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A sample of evaporite material
A sample of evaporite material

Evaporites (pronounced /iˈvæpəraɪt/) are water-soluble, mineral sediments that result from the evaporation of bodies of surficial water. A mineral is a naturally occurring substance formed through geological processes that has a characteristic chemical composition a highly ordered atomic structure and specific Sedimentary rock is one of the three main rock types (the others being igneous and Metamorphic rock) Evaporation is the process by which Molecules in a Liquid state (e Water is a common Chemical substance that is essential for the survival of all known forms of Life. Evaporites are considered sedimentary rocks.

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Formation of evaporite rocks

Although all water bodies on the surface and in aquifers contain dissolved salts, the water must evaporate into the atmosphere for the minerals to precipitate. For this to happen the water body must enter a restricted environment where water input into this environment remains below the net rate of evaporation. This is usually an arid environment with a small basin fed by a limited input of water. In general terms the Climate of a local or region is said to be arid when it is characterized by a severe lack of available Water, to the extent of hindering When evaporation occurs, the remaining water is enriched in salts, and they precipitate when the water becomes oversaturated.

Evaporite depositional environments

Evaporite depositional environments which meet the above conditions include;

Evaporitic formations

Evaporite formations need not be composed entirely of halite salt. A graben is a depressed block of land bordered by parallel faults Graben is German for ditch. In Geology, a rift is a place where the Earth 's crust and Lithosphere are being pulled apart and is an example of Extensional tectonics The Afar Depression (also called the Danakil Depression or the Afar Triangle) is a Geological depression in the Horn of Africa, where it NOTE This intro is the result of careful NPOV work Please do not make potentially controversial edits to it without first discussing on the talk page Death Valley is the lowest driest and hottest Valley in the United States. California ( is a US state on the West Coast of the United States, along the Pacific Ocean. The Dead Sea (יָם הַ‏‏מֶ‏ּ‏לַ‏ח, "Sea of Salt"البَحْر المَيّت, "Dead Sea" is a salt lake between Jordan, officially the Hashemite Kingdom of Jordan (الأردنّ al-Urdunn) is an Arab country in Southwest Asia spanning the southern The Simpson Desert occupies approximately 176500 square kilometres of central Australia. Western Australia is a state occupying the entire western third of the Australian continent. Great Salt Lake, located in the northern part of the US state of Utah, is the largest salt lake in the western hemisphere the fourth-largest terminal The State of Utah (ˈjuːtɔː or) is a western state of the United States. The Great Artesian Basin provides the only reliable source of Water through much of inland Australia. For a topic outline on this subject see List of basic Australia topics. Sabkha is a transliteration of the Arabic word for a Salt flat. The Sahara (الصحراء الكبرى aṣ-ṣaḥrā´ al-kubra, "The Great Desert" is the world's largest hot Desert and the world's second largest The Namib Desert is a Desert in Namibia and southwest Angola which forms part of the Namib-Naukluft National Park. In fact, most evaporite formations do not contain more than a few percent of evaporite minerals, the remainder being composed of the more typical detrital clastic rocks and carbonates.

For a formation to be recognised as evaporitic it may simply require recognition of halite pseudomorphs, sequences composed of some proportion of evaporite minerals, and recognition of mud crack textures or other textures. In Geology, a pseudomorph is a Mineral compound resulting from a substitution process in which the appearance and dimensions remain constant but the mineral which Rock microstructure includes the texture of a rock and the small scale rock structures

Economic importance of evaporites

Evaporites are important economically because of their mineralogy, their physical properties in-situ and their behaviour within the subsurface.

Evaporite minerals, especially nitrate minerals, are economically important in Peru and Chile. Nitrate minerals are often mined for use in the production on fertilizer and explosives. Fertilizers ( also spelt fertiliser are chemical compounds given to Plants to promote growth they are usually applied either through the soil for uptake by plant An explosive material is a material that either is chemically or otherwise Energetically unstable or produces a sudden expansion of the material usually accompanied

Thick halite deposits are expected to become an important location for the disposal of nuclear waste because of their geologic stability, predictable engineering and physical behaviour and imperviousness to groundwater. Radioactive wastes are Waste types containing radioactive Chemical elements that do not have a practical purpose

Halite formations are famous for their ability to form diapirs which produce ideal locations for trapping petroleum deposits. A diapir (ˈdaɪəpɪər) ( French, from Greek diapeirein, to pierce through is an Intrusion caused by Buoyancy and Pressure Petroleum ( L petroleum, from Greek πετρέλαιον, lit

Major groups of evaporite minerals

Evaporite minerals start to precipitate when their concentration in water reaches such a level that they can no longer exist as solutes. Precipitation is the formation of a Solid in a Solution during a Chemical reaction. In Chemistry, a solution is a Homogeneous Mixture composed of two or more substances

The minerals precipitate out of solution in the reverse order of their solubilities, such that the order of precipitation from sea water is

  1. Calcite (CaCO3) and dolomite (CaMg(CO3)2)
  2. Gypsum (CaSO4-2H2O) and anhydrite (CaSO4). Calcite is a carbonate mineral and the most stable polymorph of Calcium carbonate ( Ca[[carbon C]] O 3 Dolomite (ˈdɒləmaɪt is the name of a Sedimentary Carbonate rock and a Mineral, both composed
  3. Halite (i. e. common salt, NaCl)
  4. Potassium and magnesium salts

The abundance of rocks formed by seawater precipitation is in the same order as the precipitation given above. Potassium (pəˈtæsiəm is a Chemical element. It has the symbol K (kalium from qalīy Atomic number 19 and Atomic mass 39 Magnesium (mægˈniːziəm is a Chemical element with the symbol Mg, Atomic number 12 Atomic weight 24 Thus, limestone (calcite) and dolomite are more common than gypsum, which is more common than halite, which is more common than potassium and magnesium salts. Limestone is a Sedimentary rock composed largely of the Mineral Calcite ( Calcium carbonate: CaCO3 Calcite is a carbonate mineral and the most stable polymorph of Calcium carbonate ( Ca[[carbon C]] O 3 Dolomite (ˈdɒləmaɪt is the name of a Sedimentary Carbonate rock and a Mineral, both composed Gypsum is a very soft Mineral composed of Calcium sulfate dihydrate with the Chemical formula Ca[[sulfur S]] O 4·2 Halite is the Mineral form of Sodium chloride, Na[[chlorine Cl]] commonly known as rock salt. Potassium (pəˈtæsiəm is a Chemical element. It has the symbol K (kalium from qalīy Atomic number 19 and Atomic mass 39 Magnesium (mægˈniːziəm is a Chemical element with the symbol Mg, Atomic number 12 Atomic weight 24

Evaporites can also be easily recrystallized in laboratories in order to postulate the specific characteristics of their formation. Recrystallization (see also Crystallization) is a physical process that has meanings in Chemistry, Metallurgy and Geology.

See also

References

Dictionary

evaporite

-noun

  1. the salty, crusty, sediment that remains after sea water evaporates
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