Mineral precipitation rates during the complete evaporation of the Merouane Chott ephemeral lake

The Merouane Chott, located in southeastern Algeria, is an ideal natural system for studying mineral dissolution and precipitation rates because it (1) undergoes annual cycles of filling and complete evaporation, and (2) has a simple, well defined hydrology. The major element concentrations of Merouane Chott lake waters were measured weekly from January to June 2003. These concentrations are used together with estimates of the Chott lake volume and infiltration rates to calculate the temporal evolution of the total mass of these major elements. Element precipitation rates are generated by dividing the first derivative of total mass of each element with respect to time by the Chott surface area. Mass balance considerations yield precipitation rate estimates for halite, calcite, and gypsum during the complete evaporation of the lake. These rates are compared with the saturation indexes of these minerals to deduce the degree to which they are consistent with laboratory measured rates available in the literature.