Melting experiments on MgSiO3, the major constituent of the Earth's mantle and planetary interiors, have now been conducted at a static pressure of 20 GPa. These experiments reveal the presence of a new garnet-like non-cubic phase of MgSiO3, which melts congruently at 2,250°C. This new silicate phase and its stability have significant implications for mantle mineralogy, chemical fractionation by partial melting and also for the occurrence of aluminium-deficient cubic garnet (majorite) in shocked meteorites. These high-pressure experiments at temperatures 2,000°C have been made possible by the development of a large-volume high-pressure device at Nagoya University1-4.
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