Surface complexation clues to dolomite growth
- Sandia National Labs., Albuquerque, NM (United States)
Calcium and magnesium adsorb in near-stoichiometric proportions to dolomite over wide ranges in [Ca{sup 2+}]/[Mg{sup 2+}], ionic strength, and solution composition pointing to minimal mixing of metal cations between the CaCO{sub 3} and MgCO{sub 3} layer edges exposed at the dolomite surface. Near-neutral pH Mg and Ca adsorb as hydrated ions, or, in sulfate-rich solutions, as metal sulfate complexes. Near-stoichiometric adsorption of Ca and Mg points to dehydration and subsequent carbonation of adsorbed Mg as the likely rate-limiting step for dolomite growth at near-Earth surface conditions. We propose that one path for dolomite growth from low-temperature natural waters is through the initial adsorption of Mg-sulfate complexes onto either (1) growing dolomite crystals or (2) rate-limiting dolomite nucleii. Field relations, as well as homogeneous synthesis at low temperatures (25{degrees}C < T < 100{degrees}C) support this hypothesis and provide a mechanistic explanation for dolomite growth from sulfate-rich natural waters. 36 refs.
- Research Organization:
- Sandia National Laboratories (SNL), Albuquerque, NM, and Livermore, CA (United States)
- DOE Contract Number:
- AC04-94AL85000
- OSTI ID:
- 530429
- Journal Information:
- Geochimica et Cosmochimica Acta, Vol. 60, Issue 4; Other Information: PBD: Feb 1996
- Country of Publication:
- United States
- Language:
- English
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