Chemical composition of a saline lake on Enderbury Island, Phoenix Island Group, Pacific Ocean

Ion activity products for the dissolution of calcite, aragonite, gypsum, monetite, brushite, dolomite, magnesite, hydroxyapatite, and fluorapatite were calculated for a South Pacific guano island brine with an ionic strength of 6.4. Environmental conditions for the brine at the time of analysis and of sampling indicated saturation with respect to calcite, aragonite, gypsum, hydroxyapatite and fluorapatite; a comparison of the ion activity products and equilibrium constants indicated saturation or supersaturation with respect to most minerals found in lake sediments or elsewhere on the island. The results suggest that chemical thermodynamic calculations for brines may have some usefulness despite the many assumptions and estimations that must be made.