Dolomites dissolution kinetics

Recently, Chou et al. (1989) studied the dissolution kinetics of various carbonate minerals in aqueous solution. Figure 2.10 illustrates the experimental results for aragonite, calcite, witherite, dolomite, and magnesite. These data can be fit by rate equations, an example of which is shown in equation 2.28 for calcite. 

TABLE 7.1. Specific Surface Area and Acid-Dissolution Kinetic Parameters of Calcite, Dolomite, and Limestone Samples... 

Herman, J. S., and W. B. White. 1985. Dissolution kinetics of dolomite Effects of lithology and fluid flow velocity. Geochim. Cosmochim. Acta 49 2017-26. 

The rates of dissolution of various carbonates were studied in [200], The kinetics of magnesite dissolution was studied in [201] and that of dolomite dissolution in [202,203],... 

To convert calciiun carbonate to dolomite, some of the calcium must have been replaced by magnesiiun, requiring the partial dissolution of the carbonate. This process is promoted by contact with acidic pore water, such as occurs in organic-rich sediments because remineralization produces carbon dioxide. This is probably why dolomites are presently forming in detrital algal mats buried beneath sabkhat. The restricted extent of these modern dolomites reflects a kinetic hindrance to precipitation. Apparently dolomite precipitation in this setting is too slow to form substantial deposits when sea level is rapidly fluctuating. 

Many natural aquatic systems have a chemical composition close to saturation with respect to calcite or even dolomite. This is the case, for instance, for seawater, which is usually slightly oversaturated in the upper part of the water column and slightly undersaturated at greater depths. Under these conditions, the rates of both precipitation and dissolution contribute significantly to the overall rate of reaction. Even though the reaction paths may be very complex, there is a very direct and important link between the kinetic rate constants, according to which the rates of forward and reverse microscopic processes are equal for every elementary reaction. The fundamental aspect of this principle forms the essential aspect of the theory of irreversible thermodynamics (Frigogine, 1967). 

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