Carbonate precipitation marine

Sholkovitz ER, Elderfield H, Szymczak R, Casey K (1999) Island weathering riverine sources of rare earth elements to the western Pacific Ocean. Marine Chem 68 39-57 Skulan JL, Beard BL, Johnson CM (2002) Kinetic and equilibrium Fe isotope fractionation between aqueous Fe(III) and hematite. Geochim Cosmochim Acta 66 2995-3015 Sumner DY (1997) Carbonate precipitation and oxygen stratification in Late Archean seawater as deduced from facies and stratigraphy of the Gamohaan and Frisco Formations, Transvaal Supergroup, South Africa. Am J Sci 297 455-487... 

The most complete study of the inhibition of calcium carbonate precipitation by organic matter was carried out by Berner et al. (1978), where primary concern was the lack of carbonate precipitation from supersaturated seawater. Both synthetic organic compounds and organic-rich pore waters from Long Island Sound were used to measure the inhibition of aragonite precipitation. Natural marine humic substances and certain aromatic acids were found to be the strongest inhibitors. The rate of precipitation in pore waters was also found to be strongly inhibited. 

An extensive literature exists on the occurrence of early carbonate precipitates in marine sediments, where they are generally termed cements. Included in this literature are books devoted solely to carbonate cements (e.g., Bricker, 1971 Schneidermann and Harris, 1985) and numerous reviews (e.g., Milliman, 1974 Bathurst, 1974, 1975 Harris et al 1985). Many investigations have been largely descriptive in nature, focusing primarily on the distribution, mineralogy, and morphology of the cements. Here we will briefly summarize the major aspects of these observations, and we will concentrate on the chemical aspects of the formation of these precipitates. 

This sulfate reduction reaction in anoxic carbonate sediments has potential importance for carbonate dissolution in shallow-water, marine environments, but its global significance remains a question. An observation of interest is that even complete sulfate reduction returns the saturation state of the water to only about half its original value. Thus the sulfate reduction reaction by itself may not promote carbonate precipitation and partial sulfate reduction may result in carbonate dissolution. 

One major paper attacking the problem of the relationship between the preservation of calcium carbonate in shallow anoxic marine sediments and their chemistry was by Aller (1982). The study was conducted at sites in Long Island Sound. The calcium carbonate content of the sediments decreased with increasing water depth. At the shallow FOAM (Friends of Anaerobic Muds) site shell layers associated with storms resulted in irregular variations in the carbonate content of the sediment. Ca2+ loss from the pore waters, indicative of calcium carbonate precipitation, was found only at the FOAM site below -20 cm depth. During the winter, elevated Ca2+ to CL ratios were observed near the sediment-water interface... 

One of the primary aims in the study of the geochemistry of carbonates in marine waters is the calculation of the saturation state of the seawater with respect to carbonate minerals. The saturation state of a solution with respect to a given mineral is simply the ratio of the ion activity or concentration product to the thermodynamic or stoichiometric solubility product (Equation (3)). In seawater the latter is generally used and Hmingjai is the symbol used to represent the ratio. If H = 1, the solid and solution are in equilibrium if H < 1, the solution is undersaturated and mineral dissolution can occur, and if H > 1, the solution is supersaturated and precipitation should... 

Arvidson R. S., Mackenzie F. T., and Guidry M. W. (2000) Ocean/atmosphere history and carbonate precipitation rates a solution to the dolomite problem. In Marine Authigenesis from Global to Microbial, SEPM Spec. Publ. No. 65 (eds. C. R. Glenn, L. Prevot-Lucas, and J. Lucas), SEPM, Tulsa, pp. 1-5. 

Carbonate precipitation controlled by photosynthetic CO2 assimilation is a major process in lakes and in the formation of travertines. However, in the marine environment carbonate precipitation is influenced by many processes and in only a few instances has been shown to be the direct result of photosynthetic CO2 assimilation. On the other hand, photosynthesis is a major factor in the natural carbonate cycle and controls the total carbonate equilibrium to the extent that a constant ratio between organic-C and carbonate-C is maintained in sediments even though little direct precipitational relation can be established between the two. 

Shinano, H. and Sakai, M., 1969. Studies of marine microorganisms taking part in the precipitation of calcium carbonate. I. Calcium carbonate precipitation in peptone medium prepared with seawater and artificial seawater. Bull. Jpn. Soc. Sci. Fisheries, 35 1001—1969. 

Fig. 2.3.2. Comparison of the range in carbon isotopic composition for hermatypic corals, ahermatypic corals, and marine carbonate precipitated in isotopic equilibrium with the COj" — HCO5 — CO2 system of ambient seawater. All of the corals (111 hermatypes and 59 ahermatypes) were collected from shallow-water, reef surface environments at Heron Island, Australia. The length of the horizontal bars is equivalent to the mean one standard deviation (Weber, 1974).

In order to understand the formation of beachrock, some fundamentals of the marine carbonate system (C02-H20-CaC03) and calcium carbonate precipitation and dissolution have to be considered. Only limited aspects of the subject can be discussed here as the topic is complex and treated at length in various textbooks (e.g. Lippmann, 1973 Berner, 1980 Morse and Mackenzie, 1990). 

Cleveland, W. S., T. E. Graedel, and B. Kleiner (1977). Urban formaldehyde observed correlation with source emissions and photochemistry. Atmos. Environ. 11, 357-360. Cloud, P. E. (1965). Carbonate precipitation and dissolution in the marine environment. Chemical Oceanography" (J. P. Riley and G. Skirrow, eds.), Vol. 2, Chap. 17, pp. 127-158. Academic Press, New York. 

Although calcareous plankton presently dominate marine carbonate precipitation,... 

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