In situ measurements of the majorite‐akimotoite‐perovskite phase transition boundaries in MgSiO3

Abstract

Here we report the phase boundaries between majorite, akimotoite (ilmenite), and perovskite in MgSiO3 determined by in situ measurements in a multi‐anvil apparatus. We used both gold and platinum as internal pressure standards at high pressure and temperature. Our results obtained at 1400‐2000°C, together with previous results obtained at 1000‐1200°C by Ono et al. [2001], precisely locate the akimotoite‐perovskite transition boundary at P (GPa) = 25.09 ‐ 0.0027 × T (°C), based on the P‐V‐T equation of state of gold [Anderson et al., 1989]. Our new experimental data show the position of triple point to be 20.0 GPa and 1920°C. The present measurements reconfirm our earlier study [Hirose et al., 2001] that Anderson's gold pressure scale gives slightly higher pressures than the platinum pressure scale proposed either by Jamieson et al. [1982] or Holmes et al. [1989].