A theoretical model of component activities in magnesian calcites.

Abstract

Calcium carbonate, calcite, and magnesium carbonate, magnesite, form a series of solid solutions with compositions ranging 0 to 50% magnesite which is dolomite the end member of the series. The calcite magnesite solid solutions are called magnesian calcites (Mg-calcites). Mg-calcites exist in nature, in soils, in marine skeletal materials, in some marine cements, etc., and their existence has been associated with the supersaturation of calcite in sea water and the soil solution of some calcareous soils. They are clearly more soluble than calcite, but their chemical properties has not been defined. This paper examines the basic chemistry of the Mg-calcites and develops a theoretical model derived from the regular solution model and based on classical equilibrium thermodynamics. This model can be used to predict solubility and explain the behavior of the Mg-calcites.