Boron isotope fractionation during adsorption on aragonite and calcite in artificial seawater and NaCl aqueous solutions

Adsorption of dissolved species on mineral surfaces is a key elementary process, which controls crystal growth and incorporation of trace elements into mineral structures, affecting the isotopic composition of geological archives. Changes of chemical composition of aqueous solution can induce significant variations in the type,
concentration and isotopic composition of boron surface species incorporated by CaCO$_3$. To better understand and quantify these effects, the boron isotope fractionation associated with B adsorption on calcite and aragonite was investigated in artificial seawater and equimolar solutions of NaCl (0.5 M) at room temperature and 7.5 ≤ pHNBS ≤ 11.9. Boron adsorption on aragonite was 2–4 times stronger than on calcite, in agreement with the higher affinity of aragonite for borate ions reported by previous studies.