Self-consistent ion-by-ion growth model for kinetic isotopic fractionation during calcite precipitation

Using calcite as a model system, we derive expressions for growth rate and isotopic fractionation as a function of oversaturation and Ca2+:CO32− in solution. Increasing oversaturation increases mineral growth rate and drives isotope partitioning towards the kinetic limit, while increasing the concentration of Ca2+ relative to CO32− at a given oversaturation tends to drive crystal growth towards isotopic equilibrium. These competing effects attenuate the magnitude of isotope fractionations observable in terrestrial environments.