| Abstract: | Significant amounts of SO42-, Na+, and OH- are incorporated in marine biogenic calcites. Biogenic high Mg-calcites average about 1 mole percent SO42-. Aragonites and most biogenic low Mg-calcites contain significant amounts of Na+, but very low concentrations of SO42-. The SO42- content of non-biogenic calcites and aragonites investigated was below 100 ppm. The presence of Na+ and SO42- increases the unit cell size of calcites. The solid-solutions show a solubility minimum at about 0.5 mole percent SO42- beyond which the solubility rapidly increases. The solubility product of calcites containing 3 mole percent SO42- is the same as that of aragonite. Na+ appears to have very little effect on the solubility product of calcites. The amounts of Na+ and SO42- incorporated in calcites vary as a function of the rate of crystal growth. The variation of the distribution coefficient (D) of SO42- in calcite at 25.0??C and 0.50 molal NaCl is described by the equation D = k0 + k1R where k0 and k1 are constants equal to 6.16 ?? 10-6 and 3.941 ?? 10-6, respectively, and R is the rate of crystal growth of calcite in mg??min-1??g-1 of seed. The data on Na+ are consistent with the hypothesis that a significant amount of Na+ occupies interstitial positions in the calcite structure. The distribution of Na+ follows a Freundlich isotherm and not the Berthelot-Nernst distribution law. The numerical value of the Na+ distribution coefficient in calcite is probably dependent on the number of defects in the calcite structure. The Na+ contents of calcites are not very accurate indicators of environmental salinities. ?? 1985. |
| Genre: | Article |
| ProdID: | 70012943 |
| Citation Author: | Busenberg, E.; Niel, Plummer, L. |
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| Citation End Page: | 725 |
| Citation Issue: | 3 |
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| Citation Language: | English |
| Citation Larger Work Title: | Geochimica et Cosmochimica Acta |
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| Citation Number Of Pages: | 13 |
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| Citation Search Results Text: | Kinetic and thermodynamic factors controlling the distribution of SO32- and Na+ in calcites and selected aragonites; 1985; Article; Journal; Geochimica et Cosmochimica Acta; Busenberg, E.; Niel, Plummer, L. |
| Citation Start Page: | 713 |
| Citation Volume: | 49 |
| Citation Year: | 1985 |
| Type: | citation/reference |
| Text: | Kinetic and thermodynamic factors controlling the distribution of SO32- and Na+ in calcites and selected aragonites; 1985; Article; Journal; Geochimica et Cosmochimica Acta; Busenberg, E.; Niel, Plummer, L. |
| URL (THUMBNAIL): | http://pubs.er.usgs.gov/thumbnails/outside_thumb.jpg |
| Date Other: | Tue, 1 Jan 1985 00:00 -0600 |
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