3:45 PM - 4:00 PM
[SMP38-14] Phase diagram of MgSiO3 in the upper mantle
Keywords:Pyroxene, Upper mantle, Phase diagram
We performed the high-pressure experiments using a multi-anvil high-pressure system combined with a synchrotron radiation source made it possible to acquire precise data from samples under high-pressure and high-temperature conditions. Experimental details have been described elsewhere [1,2]. A synthetic gel was used to produce a reactive and homogeneous starting material. The chemical composition of the synthesized gel was MgSiO3.
The reaction boundaries in MgSiO3 were determined over the range of 1150–1450 K. The stability of each phase was determined by observing the powdered X-ray diffraction data and analyzing the recovered samples. The reaction boundary between high-pressure clinoenstatite and wadsleyite + stishovite was found to occur at P (GPa) = 16.1 + 0.0064 x (T-1250) (K). According to our new data, the stability field of wadsleyite and stishovite expands to a low temperature region. The reaction boundary between ringwoodite + stishovite and akimotoite was found to occur at P (GPa) =22.0 - 0.0012 x T (K) . This indicated that the triple point of ringwoodite+stishovite-wadsleyite+stishovite-akimotoite estimated in our study was at ~20 GPa and ~1700 K. The revised phase boundaries reconcile inconsistencies recorded between previous studies regarding the phase relation in MgSiO3
 S. Ono et al. (2011) Phys. Chem. Minerals, 38, 735-740.
 S. Ono et al. (2013) Phys. Chem. Minerals, 40, 811-816.
 S. Ono et al. (2017) Phys. Chem. Minerals, 44, 425-430.