Stability and breakdown of Ca 13 CO 3 melt associated with formation of 13 C-diamond in static high pressure experiments up to 43GPa and 3900K

Melting of calcium carbonate Ca13CO3, stability of the melt and its decomposition were studied in static high pressure experiments at pressures of 11–43GPa and temperatures of 1600–3900K using diamond anvil cell technique with laser heating. We observed formation of 13C-graphite (below 16GPa) and 13C-diamond (between 16 and 43GPa) on decomposition of the Ca13CO3 melt at temperatures above 3400K. At temperatures below 3400K congruent melting of calcium carbonate was confirmed. The experimental results were applied to construction of the phase diagram of CaCO3 up to 43GPa and 3900K focusing at the melting curve of calcium carbonate and the decomposition phase boundary of CaCO3 melt.