Sedimentary Carbonate Minerals

In the following section we briefly discuss some characteristics of sedimentary carbonate minerals. This discussion provides necessary initial information expanded on in later chapters. 

Mineral Formula Fonmla Wt(g) Density (gem3) Crystal 298 System (Jmote 1) ogKjp (calc) togKsp (ret 2) IOC Kgp (Other) 

Cation Ionic Radius Mineral Unit Cell Volume, A  

Hydrated CaCC 3 minerals also are found occasionally in sediments. The occurrence of monoclinic CaC03 6H20 (ikaite) in Antarctic sediments has been 

Monohydrocalcite has been observed rarely in lake sediments and biologic material (Hull and Turnbull, 1973). It generally is found as spherulitic aggregates which may slowly convert to aragonite or calcite. Like ikaite, its formation is favored by low temperatures and high hydrostatic pressures. 

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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. 

Morse JW, Arvidson RS (2002) The dissolution kinetics of major sedimentary carbonate minerals. Earth Sci Rev 58 51-84... 

The carbonate minerals in coals occur primarily as epigenetic fracture fillings (cleat filling). Magnesium, iron, and manganese are often associated with the sedimentary carbonate minerals and would reasonably be expected to be associated with the cleat fillings in coal. 

In this chapter, we introduced the reader to some basic principles of solution chemistry with emphasis on the C02-carbonate acid system. An array of equations necessary for making calculations in this system was developed, which emphasized the relationships between concentrations and activity and the bridging concept of activity coefficients. Because most carbonate sediments and rocks are initially deposited in the marine environment and are bathed by seawater or modified seawater solutions for some or much of their history, the carbonic acid system in seawater was discussed in more detail. An example calculation for seawater saturation state was provided to illustrate how such calculations are made, and to prepare the reader, in particular, for material in Chapter 4. We now investigate the relationships between solutions and sedimentary carbonate minerals in Chapters 2 and 3. 

Dolomite Dolomite is one of the most abundant sedimentary carbonate minerals, yet after years of intense study its mode of formation remains controversial, and its properties under Earth surface conditions are less well known than for most other carbonate minerals. The primary reason for this seems to be that its formation is kinetically hindered by its complex and well-ordered structure. Another problem in understanding dolomite may be as Lynton Land says "there are dolomites and dolomites and dolomites". The topic of dolomite genesis will be dealt with in several later sections of this book. 

In this chapter we will examine the basic chemical concepts of coprecipitation and solid solutions, and the partition coefficients of different elements and compounds in major sedimentary carbonate minerals will be presented. A brief summary of information on oxygen and carbon isotope fractionation in carbonate minerals will also be presented. A major portion of this chapter is devoted to... 

Land (e.g., 198S) has stressed the chemical and structural variations associated with natural dolomites, and has gone so far as to suggest that the name "dolomite" be used in the same way that the mineral name "feldspar" is used. The fact that dolomite is relatively unreactive compared to most other sedimentary carbonate minerals has severely limited experimental studies under temperature and pressure conditions that exist during shallow burial. Consequently, most information on the chemical behavior of dolomite must be obtained from observations of complex natural systems. Such observations are all too often open to multiple interpretations. 

Lippmann F. (1973) Sedimentary Carbonate Minerals. Springer-Verlag, New York, 228pp. 

Lippmann, F. Sedimentary Carbonate Minerals Springer-Verlag New York, 1973, p 228. 

F. Lippmann, Sedimentary Carbonate Minerals, 1st edn., Springer-Verlag, Berlin, 1973,... 

Dolomite. A sedimentary carbonate mineral, of the formula CaMg(C03)2, generally thought to be formed from limestone by the replacement of Ca with Mg. 

Morse JW, Arvidson RS (2002) The dissolution kinetics of major sedimentary carbonate minerals. Earth Sci Rev 58(l-2) 51-84 Nishikawa T, Tarutani K, Yamamoto T (2009) Nitrate and phosphate uptake kinetics of the harmful diatom Eucampia zodiacus Ehrenberg, a causative organism in the bleaching of aquacultured Porphyra thalli. Harmful Algae 8(3) 513-517... 

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