How does dolomite form

Lime kiln: Dolomite and limestone have been heated in kilns to produce lime for thousands of years. It was built in for the production of lime. National Park Service photo. Dolomite and limestone are used in similar ways. They are crushed and used as an aggregate in construction projects.

They are kiln-fired in the manufacture of cement. They are cut into blocks and slabs for use as a dimension stone. They are calcined to produce lime. In some of these uses, dolomite is preferred. Its greater hardness makes it a superior construction material. Its lower solubility makes it more resistant to the acid content of rain and soil. The dolomitization process results in a slight volume reduction when limestone is converted into dolomite. This can produce a porosity zone in the strata where dolomitization has occurred.

These pore spaces can be traps for subsurface fluids like oil and natural gas. This is why dolomite is often a reservoir rock that is sought in the exploration for oil and natural gas.

Dolomite can also serve as a host rock for lead , zinc , and copper deposits. In the chemical industry, dolomite is used as a source of magnesia MgO. The steel industry uses dolomite as a sintering agent in processing iron ore and as a flux in the production of steel. In agriculture, dolomite is used as a soil conditioner and as a feed additive for livestock.

Dolomite is used in the production of glass and ceramics. It is the primary constituent of dolomite rock dolostone and dolomarble. It is similar to the most common carbonate mineral calcite. These two share some similarities in structure and are very closely related chemically. It means that half of the calcium in the structure of calcite is replaced by the magnesium in dolomite.

However, there is no solid solution between the two because calcium and magnesium ions have different size and hence can not replace each other directly in the crystal structure. Dolomite may be the sole or primary constituent of marble. Dolomarble from Fauske, Norway.

Width of sample 14 cm. Dolostone is the most important rock type that is composed mostly of it. Dolostone was probably originally limestone which was altered by Mg-bearing water circulating in the rocks. Dolomite does not precipitate out of aqueous solutions like calcite does in normal circumstances.

Carbonate rock is dolostone if at least 50 percent of it is dolomite. In Earth's history, several such oxygen-free periods have occurred, partly consistent with time periods of intensified dolomite deposition. Note: Content may be edited for style and length. Science News. Journal Reference : S. Krause, V. Liebetrau, S. Gorb, M. Sanchez-Roman, J. McKenzie, T. Dolomite can also form in lakes, on or beneath the shallow seafloor, in zones of brine reflux, and in early to late burial settings.

It may form from seawater, from continental waters, from the mixing of basinal brines, the mixing of hypersaline brine with seawater, or the mixing of seawater with meteoric water, or via the cooling of basinal brines. Dolomitization also creates new crystals, with new rhomb growth following the dissolution of less stable precursors.

Dolomitization model and formation depend on the source dolomitization site and lastly, there must exist a favorable condition for a chemical reaction. One particular type of dolomite which may be a cement or a replacement is baroque dolomite, also called 'saddle' or 'white sparry' dolomite and known to mineral collectors as pearl spar.

It is characterized by a warped crystal lattice. Carbonate rocks are a class of sedimentary rocks composed primarily of carbonate minerals. The two major types are limestone, which is composed of calcite or aragonite different crystal forms of CaCO 3 and dolostone, which is composed of the mineral dolomite CaMg CO 3 2.

Carbonate rocks are depositionally most simple but diagenetically most complex rocks of the world. There are a number of carbonate minerals which are formed by combining of one or more ion with the CO 3 2- ion. Dolomite is an anhydrous carbonate mineral composed of calcium magnesium carbonate, ideally CaMg CO 3 2.

The term is also used for a sedimentary carbonate rock composed mostly of the mineral dolomite. An alternative name sometimes used for the dolomitic rock type is dolostone. Dolomite is an unusual carbonate mineral. It is common in ancient platform carbonates, yet it is rare in Holocene sediments Table 1.

On the basis of the mode of formation, dolomites can broadly be divided into two groups: primary dolomite and secondary dolomite. The widely accepted hypothesis of dolomitization is that limestone is transformed into dolomite by the dissolution of calcite followed by dolomite precipitation. Dolomite is formed by the replacement of the calcite ions by the magnesium ions.

Depending upon the ratio of the Mg ions in the crystal lattice they have different names Figure 1. Modern dolomite formation has been found to occur under anaerobic conditions in supersaturated saline lagoons in Brazil. Primary dolomite is indeed infrequent and often forms in lakes and lagoons while most of dolomite is from the replacement origin. Dolomite is in fact formed in high intertidal supratidal and sabkhas environment.

Dolomitic that formed in the supratidal environment are precipitated from evaporated sea water. This process comprises the formation of dolomitizing solutions over vaporization of lagoon water or tidal flat pore water besides then the succession of these solutions into nearby carbonate rocks Figure 3. This type of dolomite formed by the mixing of seawater with the fresh water.

The source of water may be rainwater Figure 4. Burial dolomitization involves prime mechanism which is the dewatering of basinal mud rocks due to compaction and removal of Mg-rich fluids into neighboring shelf edge. Expulsion of water and changes of clay minerals with enlarged burial and increasing temperature suggest that it would liberate Mg ions along with Fe ion.

The diagenesis of basinal shales are generally organic-rich and the diagenesis would contribute to CO 3 ions. Seawater itself can also be a source of dolomite because it contains the sufficient amount of Mg ions with little modification if a good pumping process exists.

Dedolimitization refers to the partial to the whole transformation of former dolomite rocks to a calcian rich rock. The dolomitization can be considered as a kind of process in which Mg is gradually released. The dedolomitization process can be divided into two steps,.