Sediment calcite content

Calcite content of surface sediments in wt%. Source From Seiter, K., et al. (2004). Deep-Sea Research, 52, 2001-2026. (See companion website for coior version.)... 

The ultimate fate of much of the CO2 released to the atmosphere through the burning of coal, oil, and natural gas will be to react with the CaC03 stored in marine sediments (Broecker and Takahashi, 1977 Sundquist, 1990 Archer et al., 1997). The amount of CaC03 available for dissolution at any given place on the seafloor depends on the calcite content in the sediment... 

The mineral calcite is one of the most prominent phases in deep sea sediments. Its distribution with water depth on the flanks of the oceanic ridges everywhere in the world oceans has the same basic character. Sediments with uniformly high calcite content extend from the crest down the ridge flank to what Berger (1968) has teimed the lysocline. Here a decrease in calcite content with water depth commences. This decrease continues imtil sediments nearly free of calcite are encountered. Below this horizon (often referred to as the calcite compensation depth) the sediments are free of calcite. Although the pattern is everywhere the same the depth of the lysocline and the width of the transition zone (i.e. distance between lysocline and compensation depth) vary from basin to basin (see Fig. l). 

Thus, larger solid/water ratios such as are encountered in pore waters of sediments lead to smaller MgC(>3 contents in the equilibrium magnesian calcites although in either case the magnesium content of the solid increases. Wollast and Reinhard-Derie presented data to support the theory from the standpoint of dissolution and some of our results for the precipitation case... 

The occurrence of kaolinite is generally erratic but in the terrigenous sediments (Muffler and White, 1969) it can apparently react with dolomite to form the assemblage calcite + chlorite between 120-180°C. Expandable chlorite was noted in shear zones, and iron-rich chlorite is common in most of the rocks becoming more evident at greater depths. In the terrigenous rocks observed, the apparent alumina content of chlorite decreases with depth. Alkali zeolites have been observed at temperatures up to 100°C in the deeply buried rocks. 

Transport by Calcite. The annual flux of calcite into the uppermost trap (29 m below the lake surface) was estimated to be 35 g/m2, and the mean measured P content of this phase was estimated at 1.05 mg/g. A comparison of the calculated 29-m P flux, 37 mg/m2, with estimates of deposition to bottom sediment, indicated that 5-16 mg/m2 (13-43% of upper-water-column flux) was returned to the water column. This relatively small regeneration flux was not detected in profiles of meta- and hypolimnetic... 

It should be kept in mind that, in spite of these major variations in the CO2-carbonic acid system, virtually all surface seawater is supersaturated with respect to calcite and aragonite. However, variations in the composition of surface waters can have a major influence on the depth at which deep seawater becomes undersaturated with respect to these minerals. The CO2 content of the water is the primary factor controlling its initial saturation state. The productivity and temperature of surface seawater also play major roles, in determining the types and amounts of biogenic carbonates that are produced. Later it will be shown that there is a definite relation between the saturation state of deep seawater, the rain rate of biogenic material and the accumulation of calcium carbonate in deep sea sediments. 

Figure 4.25. Distribution of Mg contents of magnesian calcite cements in marine sediments. (After Mucci, 1987.)...

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