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The partition coefficient for Ba2+ into calcite has been established as 0.06 ± 0.01 at 25°C (77°F). The partition coefficient proved independent of rate of precipitation in a series of 19 runs of varying duration. This value is substantially lower than that reported by Kitano in 1971, reflecting our seeding technique, which focused the experiment on crystal growth rather than on spontaneous nucleation and growth. The 0.06 value is compatible with the values reported for Sr2+ (0.05 to 0.14), a cation of identical charge, but closer to Ca2+ in ionic radius.
The natural partitioning of Ba2+ was examined in fresh (aragonite) and altered (calcite) corals from the Pleistocene reef terraces exposed on Barbados, West Indies. The Ba2+ concentrations ranged from 8 to 15 ppm in the aragonites and decreased to typical values of 1 to 3 ppm in the calcites. The partitioning of Ba2+ in these samples was quantitatively similar to the attendant partitioning of Sr2+. The partitioning of Ba2+ during the carbonate cycle offers new areas of investigation. The low concentrations of Ba2+ in sedimentary biograins (3 orders of magnitude less than Sr2+) make Ba2+ a sensitive monitor of externally derived, barium-bearing solutions involved in diagenetic reactions. Likewise, t e low concentrations ensure ideal partitioning behavior in diagenetic solutions of low ionic strength.
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