In situ observation of ilmenite-perovskite phase transition in MgSiO3 using synchrotron radiation

In situ observations of the ilmenite-perovskite transition in MgSiO3 were c arried out in a multianvil high-pressure apparatus interfaced with synchrot ron radiation. The phase boundary between ilmenite and perovskite in the te mperature range of 1300-1600 K was determined to be P (GPa) = 28.4(+/-0.4) - 0.0029(+/-0.0020)T (K) based on Jamieson's equation of state of gold [Jam ieson et at., 1982] and P (GPa) = 27.3(+/-0.4) - 0.0035(+/-0.0024)T (K) bas ed on Anderson's equation of state of gold [Anderson et al., 1989]. The con sistency of our results, using Jamieson's equation of state, with previous studies obtained by quench methods leads us to conclude that the 660 km sei smic discontinuity in the mantle can be attributed a phase transition to pe rovskite phase. However, the phase boundary based on the Anderson's equatio n of state implies that the depth of the 660-km seismic discontinuity does not match the pressure of this transition.