1981 Edition

Anhydrite and gypsum

Reference work entry
DOI: https://doi.org/10.1007/0-387-30720-6_7

The calcium sulfate in evaporites sometimes occurs as gypsum, CaSO4 · 2H2O, sometimes as anhydrite, CaSO4, and sometimes as both minerals together. Near-surface material is almost always gypsum because of the ease of weathering and hydration of CaSO4, and deep-seated subsurface material is always anhydrite because of dehydration effects. Numerous examples of replacement of one of these minerals by another are known (Murray, 1964; Stewart, 1953; Borchert and Baier, 1953; Ogniben, 1955; Sund, 1959).

The water solubilities of gypsum and anhydrite have been investigated by Posnjak (1938), Bock (1961), Marshall and Slusher (1966), and others; and MacDonald (1953) has made thermochemical calculations. For many years, it was believed that gypsum crystallized out of pure water at a temperature less than about 40°C, that anhydrite was the stable phase above this temperature, and that increasing salinity lowered the transition point (see Fig. 1).
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  1. Anderson, R. Y., and Kirkland, D. W., 1966. Intra basin varve correlation, Geol. Soc. Am., Bull., 77, 241–256.Google Scholar
  2. Bock, E., 1961. On the solubility of anhydrous calcium sulfate and of gypsum in concentrated solutions of sodium chloride at 25°C, 30°C and 50°C, Canadian J. Chem., 39, 1746–1751.CrossRefGoogle Scholar
  3. Borchert, H., and Baier, E., 1953. Zur metamorphose ozeaner Gipsablagerungun, Neues Jahrb. Mineral. Abh., 86, 103–154.Google Scholar
  4. Cruft, E. F., and Chao, P. C., 1969. Kinetic considerations of the gypsum-anhydrite transition, 3rd Internat. Salt Symp., Cleveland, Ohio.Google Scholar
  5. Davidson, C. F., 1965. A possible mode or origin of stratabound copper ores, Econ. Geol., 60, 942–954.CrossRefGoogle Scholar
  6. Hardie, L. A., 1967. The gypsum-anhydrite equilibrium at one atmosphere pressure, Am. Mineralogist, 52, 171–200.Google Scholar
  7. MacDonald, G. J. F., 1953. Anhydrite-gypsum equilibrium relationships, Am. J. Sci., 251, 884–898.CrossRefGoogle Scholar
  8. Marshall, W. C., and Slusher, R., 1966. Thermodynamics of calcium sulfate dihydrate in aqueous sodium chloride solutions, 0–110°, J. Phys. Chem., 70, 4015–4028.Google Scholar
  9. Murray, R. C., 1964. Origin and diagenesis of gypsum and anhydrite, J. Sed. Petrology, 34, 512–523.Google Scholar
  10. Ogniben, L., 1955. Inverse graded bedding in primary gypsum of chemical deposition, J. Sed. Petrology, 25, 273–281.Google Scholar
  11. Posnjak, E., 1938. The system CaSO4-H2O, Am. J. Sci., 238, 559–568. CrossRefGoogle Scholar
  12. Stewart, F. H., 1953. Early gypsum in the Permian evaporites of Northeastern England, Proc. Geol. Assoc. Yorks., 64, 33–39.Google Scholar
  13. Sund, J. O., 1959. Origin of the New Brunswick gypsum deposits, Canadian Mining Metall. Bull., 52, 707–712.Google Scholar
  14. Zen, E. An., 1965. Solubility measurements in the system CaSO4-NaCl-H2O at 35°, 50° and 70° and 1 atm pressure, J. Petrology, 6, 124–164.Google Scholar

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© Hutchinson Ross Publishing Company 1981