Phosphorite, phosphate rock or rock phosphate is a non-detrital sedimentary rock that 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, Saudi Arabia [5] and Algeria. In the United States phosphorites have been mined in Florida, Tennessee, Wyoming, Utah, Idaho and Kansas. [6]
(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. [7]
(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. [7]
(3) Allochthonous: Phosphatic particles that were moved by turbulent or gravity-driven flows and deposited by these flows. [7]
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. [8] 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 marine sediment. [9]
Depending on the pH and salinity levels of the ocean water, organic matter will decay, releasing 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. [9]
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. [9] 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. [7]
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. [10]
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 support the growth of most vegetation. The zone contains both suspension sedimentation and bed load. [10]
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. [10]
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. [11]
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 or bat droppings, and rocks containing concentrations of the calcium phosphate mineral, apatite.
As of 2006 [update] , the US is the world's leading producer and exporter of phosphate fertilizers, accounting for about 37% of world P2O5 exports. [13] As of December 2018 [update] , the world's total economic demonstrated resource of rock phosphate is 70 gigatonnes, [14] which occurs principally as sedimentary marine phosphorites. [15]
As of 2012 [update] , 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. [16] It is thought that in India there are almost 260 million tons of rock phosphate. [17] 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.[ citation needed ]
Approximately 90% of rock phosphate production is used for fertilizer and animal feed supplements and the balance for industrial chemicals. [1] In addition, phosphorus from rock phosphate is also used in food preservatives, baking flour, pharmaceuticals, anticorrosion agents, cosmetics, fungicides, insecticides, detergents, ceramics, water treatment and metallurgy. [15]
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.[ citation needed ] 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]
Rare earth elements are being found within phosphorites. With increasing demand from modern technology a different method of finding rare earth elements, independent of China, is becoming increasingly important. With yields greater than those from deposits in China, phosphorites offer a new resource located within the U.S. that would likely lead to independence from influence of countries outside of the U.S. [18]
In chemistry, a phosphate is an anion, salt, functional group or ester derived from a phosphoric acid. It most commonly means orthophosphate, a derivative of orthophosphoric acid, a.k.a. phosphoric acid H3PO4.
Sedimentary rocks are types of rock that are formed by the accumulation or deposition of mineral or organic particles at Earth's surface, followed by cementation. Sedimentation is the collective name for processes that cause these particles to settle in place. The particles that form a sedimentary rock are called sediment, and may be composed of geological detritus (minerals) or biological detritus. The geological detritus originated from weathering and erosion of existing rocks, or from the solidification of molten lava blobs erupted by volcanoes. The geological detritus is transported to the place of deposition by water, wind, ice or mass movement, which are called agents of denudation. Biological detritus was formed by bodies and parts of dead aquatic organisms, as well as their fecal mass, suspended in water and slowly piling up on the floor of water bodies. Sedimentation may also occur as dissolved minerals precipitate from water solution.
Chert is a hard, fine-grained sedimentary rock composed of microcrystalline or cryptocrystalline quartz, the mineral form of silicon dioxide (SiO2). Chert is characteristically of biological origin, but may also occur inorganically as a chemical precipitate or a diagenetic replacement, as in petrified wood.
Coos Bay is an estuary where the Coos River enters the Pacific Ocean, the estuary is approximately 12 miles long and up to two miles wide. It is the largest estuary completely within Oregon state lines. The Coos Bay watershed covers an area of about 600 square miles and is located in northern Coos County, Oregon, in the United States. The Coos River, which begins in the Oregon Coast Range, enters the bay from the east. From Coos River, the bay forms a sharp loop northward before arching back to the south and out to the Pacific Ocean. Haynes Inlet enters the top of this loop. South Slough branches off from the bay directly before its entrance into the Pacific Ocean. The bay was formed when sea levels rose over 20,000 years ago at the end of the Last Glacial Maximum, flooding the mouth of the Coos River. Coos Bay is Oregon's most important coastal industrial center and international shipping port, with close ties to San Francisco, the Columbia River, Puget Sound and other major ports of the Pacific rim.
Mudrocks are a class of fine-grained siliciclastic sedimentary rocks. The varying types of mudrocks include siltstone, claystone, mudstone and shale. Most of the particles of which the stone is composed are less than 1⁄16 mm and are too small to study readily in the field. At first sight, the rock types appear quite similar; however, there are important differences in composition and nomenclature.
Various theories of ore genesis explain how the various types of mineral deposits form within Earth's crust. Ore-genesis theories vary depending on the mineral or commodity examined.
Agrogeology is the study of the origins of minerals known as agrominerals and their applications. These minerals are of importance to farming and horticulture, especially with regard to soil fertility and fertilizer components. These minerals are usually essential plant nutrients. Agrogeology can also be defined as the application of geology to problems in agriculture, particularly in reference to soil productivity and health. This field is a combination of a few different fields, including geology, soil science, agronomy, and chemistry. The overall objective is to advance agricultural production by using geological resources to improve chemical and physical aspects of soil.
Clastic rocks are composed of fragments, or clasts, of pre-existing minerals and rock. A clast is a fragment of geological detritus, chunks, and smaller grains of rock broken off other rocks by physical weathering. Geologists use the term clastic to refer to sedimentary rocks and particles in sediment transport, whether in suspension or as bed load, and in sediment deposits.
A carbonate platform is a sedimentary body which possesses topographic relief, and is composed of autochthonic calcareous deposits. Platform growth is mediated by sessile organisms whose skeletons build up the reef or by organisms which induce carbonate precipitation through their metabolism. Therefore, carbonate platforms can not grow up everywhere: they are not present in places where limiting factors to the life of reef-building organisms exist. Such limiting factors are, among others: light, water temperature, transparency and pH-Value. For example, carbonate sedimentation along the Atlantic South American coasts takes place everywhere but at the mouth of the Amazon River, because of the intense turbidity of the water there. Spectacular examples of present-day carbonate platforms are the Bahama Banks under which the platform is roughly 8 km thick, the Yucatan Peninsula which is up to 2 km thick, the Florida platform, the platform on which the Great Barrier Reef is growing, and the Maldive atolls. All these carbonate platforms and their associated reefs are confined to tropical latitudes. Today's reefs are built mainly by scleractinian corals, but in the distant past other organisms, like archaeocyatha or extinct cnidaria were important reef builders.
Yaquina Bay is a coastal estuarine community found in Newport, Oregon. Yaquina Bay is a semi-enclosed body of water, approximately 8 km2 (3.2 mi2) in area, with free connection to the Pacific Ocean, but also diluted with freshwater from the Yaquina River land drainage. The Bay is traversed by the Yaquina Bay Bridge.
In geology and particularly in sedimentology, a nodule is a small, irregularly rounded knot, mass, or lump of a mineral or mineral aggregate that typically has a contrasting composition from the enclosing sediment or sedimentary rock. Examples include pyrite nodules in coal, a chert nodule in limestone, or a phosphorite nodule in marine shale. 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.
Cyclic sediments are sequences of sedimentary rocks that are characterised by repetitive patterns of different rock types (strata) or facies within the sequence. Processes that generate sedimentary cyclicity can be either autocyclic or allocyclic, and can result in piles of sedimentary cycles hundreds or even thousands of metres thick. The study of sequence stratigraphy was developed from controversies over the causes of cyclic sedimentation.
The phosphorus cycle is the biogeochemical cycle that involves the movement of phosphorus through the lithosphere, hydrosphere, and biosphere. Unlike many other biogeochemical cycles, the atmosphere does not play a significant role in the movement of phosphorus, because phosphorus and phosphorus-based materials do not enter the gaseous phase readily, as the main source of gaseous phosphorus, phosphine, is only produced in isolated and specific conditions. Therefore, the phosphorus cycle is primarily examined studying the movement of orthophosphate (PO4)3-, the form of phosphorus that is most commonly seen in the environment, through terrestrial and aquatic ecosystems.
Uranium ore deposits are economically recoverable concentrations of uranium within Earth's crust. Uranium is one of the most common elements in 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.
Phosphate rich organic manure is a type of fertilizer used as an alternative to diammonium phosphate and single super phosphate.
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 Park City Formation is a fossiliferous sedimentary formation from the late Permian of Utah, Idaho, Wyoming, and Montana. It is defined by its cherty, gray to pinkish limestone, calcareous siltstone, and cherty sandstone. The rocks in this formation formed along a shallow marine continental shelf and were regularly interrupted by the Phosphoria Formation due to tectonic forces and sea level change.
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.
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.
Namibia is one of the first countries that issued mining licences regarding deep sea mining. studies that took place in 1970s discovered considerable amounts of phosphate deposits. The significance of seabed mining in Namibia's blue economy is highlighted by the country's status as a "phosphate factory". This is due to the exceptional upwellings of the Benguela Current ecosystem, a transboundary ocean current that spans from South Africa in the south to Angola in the north, passing through Namibia. Those deposits were found in depths between 180 and 300 meters below the sea level. In 2011 the Namibian government issued licences regarding the exploitation of the seabed phosphate resources after the necessary Environmental Impact Assessments (EIAs). The action plan that stood out was that of Namibian Marine Phosphates (NMP), a joint venture formed in 2008 between two Australian-based companies, Minemakers and Union Resources and Namibian-based Tungeni Investments. The so-called Sandpiper phosphate mining project outlay was introduced in January 2012 along with environmental reports regarding the effect this operation would have on marine life as well as the fishing industry and water quality changes. Those phosphorite resources are being found in continental shelves and slopes in America, Northern Spain, Morocco, Namibia, and South Africa which show a high potential for exploration.