Evaporiters

Evaporiters is a rarely used term that refers to evaporites, a class of chemical sedimentary rocks formed by the precipitation of minerals from evaporating saline waters. In modern geology, evaporites is the preferred term, and evaporiters is largely considered obsolete or regional usage.

Formation and composition: Evaporites develop in settings where bodies of seawater or saline lakes become isolated and undergo high rates of evaporation. As concentration of dissolved ions increases, minerals precipitate in a characteristic sequence depending on chemistry and salinity. Common minerals include halite (sodium chloride), gypsum (calcium sulfate dihydrate), anhydrite (calcium sulfate), and, in potassium-rich environments, sylvite (potassium chloride) and carnallite (potassium magnesium chloride). Borates and other salts may also occur. Deposits typically form as thick, layered beds that record repeated cycles of evaporation and recharge.

Environments and distribution: Classic evaporite basins occur in arid to semi-arid regions with restricted basins, such as coastal sabkhas, salinas, and playa lakes. Ancient evaporites are widespread in many continents and provide important records of past climate and sea level. Large modern and ancient deposits are associated with restricted marine basins, arid deserts, and evaporating continental lakes.

Economic significance: Evaporite minerals are economically important. Rock salt supplies large quantities of sodium chloride for chemical and deicing uses; potash minerals provide key fertilizers; gypsum and anhydrite are essential in cement and plaster industries. Evaporite sequences also influence reservoir quality in petroleum geology and can host significant brine resources.

See also: Evaporite, Halite, Gypsum, Potash.