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57-463: The Tukwila Formation is mainly composed of andesitic to dacitic volcanic sandstone , siltstone , shale , tuff - breccia , tuff, lahar , and carbonaceous shales. The tuff-breccia has an approximate age of 42 Ma . Vertebrate fauna mainly consists of just shark remains. Mainly one unnamed species of Goblin shark and one unnamed species belonging to the same genus as the Whitetip reef shark. Are

114-609: A face-centered cubic lattice and iron cations occupying interstitial sites . Half of the Fe cations occupy tetrahedral sites while the other half, along with Fe cations, occupy octahedral sites. The unit cell consists of thirty-two   O ions and unit cell length is a = 0.839 nm. As a member of the inverse spinel group, magnetite can form solid solutions with similarly structured minerals, including ulvospinel ( Fe 2 TiO 4 ) and magnesioferrite ( MgFe 2 O 4 ). Titanomagnetite, also known as titaniferous magnetite,

171-459: A basaltic magma must crystallize specific minerals that are then removed from the melt. This removal can take place in a variety of ways, but most commonly this occurs by crystal settling. The first minerals to crystallize and be removed from a basaltic parent are olivines and amphiboles . These mafic minerals settle out of the magma, forming mafic cumulates. There is geophysical evidence from several arcs that large layers of mafic cumulates lie at

228-566: A compass in Tasmania to keep navigation problems to the minimum. Magnetite crystals with a cubic habit are rare but have been found at Balmat, St. Lawrence County, New York , and at Långban, Sweden . This habit may be a result of crystallization in the presence of cations such as zinc. Magnetite can also be found in fossils due to biomineralization and are referred to as magnetofossils . There are also instances of magnetite with origins in space coming from meteorites . Biomagnetism

285-458: A component of protein plaques in the brain. Such plaques have been linked to Alzheimer's disease . Increased iron levels, specifically magnetic iron, have been found in portions of the brain in Alzheimer's patients. Monitoring changes in iron concentrations may make it possible to detect the loss of neurons and the development of neurodegenerative diseases prior to the onset of symptoms due to

342-680: A content of 57% to 63% silica and not more than about 6% alkali metal oxides. This places the andesite in the O2 field of the TAS classification . Basaltic andesite , with a content of 52% to 57% silica, is represented by the O1 field of the TAS classification but is not a distinct rock type in the QAPF classification. Andesite is usually light to dark grey in colour, due to its content of hornblende or pyroxene minerals. but can exhibit

399-528: A crystal structure phase transition from a monoclinic structure to a cubic structure known as the Verwey transition . Optical studies show that this metal to insulator transition is sharp and occurs around 120   K. The Verwey transition is dependent on grain size, domain state, pressure, and the iron-oxygen stoichiometry . An isotropic point also occurs near the Verwey transition around 130   K, at which point

456-430: A highly porous high-surface-area material, which enhances its effectiveness as a catalyst. Magnetite micro- and nanoparticles are used in a variety of applications, from biomedical to environmental. One use is in water purification: in high gradient magnetic separation, magnetite nanoparticles introduced into contaminated water will bind to the suspended particles (solids, bacteria, or plankton, for example) and settle to

513-431: A human health hazard, airborne magnetite is a result of pollution (specifically combustion). These nanoparticles can travel to the brain via the olfactory nerve, increasing the concentration of magnetite in the brain. In some brain samples, the nanoparticle pollution outnumbers the natural particles by as much as 100:1, and such pollution-borne magnetite particles may be linked to abnormal neural deterioration. In one study,

570-654: A new mechanism to generate andesite crust. Along with basalts, andesites are a component of the Martian crust . The presence of distinctive steep-sided domes on Venus suggests that andesite may have been erupted from large magma chambers where crystal settling could take place. Volcanic rocks : Subvolcanic rocks : Plutonic rocks : Picrite basalt Peridotite Basalt Diabase (Dolerite) Gabbro Andesite Microdiorite Diorite Dacite Microgranodiorite Granodiorite Rhyolite Microgranite Granite Magnetite Magnetite

627-499: A science important in understanding plate tectonics and as historic data for magnetohydrodynamics and other scientific fields . The relationships between magnetite and other iron oxide minerals such as ilmenite , hematite, and ulvospinel have been much studied; the reactions between these minerals and oxygen influence how and when magnetite preserves a record of the Earth's magnetic field . At low temperatures, magnetite undergoes

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684-518: A subducting slab generates magma resembling high-magnesium andesites. Notable stonemasonry structures built with andesite include: In 2009, researchers revealed that andesite was found in two meteorites (numbered GRA 06128 and GRA 06129) that were discovered in the Graves Nunataks icefield during the US Antarctic Search for Meteorites 2006/2007 field season. This possibly points to

741-525: A vast deposit of magnetite-bearing sand dunes in Peru . The dune field covers 250 square kilometers (100 sq mi), with the highest dune at over 2,000 meters (6,560 ft) above the desert floor. The sand contains 10% magnetite. In large enough quantities magnetite can affect compass navigation . In Tasmania there are many areas with highly magnetized rocks that can greatly influence compasses. Extra steps and repeated observations are required when using

798-649: A wide range of shading. Darker andesite can be challenging to distinguish from basalt, but a common rule of thumb , used away from the laboratory, is that andesite has a color index less than 35. The plagioclase in andesite varies widely in sodium content, from anorthite to oligoclase , but is typically andesine , in which anorthite makes up about 40 mol% of the plagioclase. The pyroxene minerals that may be present include augite , pigeonite , or orthopyroxene . Magnetite , zircon , apatite , ilmenite , biotite , and garnet are common accessory minerals. Alkali feldspar may be present in minor amounts. Andesite

855-416: Is Fe (Fe ) 2 (O ) 4 . This indicates that magnetite contains both ferrous ( divalent ) and ferric ( trivalent ) iron, suggesting crystallization in an environment containing intermediate levels of oxygen. The main details of its structure were established in 1915. It was one of the first crystal structures to be obtained using X-ray diffraction . The structure is inverse spinel , with O ions forming

912-496: Is a mineral and one of the main iron ores , with the chemical formula Fe Fe 3+ 2 O 4 . It is one of the oxides of iron , and is ferrimagnetic ; it is attracted to a magnet and can be magnetized to become a permanent magnet itself. With the exception of extremely rare native iron deposits, it is the most magnetic of all the naturally occurring minerals on Earth. Naturally magnetized pieces of magnetite, called lodestone , will attract small pieces of iron, which

969-517: Is a solid solution between magnetite and ulvospinel that crystallizes in many mafic igneous rocks. Titanomagnetite may undergo oxy-exsolution during cooling, resulting in ingrowths of magnetite and ilmenite. Natural and synthetic magnetite occurs most commonly as octahedral crystals bounded by {111} planes and as rhombic-dodecahedra . Twinning occurs on the {111} plane. Hydrothermal synthesis usually produces single octahedral crystals which can be as large as 10 mm (0.39 in) across. In

1026-703: Is also a chemical basis for cellular sensitivity to electric and magnetic fields ( galvanotaxis ). Pure magnetite particles are biomineralized in magnetosomes , which are produced by several species of magnetotactic bacteria . Magnetosomes consist of long chains of oriented magnetite particle that are used by bacteria for navigation. After the death of these bacteria, the magnetite particles in magnetosomes may be preserved in sediments as magnetofossils. Some types of anaerobic bacteria that are not magnetotactic can also create magnetite in oxygen free sediments by reducing amorphic ferric oxide to magnetite. Several species of birds are known to incorporate magnetite crystals in

1083-426: Is burnt (oxidized) to give magnetite or wüstite of a defined particle size. The magnetite (or wüstite) particles are then partially reduced, removing some of the oxygen in the process. The resulting catalyst particles consist of a core of magnetite, encased in a shell of wüstite, which in turn is surrounded by an outer shell of iron metal. The catalyst maintains most of its bulk volume during the reduction, resulting in

1140-409: Is composed predominantly of sodium-rich plagioclase plus pyroxene or hornblende . Andesite is the extrusive equivalent of plutonic diorite . Characteristic of subduction zones, andesite represents the dominant rock type in island arcs . The average composition of the continental crust is andesitic. Along with basalts, andesites are a component of the Martian crust . The name andesite

1197-447: Is derived from the Andes mountain range, where this rock type is found in abundance. It was first applied by Christian Leopold von Buch in 1826. Andesite is an aphanitic (fine-grained) to porphyritic (coarse-grained) igneous rock that is intermediate in its content of silica and low in alkali metals . It has less than 20% quartz and 10% feldspathoid by volume, with at least 65% of

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1254-726: Is how ancient peoples first discovered the property of magnetism. Magnetite is black or brownish-black with a metallic luster, has a Mohs hardness of 5–6 and leaves a black streak . Small grains of magnetite are very common in igneous and metamorphic rocks . The chemical IUPAC name is iron(II,III) oxide and the common chemical name is ferrous-ferric oxide . In addition to igneous rocks, magnetite also occurs in sedimentary rocks , including banded iron formations and in lake and marine sediments as both detrital grains and as magnetofossils . Magnetite nanoparticles are also thought to form in soils, where they probably oxidize rapidly to maghemite . The chemical composition of magnetite

1311-514: Is so characteristic of the Earth's unique plate tectonics that the Earth has been described as an "andesite planet". During subduction, the subducted oceanic crust is subjected to increasing pressure and temperature, leading to metamorphism . Hydrous minerals such as amphibole , zeolites , or chlorite (which are present in the oceanic lithosphere ) dehydrate as they change to more stable, anhydrous forms, releasing water and soluble elements into

1368-595: Is sometimes found in large quantities in beach sand. Such black sands (mineral sands or iron sands ) are found in various places, such as Lung Kwu Tan in Hong Kong; California , United States; and the west coast of the North Island of New Zealand. The magnetite, eroded from rocks, is carried to the beach by rivers and concentrated by wave action and currents. Huge deposits have been found in banded iron formations. These sedimentary rocks have been used to infer changes in

1425-453: Is still not well understood, and there has been a general lag in applying more modern, interdisciplinary techniques to the study of biomagnetism. Electron microscope scans of human brain-tissue samples are able to differentiate between magnetite produced by the body's own cells and magnetite absorbed from airborne pollution, the natural forms being jagged and crystalline, while magnetite pollution occurs as rounded nanoparticles . Potentially

1482-472: Is usually porphyritic , containing larger crystals ( phenocrysts ) of plagioclase formed prior to the extrusion that brought the magma to the surface, embedded in a finer-grained matrix . Phenocrysts of pyroxene or hornblende are also common. These minerals have the highest melting temperatures of the typical minerals that can crystallize from the melt and are therefore the first to form solid crystals. Classification of andesites may be refined according to

1539-452: Is usually related to the presence of biogenic crystals of magnetite, which occur widely in organisms. These organisms range from magnetotactic bacteria (e.g., Magnetospirillum magnetotacticum ) to animals, including humans, where magnetite crystals (and other magnetically sensitive compounds) are found in different organs, depending on the species. Biomagnetites account for the effects of weak magnetic fields on biological systems. There

1596-453: The Andes , magma often pools in the shallow crust creating magma chambers. Magmas in these reservoirs become evolved in composition (dacitic to rhyolitic) through both the process of fractional crystallization and partial melting of the surrounding country rock . Over time as crystallization continues and the system loses heat, these reservoirs cool. In order to remain active, magma chambers must have continued recharge of hot basaltic melt into

1653-448: The feldspar in the rock consisting of plagioclase . This places andesite in the basalt /andesite field of the QAPF diagram . Andesite is further distinguished from basalt by its silica content of over 52%. However, it is often not possible to determine the mineral composition of volcanic rocks, due to their very fine grain size, and andesite is then defined chemically as volcanic rock with

1710-442: The shield volcanoes characteristic of basalt, with its much lower viscosity resulting from its lower silica content and higher eruption temperature. Block lava flows are typical of andesitic lavas from composite volcanoes. They behave in a similar manner to ʻaʻā flows but their more viscous nature causes the surface to be covered in smooth-sided angular fragments (blocks) of solidified lava instead of clinkers. As with ʻaʻā flows,

1767-521: The QFM buffer. At still lower oxygen levels, magnetite forms a buffer with wüstite known as the MW buffer. The QFM and MW buffers have been used extensively in laboratory experiments on rock chemistry. The QFM buffer, in particular, produces an oxygen fugacity close to that of most igneous rocks. Commonly, igneous rocks contain solid solutions of both titanomagnetite and hemoilmenite or titanohematite. Compositions of

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1824-408: The base of the crust. Once these mafic minerals have been removed, the melt no longer has a basaltic composition. The silica content of the residual melt is enriched relative to the starting composition. The iron and magnesium contents are depleted. As this process continues, the melt becomes more and more evolved eventually becoming andesitic. Without continued addition of mafic material, however,

1881-460: The bottom of the fluid, allowing the contaminants to be removed and the magnetite particles to be recycled and reused. This method works with radioactive and carcinogenic particles as well, making it an important cleanup tool in the case of heavy metals introduced into water systems. Another application of magnetic nanoparticles is in the creation of ferrofluids . These are used in several ways. Ferrofluids can be used for targeted drug delivery in

1938-410: The brain – magnetite, hemoglobin (blood) and ferritin (protein), and areas of the brain related to motor function generally contain more iron. Magnetite can be found in the hippocampus . The hippocampus is associated with information processing, specifically learning and memory. However, magnetite can have toxic effects due to its charge or magnetic nature and its involvement in oxidative stress or

1995-559: The characteristic nanoparticles were found in the brains of 37 people: 29 of these, aged 3 to 85, had lived and died in Mexico City, a significant air pollution hotspot. Some of the further eight, aged 62 to 92, from Manchester, England, had died with varying severities of neurodegenerative diseases. Such particles could conceivably contribute to diseases like Alzheimer's disease . Though a causal link has not yet been established, laboratory studies suggest that iron oxides such as magnetite are

2052-505: The following: This article about a specific stratigraphic formation in the United States is a stub . You can help Misplaced Pages by expanding it . Andesitic Andesite ( / ˈ æ n d ə z aɪ t / ) is a volcanic rock of intermediate composition . In a general sense, it is the intermediate type between silica -poor basalt and silica-rich rhyolite . It is fine-grained ( aphanitic ) to porphyritic in texture, and

2109-402: The human body. The magnetization of the particles bound with drug molecules allows "magnetic dragging" of the solution to the desired area of the body. This would allow the treatment of only a small area of the body, rather than the body as a whole, and could be highly useful in cancer treatment, among other things. Ferrofluids are also used in magnetic resonance imaging (MRI) technology. For

2166-448: The magnetic fields the organism was exposed to, potentially allowing scientists to learn about the migration of the organism or about changes in the Earth's magnetic field over time. Living organisms can produce magnetite. In humans, magnetite can be found in various parts of the brain including the frontal , parietal , occipital , and temporal lobes , brainstem , cerebellum and basal ganglia . Iron can be found in three forms in

2223-454: The magnetite with needle-shaped particles of gamma ferric oxide (γ-Fe 2 O 3 ). Approximately 2–3% of the world's energy budget is allocated to the Haber Process for nitrogen fixation, which relies on magnetite-derived catalysts. The industrial catalyst is obtained from finely ground iron powder, which is usually obtained by reduction of high-purity magnetite. The pulverized iron metal

2280-437: The melt will eventually reach a rhyolitic composition. This produces the characteristic basalt-andesite-rhyolite association of island arcs, with andesite the most distinctive rock type. Partially molten basalt in the mantle wedge moves upwards until it reaches the base of the overriding crust. Once there, the basaltic melt can either underplate the crust, creating a layer of molten material at its base, or it can move into

2337-418: The mineral pairs are used to calculate oxygen fugacity: a range of oxidizing conditions are found in magmas and the oxidation state helps to determine how the magmas might evolve by fractional crystallization . Magnetite also is produced from peridotites and dunites by serpentinization . Lodestones were used as an early form of magnetic compass . Magnetite has been a critical tool in paleomagnetism ,

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2394-582: The mineral. In the municipalities of Molinaseca, Albares, and Rabanal del Camino, in the province of León (Spain), there is a magnetite deposit in Ordovician terrain, considered one of the largest in Europe. It was exploited between 1955 and 1982. Deposits are also found in Norway , Romania , and Ukraine . Magnetite-rich sand dunes are found in southern Peru. In 2005, an exploration company, Cardero Resources, discovered

2451-512: The molten interior of the flow, which is kept insulated by the solidified blocky surface, advances over the rubble that falls off the flow front. They also move much more slowly downhill and are thicker in depth than ʻaʻā flows. Though andesite is common in other tectonic settings, it is particularly characteristic of convergent plate margins . Even before the Plate Tectonics Revolution , geologists had defined an andesite line in

2508-492: The most abundant phenocryst . For example, if hornblende is the principal phenocryst mineral, the andesite will be described as a hornblende andesite . Andesite lava typically has a viscosity of 3.5 × 10 cP (3.5 × 10 Pa⋅s) at 1,200 °C (2,190 °F). This is slightly greater than the viscosity of smooth peanut butter . As a result, andesitic volcanism is often explosive, forming tuffs and agglomerates . Andesite vents tend to build up composite volcanoes rather than

2565-510: The overlying wedge of mantle. Fluxing water into the wedge lowers the solidus of the mantle material and causes partial melting. Due to the lower density of the partially molten material, it rises through the wedge until it reaches the lower boundary of the overriding plate. Melts generated in the mantle wedge are of basaltic composition, but they have a distinctive enrichment of soluble elements (e.g. potassium (K), barium (Ba), and lead (Pb)) which are contributed from sediment that lies at

2622-441: The overriding plate in the form of dykes . If it underplates the crust, the basalt can (in theory) cause partial melting of the lower crust due to the transfer of heat and volatiles. Models of heat transfer, however, show that arc basalts emplaced at temperatures 1100–1240 °C cannot provide enough heat to melt lower crustal amphibolite . Basalt can, however, melt pelitic upper crustal material. In continental arcs, such as

2679-614: The oxygen content of the atmosphere of the Earth. Large deposits of magnetite are also found in the Atacama region of Chile ( Chilean Iron Belt ); the Valentines region of Uruguay; Kiruna , Sweden; the Tallawang region of New South Wales; and in the Adirondack Mountains of New York in the United States. Kediet ej Jill , the highest mountain of Mauritania , is made entirely of

2736-403: The presence of mineralizers such as 0.1   M HI or 2   M NH 4 Cl and at 0.207   MPa at 416–800 °C, magnetite grew as crystals whose shapes were a combination of rhombic-dodechahedra forms. The crystals were more rounded than usual. The appearance of higher forms was considered as a result from a decrease in the surface energies caused by the lower surface to volume ratio in

2793-405: The production of free radicals . Research suggests that beta-amyloid plaques and tau proteins associated with neurodegenerative disease frequently occur after oxidative stress and the build-up of iron. Some researchers also suggest that humans possess a magnetic sense, proposing that this could allow certain people to use magnetoreception for navigation. The role of magnetite in the brain

2850-534: The relationship between magnetite and ferritin . In tissue, magnetite and ferritin can produce small magnetic fields which will interact with magnetic resonance imaging (MRI) creating contrast. Huntington patients have not shown increased magnetite levels; however, high levels have been found in study mice. Due to its high iron content, magnetite has long been a major iron ore . It is reduced in blast furnaces to pig iron or sponge iron for conversion to steel . Audio recording using magnetic acetate tape

2907-427: The rounded crystals. Magnetite has been important in understanding the conditions under which rocks form. Magnetite reacts with oxygen to produce hematite , and the mineral pair forms a buffer that can control how oxidizing its environment is (the oxygen fugacity ). This buffer is known as the hematite-magnetite or HM buffer. At lower oxygen levels, magnetite can form a buffer with quartz and fayalite known as

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2964-420: The sign of the magnetocrystalline anisotropy constant changes from positive to negative. The Curie temperature of magnetite is 580 °C (853 K; 1,076 °F). If magnetite is in a large enough quantity it can be found in aeromagnetic surveys using a magnetometer which measures magnetic intensities. Solid magnetite particles melt at about 1,583–1,597 °C (2,881–2,907 °F). Magnetite

3021-541: The system. When this basaltic material mixes with the evolved rhyolitic magma, the composition is returned to andesite, its intermediate phase. Evidence of magma mixing is provided by the presence of phenocrysts in some andesites that are not in chemical equilibrium with the melt in which they are found. High-magnesium andesites ( boninites ) in island arcs may be primitive andesites, generated from metasomatized mantle. Experimental evidence shows that depleted mantle rock exposed to alkali fluids such as might be given off by

3078-585: The top of the subducting plate. Although there is evidence to suggest that the subducting oceanic crust may also melt during this process, the relative contribution of the three components (crust, sediment, and wedge) to the generated basalts is still a matter of debate. Basalt thus formed can contribute to the formation of andesite through fractional crystallization, partial melting of crust, or magma mixing, all of which are discussed next. Intermediate volcanic rocks are created via several processes: To achieve andesitic composition via fractional crystallization ,

3135-453: The upper beak for magnetoreception , which (in conjunction with cryptochromes in the retina ) gives them the ability to sense the direction, polarity , and magnitude of the ambient magnetic field . Chitons , a type of mollusk, have a tongue-like structure known as a radula , covered with magnetite-coated teeth, or denticles . The hardness of the magnetite helps in breaking down food. Biological magnetite may store information about

3192-481: The western Pacific that separated basalt of the central Pacific from andesite further west. This coincides with the subduction zones at the western boundary of the Pacific Plate . Magmatism in island arc regions comes from the interplay of the subducting plate and the mantle wedge , the wedge-shaped region between the subducting and overriding plates. The presence of convergent margins dominated by andesite

3249-476: Was developed in the 1930s. The German magnetophon first utilized magnetite powder that BASF coated onto cellulose acetate before soon switching to gamma ferric oxide for its superior morphology. Following World War II , 3M Company continued work on the German design. In 1946, the 3M researchers found they could also improve their own magnetite-based paper tape, which utilized powders of cubic crystals, by replacing

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