To use all functions of this page, please activate cookies in your browser.
With an accout for my.chemeurope.com you can always see everything at a glance – and you can configure your own website and individual newsletter.
- My watch list
- My saved searches
- My saved topics
- My newsletter
Additional recommended knowledge
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. 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;
Evaporite formations need not be composed entirely of halite salt. 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.
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.
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.
Halite formations are famous for their ability to form diapirs which produce ideal locations for trapping petroleum deposits.
Major groups of evaporite minerals
The minerals precipitate out of solution in the reverse order of their solubilities, such that the order of precipitation from sea water is
The abundance of rocks formed by seawater precipitation is in the same order as the precipitation given above. 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.
Evaporites can also be easily recrystallized in laboratories in order to postulate the specific characteristics of their formation.
|This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Evaporite". A list of authors is available in Wikipedia.|