Congruent Melting of Calcium Carbonate in a Static Experiment at 3500 K and 10-22 GPa: Its Role in the Genesis of Ultradeep Diamonds

摘要

Resulting from static experiments performed to study the phase state of CaCO_(3-), it was found that its melting is congruent at 20—22 GPa and 3500 K. The obtained experiment data show that the field of congruent melting of calcium carbonate is rather broad (form 2300 to 3500-3800 K at 20—22 GPa). However, the potential presence of a high-temperature phase boundary at which CaCO_3 is decomposed into CaO and CO_2 is not ruled out. The existence of a wide area of congruent melting of calcium carbonate (a common primary inclusion in diamonds of the transition zone and lower mantle of the Earth) allow one to consider deep-seated melts as potential parental media for ultradeep diamonds.