We investigate the melting behaviour of carbonates in the system CaCO3-MgCO3 at 6 and 9 GPa and high temperature in the Multi-Anvil press. We use the rocking mode of the press to determine the phase relations during melting of carbonates at the Mg-rich side of the system CaCO3-MgCO3 in the absence and in the presence of H2O. Previous studies report tremendous quenching problems as primary grown carbonates could not be distinguished from the quenched melt. We equilibrate the system at 6 GPa and T over six hours by continuously rocking the whole press and let the carbonates swim and grow in the melt. However, shortly before quenching the temperature we stopp the rotation and thus could separate the crystals from the melt as they sank down. Compared to the results of static experiments the corresponding phase diagram is significantly different.
Fig.: BSE picture of a cross-section of the recovered capsule (Pt- white color in the picture) with sample (inside) of the experiment MA490 showing the spinifex texture of the melt in the middle and the dark magnesite crystals (first solids) on the right and on the left.