Determination of the solubility products of sodium carbonate minerals and an application to trona deposition in Lake Magadi (Kenya) - Université Toulouse 3 Accéder directement au contenu
Article Dans Une Revue Geochimica et Cosmochimica Acta Année : 1984

Determination of the solubility products of sodium carbonate minerals and an application to trona deposition in Lake Magadi (Kenya)

Résumé

The ion-interaction model of PITZER (1973), is very effective in deriving stability relationships at high concentrations for the system Na - Cl - HCO 3 - CO 3 - OH - H 2 O . The solubility products of the main sodium carbonates have been calculated from solubility data between 5 and 50°C. The stability diagram in log p co2 -- temperature coordinates and the invariant points deduced from the newly determined data are in good agreement with the most recent measurements. These results are used to calculate the activities of the major dissolved species in Lake Magadi brines (Kenya). The thermodynamic treatment confirms the main conclusions reached earlier by Eugster (1970, 1980) mainly from field observations. Trona precipitation occurs at equilibrium while natron is likely to form when the temperature decreases below 25°C. After the salt deposition the CO 2 supply from the atmosphere is too slow to allow equilibrium between the atmosphere and the brines. In the next stages of evaporative concentration thermonatrite and halite precipitate. The deposition of the latter salts along with the observed HCO - 3 depletion suggest that fractional crystallization is likely to control trona deposition.

Dates et versions

hal-00663050 , version 1 (25-01-2012)

Identifiants

Citer

Christophe Monnin, Jacques Schott. Determination of the solubility products of sodium carbonate minerals and an application to trona deposition in Lake Magadi (Kenya). Geochimica et Cosmochimica Acta, 1984, 48, pp.571-581. ⟨10.1016/0016-7037(84)90285-0⟩. ⟨hal-00663050⟩
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