Calcium and Magnesium Hydroxide Precipitation from Alkaline Groundwaters in Oman, and Their Significance to the Process of Serpentinization

Colin Neal and Gordon Stanger
Institute of Hydrology, Maclean Building, Crowmarsh Gifford, Wallingford, Oxon. OX10 8BB
Department of Earth Sciences, The Open University, Walton Hall, Milton Keynes, MK7 6AA

Abstract: The occurrence and genesis of Ca(OH)2 and Mg(OH)2 deposits associated with hyperalkaline groundwater from partly serpentinized ultramafic rocks in Northern Oman is reported. Two types of Ca(OH)2 deposit are differentiated; crystalline portlandite formed by the evaporation of Ca2+-2OH spring waters, and a form of amorphous gel, not previously known in nature. The latter is a product of present-day low-temperature serpentinization. Mg(OH)2 (brucite) in both holocrystalline and gel forms is produced by mixing of Mg2+−2HCO3− surface waters with a Ca2+-2OH groundwater in both surface and groundwater environments. These results indicate that significant differences exist between the processes of medium- and low-temperature brucite generation.

Mineralogical Magazine; June 1984 v. 48; no. 347; p. 237-241; DOI: 10.1180/minmag.1984.048.347.07
© 1984, The Mineralogical Society
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