Formation of primary kimberlite melts - Constraints from experiments at 6-12Â GPa and variable CO2/H2O

► Near-liquidus phase relations of kimberlites with various CO2 and H2O contents. ► Increasing CO2 activity stabilizes SiO2-rich phases on the liquidus. ► Addition of H2O results in a moderate decease in liquidus temperature and reduction of pyroxene crystallization field. ► Primary kimberlite magmas contain 15-20 wt.% CO2 + H2O at CO2/H2O controlled by source composition.