Influence of Temperature on the Stability and Kinetic Behavior of the Magnesian Calcites

Abstract

Calcites of varying magnesium contents play a role in processes involving biomineralization, carbonate diagenesis, seawater saturation state, and atmospheric CO₂ sinks. Experimental data using the free-drift dissolution method over a range of controlled temperatures and a pCO2 trf 10-2.5 atm indicate that calcite solubility minima occur at increase-ad MgCO₃ contents as temperature increases; magnesian calcites of 1 to 15 mole % .. MgCO3 are less soluble than calcite between 43 and 54 ° C. The forward dissolution 1:ate of these phases resembles that of magnesite far from equilibrium, but as saturation with a carbonate is approached, calcite kinetics dominates. The solubility and kinetic properties of the magnesian calcites as a function of temperature are used to discuss the role O2 these minerals in sediment and seawater processes.