Phosphoric acid fractionation factors for calcite and aragonite between 25 and 75 °C: Revisited

This paper reports the results of an investigation to re-determine the phosphoric acid fractionation factor for calcite and aragonite in order to improve the accuracy and limit the uncertainty of this very important quantity. The 18O/16O ratio of 100% of the oxygen in calcite and aragonite was determined directly by combining data from a two-step procedure involving thermal decomposition of the carbonate, followed by fluorination of the …