Effects of brine chemistry and polymorphism on clumped isotopes revealed by laboratory precipitation of mono- and multiphase calcium carbonates

Overall, clumped isotope values of CaCO3 minerals precipitated between 23 °C and 91 °C (with and without NaCl addition) follow a line with a slope close to results from statistical thermodynamics. We conclude for calcium carbonate and hydromagnesite that the combined effect of salt ion concentration, acid fractionation and polymorphism is negligible for Cl− and Na+ with respect to clumped isotope geochemistry, but that offsets are possible in brines containing high concentrations of CaCl2.