Calcite, formation

An example of a speciation calculation involving calcite formation is shown in Table 3.1 for a soil solution containing the same metals and ligands as in the example in Table 2.6, but at pH 7.9 instead of 5.6. The nominal total concentration of Ca (5.25 mol m 3) is predicted to be partitioned as 56% calcite and 44% aqueous species at equilibrium. Thus the solubility of Ca is predicted to be 2.3 mol m 3 (-- 0.44 x Ca,) under the conditions of the calculation. Note that about 12% of this solubility is contributed by metal-ligand complexes. As an additional hit of analysis, the IAP for calcite, (Ca2 )(C()2 ), in the soil solution can be calculated, given the values of the concentrations of Ca-, ... 

Undoubtedly, the site named as locality no. 3 is the richest of all the Villany faunas. Kormos called this locality Villany-Kalkberg-Nord (Picture 6). The site is situated on the northern wall of the eastern end of the ridge quarry. A cleft, on the average 1 m wide and lying in a direction east to west, cuts through the Lower Malm Oxfordian limestone, and is filled with red sediment cemented by secondary calcite formation. 

Extensive seeded calclte growth experiments in the presence of phosphate ion indicate that the phosphate ion adsorbs onto the crystal surface as a monolayer. At a concentration of 10" M, phosphate ion can strongly inhibit calcite formation however, short term experiments show that this monolayer adsorption removes insignificant amounts of phosphorus from solution. In experiments lasting several days a further decrease in solution phosphate concentration occurs, presumably caused by nucleation of a surface calcium phosphate phase on the calcite seed. 

Blomqvist R., Vuorela P., Nissinen P., Ruskeeniemi T., Frape S. K., and Ivanovich M. (1993) Crustal rebound-related groundwater flow and calcite formation in the crystalline bedrock of the Fennoscandian shield new observations from Finland. Extended Abstract for the OECD Meeting, Workshop on paleohydrogeological methods and their applications for radioactive waste disposal, 5p. 

In order to illustrate the structural-chemical features of calcification, two biological systems, namely, calcite and aragonite crystals in inner-ear gravity devices and calcite formation in a marine unicellular alga, Emiliania huxleyi, will be reviewed. 

Wada, N., Yamashita, K., and Umegaki, T. (1999). Effects of carboxylic acids on calcite formation in tlie presence of Mg- ions. J. Colloid Interface Sci. 212, 357-364. 

Lower Cretaceous Mannville Group (Alberta, Canada) resulted from biodegradation of petroleum, involving a bacterial fermentation step. Whether a similar scenario can be invoked for the Oseberg calcite is arguable, considering the temperature of calcite formation (90-100°C), which approaches the upper limit for bacterial activity. It is, however, consistent with the early biodegradation of petroleum in the Alpha structure documented by Dahl Yukler(1991). 

Alt and Shanks (in prep) have investigated stable isotope systematics and serpenti-zation processes in these rocks. There are a few late carbonate veins that have 5 C from l.l-4.5%o and from 7.9-34.1 %o. These values indicate calcite formation at... 

Kitano, Y., Okumara, M. and Idogaki, M. (1980) Abnormal behaviours of copper and zinc ions in parent solution at the early stage of calcite formation. Geochemical Journal, 14, 167-175. 

These variations can be explained by the Ti02 photocatalytie action for the mixtures with nano-titania the latter leads both to calcite formation and enhanced hydration of CSH and CAH products, similar to what was observed... 

The precipitations of CaCOs in the presence of the G3.5 PAMAM dendrimer were also carried out imder the same conditions. The results are siunmarized in Table 5. No calcite formation was observed in all the concentrations. As the generation number of the anionic PAMAM dendrimer increased from G1.5 to G3.5, the particle sizes of the spherical vaterite de-... 

Akagi, T., and Kono, Y. (1995). Inhibiting Effects of Lanthanum Ions on Calcite Formation from CaCl2-NaHC03 Solutions at 25°C. Aquatic Geochem. 1(2), 231-239. 

Tomiyama, C., and Kitano, Y. (1984). Calcite Formation in Calcium Chloride-Rich Water. Jpn. J. Limnol. 45(1), 1-5. 

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