Chemistry dolomite

Fluxes are usually added in the form of either limestone or dolomite. The fluxes provide the basic constituents (CaO and MgO) needed to balance the acid constituents (Si02 and AI2O2) from the coke and ore. These are the four primary oxides which form the slag, although minor amounts of other oxides such as MnO, Na20, K2O, P2 S Ti02, and sulfur are also present. Proper adjustment of the slag chemistry is necessary to obtain the desired... 

Since we have no direct information about the chemistry of the Fountain fluid, we assume that its composition reflects reaction with minerals in the evaporite strata that lie beneath the Lyons. We take this fluid to be a three molal NaCl solution that has equilibrated with dolomite, anhydrite, magnesite (MgCC>3), and quartz. The choice of NaCl concentration reflects the upper correlation limit of the B-dot (modified Debye-Hiickel) equations (see Chapter 8). To set pH, we assume a CO2 fugacity of 50, which we will show leads to a reasonable interpretation of the isotopic composition of the dolomite cement. 

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

Dolomite is one of the most abundant sedimentary carbonate minerals but its mode of formation and its surface properties are less well known than for most other carbonate minerals. As we have mentioned, the nucleation of dolomites and its structural ordering is extremely hindered. There is a general trend for the "ideality" of dolomite to increase with the age of dolomite over geological time (Morse and Mackenzie, 1990). Most dolomites that are currently forming in surfacial sediments and that have been synthesized in the laboratory are calcium-rich and far from perfectly ordered. Such dolomites are commonly referred to as "protodolomites . Morse and Mackenzie (1990) have reviewed extensively the geochemistry (including the surface chemistry of dolomites and Mg-calcites. 

Croal LR, Johnson CM, Beard BL, Newman DK (2004) Iron isotope fractionation by anoxygenic Fe(II)-phototrophic bacteria. Geochim Cosmochim Acta 68 1227-1242 Curtis CD, Coleman ML, Love LG (1986) Pore water evolution during sediment burial from isotopic and mineral chemistry of calcite, dolomite and siderite concretions. Geochim Cosmochim Acta 50 2321-2334... 

The most important feature of mineral chemistry in carbonates of Chehelkureh deposit is the large range in the FeCOsiMgCOs ratio which can indicate large variations in chemistry of hydrothermal fluids. Compositions extend along the magnesite-siderite join, from 22 to 72 mole% FeCOs (Fig. 3). Dolomite and ankerite compositions extend between 0 to 27 mole% FeCOs. 

Bodies of Water and the Chemical Sediments ,— The chemistry of the deposition of salts from sea-water has already been made the subject of special research, and van t Hoff s results in this field are already familiar. The deposition of calcium carbonate awaits a similar thorough study. Allied questions are the formation of dolomite, the deposition of various salts from inclosed bodies of water, the deposition of phosphate rocks, the precipitation of colloidal suspensions of clay and other substances, and the origin of the great deposits of sedimentary iron ore. 

Table X gives data for two elements whose equilibrium chemistry in sea water has been investigated by many workers. Although some important questions, such as the solubility of dolomite, are still open, the numbers given are probably more reliable than those in Tables VIII and IX.

Calcium Carbonate and Dolomite. We may consider gross chemistry of the lakes constant over temperature, pH, and Pco2 changes which... 

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,... 

To understand the process of formation of these organogenic dolomites, it is necessary to look at the chemistry of the pore waters in which they form. Figure... 

Machel H.G. and Mountjoy E.W. (1986) Chemistry and environments of dolomitization - A reappraisal. Earth-Science Reviews 23, 175-222. 

Morrow D.W. (1982a) Diagenesis 1. Dolomite—Part 1. The chemistry of dolomitization and dolomite precipitation. Geoscience Canada 9,5-13... 

Wood J.R. (1987) A model for dolomitization by pore fluid flow. In Physics and Chemistry of Porous Media II (eds. J.R. Banavar, J. Koplik and K.W. Winkler), pp. 17-36. Amer. Inst. Physics Proceedings 154, Amer. Inst. Physics, New York. 

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