Dolomite, formation

The only fluid, common to oil field operations, that has a significant interaction with TKPP solutions was concentrated calcium chloride. Solutions of calcium chloride, spent acid, are generated during the acidization of a limestone or a dolomite formation. When solutions containing 10% calcium chloride were mixed in equal proportions with 14.5 ppg TKPP solutions, massive precipitation occurred. Similar precipitation was observed with oil field brines having calcium concentrations above 400 ppm. 

Carpenter, A. B., 1980, The chemistry of dolomite formation I the stability of dolomite. Society of Economic Paleontologists and Mineralogists Special Publication28,111-121. 

The precipitation of protodolomite under 100°C. from solutions of calcium and magnesium chlorides has been reported, and it seems plausible to suggest that, given sufficient time, dolomite would result from recrystallization of protodolomite. Siegel (35) found that protodolomite was produced at 25 °C. when calcium and magnesium ions were entrapped in activated charcoal and could react with carbonate ion at a low rate he also found that sulfate ion was involved in dolomite formation. 

Thornburg, K. and Sahai, N. (2004) Arsenic occurrence, mobility, and retardation in sandstone and dolomite formations of the Fox River valley, eastern Wisconsin. Environmental Science and Technology, 38(19), 5087-94. 

Microbial metabolic activity in general is known both to accelerate transitions to stable equilibria and to produce metastable intermediate dissolved species and mineral precipitates that otherwise would not exist or would not be abundant. In general, most metabolic schemes that intervene in the existence and abundance of one anionic species or complex will do so with others, too, and this also has a big effect on the evaporitic and freezing chemistry dealt with by FREZCHEM. For example, dolomite formation is linked to sulfate reduction in one biogeochemical scheme. Lacking microbial activity,... 

Sanchez-Roman M, McKenzie JA, Vasconcelos C, Rivadenyra M (2005) Bac-terially induced dolomite formation in the presence of sulfate ions under aerobic conditions. AGU Fall Meeting, Abstract B13A-1041... 

General considerations The "dolomite problem" has been one of the most intensely studied and debated topics in geology. The "problem is that modem marine sediments contain only relatively rare and minor occurrences of this mineral, whereas it is a major component of sedimentary rocks. Questions about whether major dolomite formation from seawater could have occurred in the geologic past, the conditions necessary for dolomite formation, and many other aspects of the "dolomite problem" have resulted in a voluminous literature that includes entire books devoted to the topic (e.g., Zenger et al., 1980 Zenger and Mazzullo, 1982). The literature on dolomite formation is typified by the vigor with which contending hypotheses are supported and attacked. Many of the controversies have stemmed from attempts to find "the answer" to how sedimentary dolomite forms. 

Under the modest temperature and pressure conditions characteristic of the environments in which meteoric diagenesis typically takes place, many of the most important reactions are slow. This has severely constrained the study of the chemical mechanisms and kinetics involved in such fundamental processes as the aragonite to calcite transformation and dolomite formation. Information on these processes obtained under conditions not typical of the meteoric realm (e.g., elevated temperatures) are of questionable applicability to "real world" carbonate diagenesis. 

The timing of the dolomitization of carbonate rock bodies and emplacement of dolomite cements has been one of the more controversial aspects of the "dolomite problem." Most of the basic factors controlling dolomite formation, where were discussed in Chapters 6 and 7, also apply to dolomite formation during the later stages of diagenesis. However, the extended periods of time, the solution compositions likely to be encountered, and the elevated temperature and pressure that occur during deep burial provide highly favorable conditions for dolomite formation. 

Clay mineral diagenesis also may play a role in dolomite formation during burial. The commonly observed conversion of smectites to illite can result in the release of the magnesium necessary for dolomite formation (e.g., McHargue and Price, 1982). Dolomite formation is observed near and within shale beds however, this process again appears to be a localized mechanism and probably is incapable of producing large quantities of dolomite. 

When carbonates are absent from the original sediments, the pore waters supply the necessary Ca2+, Mg2+ and CO32- for trace amounts of dolomite formation ... 

A more sophisticated chemical understanding needs to be obtained of the problem of why elevated ionic strength seems to influence so many important reactions such as the aragonite to calcite transformation and dolomite formation. 

Compton J.S. and Siever R. (1986) Diffusion and mass balance of magnesium during early dolomite formation, Monterey Formation. Geochim. Cosmochim. Acta 50, 125-135. 

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