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42-547: Vent geology, biology, and fluid content make Rainbow comparable to other hot hydrothermal vents of the Azores such as Lucky Strike and Menez Gwen. However; chlorinity , metal concentration, and pH distinguish it from neighboring vent fields. As a hot, ultramafic-hosted vent field, pH levels of fluids are extremely low with much H 2 and CH 4 generated from water interactions with mafic igneous rocks . Though not actively considered for development, Rainbow lies within

84-501: A scarp . Chloride concentrations from vent fluids suggest a common heat source for the site, though the location and geometry of heat sources is unknown. Due to the extensive faulting at the Rainbow massif, cold ocean seawater is able to permeate deep into the seafloor. Water circulates down a fault line, actively reacting with various sediment and rock layers until it is warmed by an underlying heat source. When warmed, it can undergo

126-446: A solid solution is also a way to strengthen alloys . Precipitation of ceramic phases in metallic alloys such as zirconium hydrides in zircaloy cladding of nuclear fuel pins can also render metallic alloys brittle and lead to their mechanical failure. Correctly mastering the precise temperature and pressure conditions when cooling down spent nuclear fuels is therefore essential to avoid damaging their cladding and to preserve

168-425: A chemical reaction. When a barium chloride solution reacts with sulphuric acid , a white precipitate of barium sulphate is formed. When a potassium iodide solution reacts with a lead(II) nitrate solution, a yellow precipitate of lead(II) iodide is formed. Precipitate formation is useful in the detection of the type of cation in a salt . To do this, an alkali first reacts with the unknown salt to produce

210-430: A common heat source for the vents. There may, however, be many heat sources at Rainbow considering the complex faulting tectonics, and extensive amounts of gabbro and peridotite. Rainbow has been a long-lived environment for microbial life, with a great diversity of archaea and bacteria at the vent field. Microbes are known to utilize energy from H 2 gas and H 2 S oxidation, with some chemotrophs belonging to

252-423: A less soluble compound because of its lower chemical valence: The Walden reductor made of tiny silver crystals obtained by the immersion of a copper wire into a solution of silver nitrate is used to reduce to their lower valence any metallic ion located above the silver couple (Ag + 1 e → Ag) in the redox potential scale. Without sufficient attraction forces ( e.g. , Van der Waals force ) to aggregate

294-492: A liquid solution". The solid formed is called the precipitate . In case of an inorganic chemical reaction leading to precipitation, the chemical reagent causing the solid to form is called the precipitant . The clear liquid remaining above the precipitated or the centrifuged solid phase is also called the supernate or supernatant . The notion of precipitation can also be extended to other domains of chemistry ( organic chemistry and biochemistry ) and even be applied to

336-440: A number of organic carbon molecules, from alkanes and phenol to complicated polycyclic aromatic hydrocarbons (PAHS) and biogenic fatty acids . These organic carbon molecules suggest organisms living within the vents, harnessing chemosynthetic reactions to metabolize . Serpentinization reactions occur with hydrothermal circulation causing water to react with hot iron-containing minerals, releasing H 2 gas and transforming

378-633: A phase transition - often resulting in dramatic changes to fluid chemistry. Super-heated vent fluids then rise and are ejected from the seafloor, where a dramatic drop in temperature from cold-water mixing can cause some fluid chemicals to precipitate out and form chimneys. With relatively little basalt within a kilometer of the vent field, most reactions influencing the vent fluids during hydrothermal circulation come from differing degrees of serpentinization and veining of peridotites. Olivine -rich rocks such as troctolites undergo significant alteration, being partially replaced by serpentine and magnetite. There

420-434: A precipitate that is the hydroxide of the unknown salt. To identify the cation, the color of the precipitate and its solubility in excess are noted. Similar processes are often used in sequence – for example, a barium nitrate solution will react with sulfate ions to form a solid barium sulfate precipitate, indicating that it is likely that sulfate ions are present. A common example of precipitation from aqueous solution

462-413: A ridge system. Depending on the chemical stability of the elements, water entering the seafloor will therefore exhibit different chemical characteristics when it comes back out. At Rainbow, phase separation is a suggested cause for particularly high concentrations of chloride, trace elements, and hydronium, as they differ greatly from similar MAR vents like Logatchev. Furthermore, Rainbow vent fluids have

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504-669: A slow-spreading ridge at approximately 2.2 cm/yr, extensive faulting has uplifted gabbro and peridotite and exposed ultramafic rock to cold seawater. Faulting may also be responsible for magnitude 3 - 3.5 earthquakes observed in hydroacoustic data, suggesting that the region is tectonically active. Unlike high-temperature basalt systems, this ultramafic setting is associated with a positive magnetic anomaly ; postulated to come from magnetite precipitation. The active Rainbow site exhibits numerous active and inactive chimneys at serpentinized peridotite outcrops, distinguishable from sediment cover either by protruding from sediment or at

546-472: A trophic habitat that is original and delicate. In these environments bacteria replace plants, through chemosynthesis, by transforming carbon molecules and nutrients into organic matter. Many of these ecosystems were only discovered in the Atlantic between 1977 and 1992. Precipitation (chemistry) In an aqueous solution , precipitation is the "sedimentation of a solid material (a precipitate) from

588-452: Is a very popular site for scientific expeditions involving intrusive long-term monitoring, environmental manipulation, and geological sampling. It is also the only vent field on the MAR which has been visited by tourists. Due to some veining processes, ore extraction and mining are another activity than may upset ecosystems of the massif. Rainbow has a tricky history regarding preservation, as

630-400: Is added to the dimethylformamide (DMF) solution in which the reaction occurred, and the product precipitates. Precipitation is useful in purifying many other products: e.g. , crude bmim -Cl is taken up in acetonitrile , and dropped into ethyl acetate , where it precipitates. Proteins purification and separation can be performed by precipitation in changing the nature of the solvent or

672-482: Is also considered in this group; located between São Miguel and Terceira , the seamount is one of the highest independent seamounts in the archipelago and home to a thriving marine volcanic habitat. In 2010, a shallow hydrothermal field was discovered off the Ponta da Espalamaca, on the island of Faial , showing evidence of de-gasification. Efforts are being made to classify these areas as protected marine areas under

714-459: Is evidence of high-temperature serpentinite alteration on some samples with pre-existing serpentinite, demonstrating overprinting of serpentinites with higher iron content. Mylonic peridotites at the vent field show plastic deformation then overprinted by serpentine and chlorite . Rainbow exhibits very acidic vent fluids (pH ~2.8) from hydronium ions released from numerous ultramafic rock interactions during vent circulation. Fluids also contain

756-419: Is in ethanol precipitation of DNA . In solid phases, precipitation occurs if the concentration of one solid is above the solubility limit in the host solid, due to e.g. rapid quenching or ion implantation , and the temperature is high enough that diffusion can lead to segregation into precipitates. Precipitation in solids is routinely used to synthesize nanoclusters . In metallurgy , precipitation from

798-532: Is listed by OSPAR as protected marine nature preserve with an MPA size of 22.15 km. Hydrothermal vents and seamounts of the Azores The hydrothermal vents and seamounts of the Azores ( Portuguese : fontes hidrotermais e montes submarinos dos Açores ) are a series of Atlantic seamounts and hydrothermal vents that are part of the Mid-Atlantic Ridge system, giving rise to

840-408: Is that of silver chloride . When silver nitrate (AgNO 3 ) is added to a solution of potassium chloride (KCl) the precipitation of a white solid (AgCl) is observed. The ionic equation allows to write this reaction by detailing the dissociated ions present in aqueous solution. The Walden reductor is an illustration of a reduction reaction directly accompanied by the precipitation of

882-522: The Asgard archaea tree. The Asgard archaea are a very recent discovery with a theorized ancestry in evolution between prokaryotes and eukaryotes . Some of the biogenic alkanes found within vent fluids are suggestive of sulfide-oxidizing bacteria or archaea. However, there is also abundant evidence of abiotic production of organic and inorganic molecules at Rainbow, such as methane and carbonate , which may have been supportive of early life. Due to

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924-490: The Menez Gwen field is a breeding ground for mussels, shrimp and crab species. These hydrothermal environments are characterized by an elevated number of endemic and exclusive species; such as shrimp (like Rimicaris exoculata ) or fish (such as Pachycara saldanhai ), among others that exist in these areas. In addition, the chemotrophic subaquatic environment (as opposed to phototropic lithosphere ) has resulted in

966-414: The Atlantic the formative processes continue to occur producing new land area such as the volcanic eruptions at Capelinhos or Serreta , but also through the venting of gases and pillow lavas, supporting a rich ecosystem. Hydrothermal vent is the name given to a type of fumarole found in the ocean, with elevated temperatures, rich in dissolved minerals, resulting from the infiltration of ocean water into

1008-862: The Convention for the Protection of the North Mid-Atlantic (OSPAR Convention) and in accordance with the requirements of the Habitats Directive. The World Wildlife Fund recognizes these efforts, awarding the Azorean regional government with the honorific "Gift to the Earth" prize for their contribution to the preservation of these marine ecosystems. The Azores also provide a good place to study deep-ocean hydrothermal vents; various investigative projects by many scientists have documented

1050-631: The Earth's crust and magma chambers. When expelled and contacting the cold waters, it results in a precipitation of mineral deposits, forming a characteristic plume of muddy waters and expelled minerals. Seven large hydrothermal fields have been discovered within the waters of the Azores: These sites, with the exception of the Moytirra system, are located in the southern part of the archipelago, and have been investigated by national and international scientists. The isolated Dom João de Castro Bank

1092-564: The Mid-Atlantic Ridge. The islands of the Azores are the visible representation of the complex ridge of undersea mountains that extend from Iceland to Antarctic. Below the waters of the Azores are undersea valleys and large mountains that are many times larger than the terrestrial continental mountain ranges. Formed by divergent boundary plate tectonics, the region is fractured and susceptible to earthquakes and natural volcanism, resulting in effusive or explosive volcanism. Beneath

1134-621: The MoMAR (Monitoring of the Mid Atlantic Ridge) survey area for a marine observatory. Rainbow has had a number of visits since its initial discovery in 1994. Remotely Operated Vehicles (ROVs), submersibles , and Conductivity Temperature Depth (CTD) probes have been deployed to sample, characterize, and explore the vent field. Rainbow is located on a massif at 2,275–2,335 m (7,464–7,661 ft) depth, shared with two fossil (mostly inactive) vent sites Ghost City and Clamstone. As

1176-424: The Rainbow massif, with Ghost City containing gastropod and clam remains that are aged at nearly 111,000 years old. Shell-rich carbonates have been found at Clamstone, which may be as old as 25,000 years. Rainbow, as with all other deepwater vent systems, is a location of highly specialized biology and sensitive geological structures. Due to its significance as an accessible and examplar ultramafic system, Rainbow

1218-637: The archipelago and bathymetric region of the Azores . These geological structures, formed from masses of basalt (typical of mid-ocean regions), are of a geomorphological interest due to their rich deposits of ore . In addition it fosters a rich ecosystem of diverse subaquatic plant and animal life. There are food chains within this environment, for example, that are purely chemosynthetic , and do not need sunlight for photosynthesis . The Azores consists of an extensive marine and terrestrial system of hundreds of active submarine mounts and volcanoes that extend from

1260-411: The base rock. Serpentinization may also be responsible for a significant amount of methane produced at Rainbow. Vent fluids are known to travel many kilometers northeast from their associated vents, depositing any unreacted elements to the seafloor far away from their source. Phase separation can occur when seawater is heated to a high enough temperature it will form a second phase. At pressure below

1302-450: The critical point (298 bar, 407 °C for seawater), the seawater boils and produces a vapor phase. At pressure above the critical pressure a saline brine forms as the second phase. In the subsurface, gravitational forces can lead the two phases to separate. Waters circulating deep within Rainbow rise to a high enough pressure or temperature so that they react with the rock and chemical constituents are dissolved into or precipitate out of

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1344-585: The highest concentrations of many elements found at the Azores vents, such as hydrogen , transition metals , and rare earth elements (REE). Due to the extreme endmember pH, chloride is hypothesized to act as a dominant cation and therefore forms many weak complexes with other elements at high temperatures. These complexes become unstable when pH rises or temperature decreases, therefore releasing many transition metals and REEs. Observed endmember fluid samples taken at different vent sites are of very similar manganese and magnesium concentrations, which suggests

1386-591: The hot temperatures, low pH, and longevity of the vent activity, there is a strong case for life to originate at sites similar to the Rainbow Massif. Regarding macrofauna , the Rainbow Massif has been supportive of many kinds of decapods and mollusks , such as Alvinocarididae and Bathymodiolus respectively, feeding where nutrient-rich vent fluids interact with the cold bathypelagic waters. Rainbow exhibits fossils of many kinds of vesicomyid and thyasirid shells. Fossils have been dated at other sites on

1428-401: The photograph here beside: [REDACTED] Precipitation may also occur when an antisolvent (a solvent in which the product is insoluble) is added, drastically reducing the solubility of the desired product. Thereafter, the precipitate may be easily separated by decanting , filtration , or by centrifugation . An example would be the synthesis of Cr tetraphenylporphyrin chloride: water

1470-406: The product of the reaction is insoluble in the solvent used for the reaction. Thus, it precipitates as it is formed, preferably forming pure crystals . An example of this would be the synthesis of porphyrins in refluxing propionic acid . By cooling the reaction mixture to room temperature, crystals of the porphyrin precipitate, and are collected by filtration on a Büchner filter as illustrated by

1512-621: The relationship between divergent boundary zones and subaquatic ecosystems. Communities of living creatures were discovered in the Lucky Strike Hydrothermal Field and the Menez Gwen Hydrothermal Field , both located within the Azores' Exclusive Economic Zone . The Lucky Strike field has a bio-geographically fauna, distinct from that of other hydrothermal fields in the archipelago, characterized by mussels and associated species. Meanwhile,

1554-498: The site is within the OSPAR Maritime Area and just outside of Portugal's exclusive economic zone similarly to another vent field, Saldanha. Portugal was unable to distinguish Rainbow as residing off of the extended Azores shelf region - therefore rendering it unqualified for OSPAR protection as a High Seas location. The World Wide Fund for Nature (WWF) lobbied for Rainbow's protection in 2005 and as of 2006, Rainbow

1596-400: The solid particles together and to remove them from solution by gravity ( settling ), they remain in suspension and form colloids . Sedimentation can be accelerated by high speed centrifugation . The compact mass thus obtained is sometimes referred to as a 'pellet'. Digestion, or precipitate ageing , happens when a freshly formed precipitate is left, usually at a higher temperature , in

1638-405: The solid phases (e.g. metallurgy and alloys ) when solid impurities segregate from a solid phase. The precipitation of a compound may occur when its concentration exceeds its solubility . This can be due to temperature changes, solvent evaporation, or by mixing solvents. Precipitation occurs more rapidly from a strongly supersaturated solution. The formation of a precipitate can be caused by

1680-484: The solution from which it precipitates. It results in purer and larger recrystallized particles. The physico-chemical process underlying digestion is called Ostwald ripening . While precipitation reactions can be used for making pigments , removing ions from solution in water treatment , and in classical qualitative inorganic analysis , precipitation is also commonly used to isolate the products of an organic reaction during workup and purification operations. Ideally,

1722-430: The value of its relative permittivity ( e.g. , by replacing water by ethanol ), or by increasing the ionic strength of the solution. As proteins have complex tertiary and quaternary structures due to their specific folding and various weak intermolecular interactions ( e.g. , hydrogen bridges), these superstructures can be modified and proteins denaturated and precipitated. Another important application of an antisolvent

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1764-408: The vent fluid. Chemical concentrations in the fluid are further modified when it undergoes phase separation because volatile constituents are concentrated in the vapor rich phase and metal ions in the brine. Phase separation carries great significance for chlorine , an abundant element in seawater with few reactions outside of phase separation, and is often normalized to assess thermodynamics within

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