Melting of San Carlos olivine in the presence of carbon at 6-12 GPa

Experiments at 6-12 GPa showed that San Carlos olivine surrounded by carbon melts incongruently at 1400 C and higher temperatures, producing olivine with lower Fe contents, pyroxene, carbide, and carbonate melt. The relatively low melting temperature of 1400 C, independent of pressure, is consistent with carbonate melting. The new evidence for the reduced stability of olivine at high temperatures in the presence of carbonate melts is consistent with geophysical observations, and results in a substantially improved agreement between the experimentally determined phase relations and the observed seismic velocity structure of the upper mantle.