Mechanisms of equilibrium and kinetic oxygen isotope effects in synthetic aragonite at 25°C

Aragonite was precipitated in the laboratory at 25°C in isotopic equilibrium with Na-Ca-Mg-Cl-CO3 solutions at two different pH values (i.e., pH=∼8.2 and ∼10.8) by the constant addition method. On the basis of the oxygen isotope composition of the aragonite precipitates, it was demonstrated that the equilibrium aragonite–water fractionation factor is independent of the pH of the parent solution and equal to:1000lnα(aragonite–H2O)=29.12±0.09To …