Dolomitization is a geological process by which the

carbonate A carbonate is a salt of carbonic acid (H2CO3), characterized by the presence of the carbonate ion, a polyatomic ion with the formula . The word ''carbonate'' may also refer to a carbonate ester, an organic compound containing the carbonate g ...

mineral In geology and mineralogy, a mineral or mineral species is, broadly speaking, a solid chemical compound with a fairly well-defined chemical composition and a specific crystal structure that occurs naturally in pure form.John P. Rafferty, ed. ...

dolomite is formed when

magnesium Magnesium is a chemical element with the symbol Mg and atomic number 12. It is a shiny gray metal having a low density, low melting point and high chemical reactivity. Like the other alkaline earth metals (group 2 of the periodic ta ...

ion An ion () is an atom or molecule with a net electrical charge. The charge of an electron is considered to be negative by convention and this charge is equal and opposite to the charge of a proton, which is considered to be positive by conv ...

s replace

calcium Calcium is a chemical element with the symbol Ca and atomic number 20. As an alkaline earth metal, calcium is a reactive metal that forms a dark oxide-nitride layer when exposed to air. Its physical and chemical properties are most similar ...

ions in another carbonate mineral,

calcite Calcite is a carbonate mineral and the most stable polymorph of calcium carbonate (CaCO3). It is a very common mineral, particularly as a component of limestone. Calcite defines hardness 3 on the Mohs scale of mineral hardness, based on scrat ...

. It is common for this mineral alteration into dolomite to take place due to evaporation of water in the

sabkha A sabkha ( ar, سبخة) is a coastal, supratidal mudflat or sandflat in which evaporite-saline minerals accumulate as the result of semiarid to arid climate. Sabkhas are gradational between land and intertidal zone within restricted coastal p ...

area. Dolomitization involves substantial amount of recrystallization. This process is described by the stoichiometric equation: :2 CaCO_3(calcite) + Mg²⁺ ↔ CaMg(CO₃)_2(dolomite) + Ca²⁺ Dolomitization depends on specific conditions which include low Ca:Mg ratio in solution, reactant surface area, the mineralogy of the reactant, high temperatures which represents the thermodynamic stability of the system, and the presence of kinetic inhibitors such as

sulfate The sulfate or sulphate ion is a polyatomic anion with the empirical formula . Salts, acid derivatives, and peroxides of sulfate are widely used in industry. Sulfates occur widely in everyday life. Sulfates are salts of sulfuric acid and many ...

. If the kinetic inhibitors and high temperatures are compatible, then dolomitization can take place in saline environments above thermodynamic and kinetic saturation with respect to dolomite. This type of environment includes, freshwater and seawater mixing zones, normal saline to hypersaline subtidal environments, ''schizohaline'' environments (fluctuating salinity: fresh-water to hypersaline conditions) and hypersaline supratidal environments. When requirements are fulfilled, dolomitization can take place in alkaline environments which are those under the influence of bacterial reduction and

fermentation Fermentation is a metabolic process that produces chemical changes in organic substrates through the action of enzymes. In biochemistry, it is narrowly defined as the extraction of energy from carbohydrates in the absence of oxygen. In food p ...

processes, and areas with high input alkaline continental groundwaters. Environments with high temperatures (about 50 °C) such as subsurface and hydrothermal environments are conducive to dolomitization.

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References

* * * * {{Citation , last = Wilson , first = Edith Newton , last2 = Hardie , first2 = Lawrence A , last3 = Phillips , first3 = Owen M , title = Dolomitization front geometry, fluid flow patterns, and the origin of massive dolomite: the Triassic Latemar buildup, northern Italy , year = 1990 , journal = American Journal of Science , pages = 741–796 , volume = 290 , issue = 7 , doi=10.2475/ajs.290.7.741 , bibcode = 1990AmJS..290..741W Dolomite group Calcite group Geological processes Inorganic reactions Mineralogy Dolomite (rock)

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