Experimental study of trace element distribution between calcite, fluorite and carbonatitic melt in the system CaCO3 + CaF2 + Na2CO3 ± Ca3(PO4)2 at 100 MPa

Here we present an experimental study of the distribution of a broad range of trace elements between carbonatite melt, calcite and fluorite. The experiments were performed in the CaCO₃ + CaF₂ + Na₂CO₃ ± Ca₃(PO₄)₂ synthetic system at 650-900 °C and 100 MPa using rapid-quench cold-seal pressure vessels. Starting mixtures were composed of reagent-grade oxides, carbonates, Ca₃(PO₄)₂ and CaF₂ doped with 1 wt% REE-HFSE mixture. The results show that the distribution coefficients of all the analyzed trace elements for calcite and fluorite are below 1, with the highest values observed for Sr (0.48-0.8 for calcite and 0.14-0.3 for fluorite) and Y (0.18-0.3). The partition coefficients of REE gradually increase with increasing atomic number from La to Lu. The solubility of Zr, Hf, Nb and Ta in the synthetic F-rich carbonatitic melts, which were used in our experiments, is low and limited by crystallization of baddeleyite and Nb-bearing perovskite. [ABSTRACT FROM AUTHOR]