Reaction boundary between akimotoite and ringwoodite + stishovite in MgSiO3

The phase boundary between akimotoite and ringwoodite + stishovite in MgSiO 3 was determined using a multi-anvil high-pressure apparatus and synchrotron X-ray radiation. The phase relation was determined by observing the recovered samples using an electron microprobe analyzer. Experimental pressures were monitored by the in situ powdered X-ray diffraction data of gold, which was put in the sample chamber. The reaction boundary between akimotoite and ringwoodite + stishovite was found to occur at P (GPa) = 22.0–0.0012 × T (K). The pressure dependence of the slope of the reaction boundary, d P /d T , determined in our study was smaller than that determined by Gasparik (J Geophys Res 95:15751–15769, 1990). The triple point of ringwoodite + stishovite–wadsleyite + stishovite–akimotoite estimated in our study was at ~20 GPa and ~1700 K.