s environmental campaign in the then-Estonian Soviet Socialist Republic, against the opening of large phosphorite mines in the Virumaa region. The movement, peaking in 1987, was successful in achieving its immediate goals, but also in encouraging and strengthening the nationalist movement which led to the restoration of Estonian independence in 1991. In Estonia it is regarded as a catalyst that led to the destabilization and dissolution of the Soviet regime.The campaign focused on two major issues. The large-scale environmental degradation that the new mines would cause was the most common subject in the public discussion. The other, more covert issue was the fear that the new mines' need for a workforce would start a wave of migration, bringing tens of thousands of workers from other parts of the Soviet Union to Estonia. In the view of Estonians this would have greatly worsened the already fragile demographic balance (the share of Estonians in Estonia dropped from about 97% immediately after World War II to 61.5% in 1989).

Rebala, Estonia

Rebala is a village in Jõelähtme Parish, Harju County in northern Estonia.

Rebala is famous for its Rebala Heritage Reserve. It covers around 70 square kilometres and contains more than 300 archaeological remains including stone-cist graves and cup-marked stones from the Bronze and Iron Ages.Rebala also has a medieval stone chapel, a church, and a large number of old farm buildings dating to the 18th/19th centuries. Rebala was one of the first areas in Estonia where was phosphorite was mined, beginning in the 1920s. During the Soviet era the main activity in the area was farming, but the 21st century has seen new housing developments due to the village's close proximity to the capital city, Tallinn.Tallinn Landfill (or Jõelähtme Landill) is located in Rebala.

South Lodge Pit

South Lodge Pit is a 0.5 hectare geological Site of Special Scientific Interest in Taplow in Buckinghamshire. It is a Geological Conservation Review site.This former chalk quarry dates to the late Cretaceous, around 83 million year ago. It is the only British example of a chalk phosphorite deposit, comparable to deposits in the Paris Basin. In the late Cretaceous sea levels were much higher and covered much of England, including Buckinghamshire. Marine fossils are found in several horizons, including annelids, oysters and bivalves.The site is on private land with no public access.

Tartu Students' Nature Conservation Circle

Tartu Students' Nature Conservation Circle is a nature conservation organization (society) at the University of Tartu.

Established in 1958, it is the oldest student nature conservation society in the world.It has been continuously active since then. As preparing the environmental activists of the country, it had a remarkable role in the Phosphorite War that influenced the destabilization and destruction of the Soviet Union in the end of 1980s.

Uranium ore

Uranium ore deposits are economically recoverable concentrations of uranium within the Earth's crust. Uranium is one of the more common elements in the Earth's crust, being 40 times more common than silver and 500 times more common than gold. It can be found almost everywhere in rock, soil, rivers, and oceans. The challenge for commercial uranium extraction is to find those areas where the concentrations are adequate to form an economically viable deposit. The primary use for uranium obtained from mining is in fuel for nuclear reactors.

Globally, the distribution of uranium ore deposits is widespread on all continents, with the largest deposits found in Australia, Kazakhstan, and Canada. To date, high-grade deposits are only found in the Athabasca Basin region of Canada.

Uranium deposits are generally classified based on host rocks, structural setting, and mineralogy of the deposit. The most widely used classification scheme was developed by the International Atomic Energy Agency (IAEA) and subdivides deposits into 15 categories.

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