Decomposition boundary from high-pressure clinoenstatite to wadsleyite + stishovite in MgSiO3

The reaction boundary between high-pressure clinoenstatite and wadsleyite + stishovite in MgSiO 3 was investigated using a multi-anvil high-pressure apparatus and synchrotron X-ray diffraction. Experimental pressures were monitored via in situ powdered X-ray diffraction of gold, which was also put into the sample chamber. Stable phases at each pressure and temperature were confirmed by powdered X-ray diffraction data and observing the recovered samples. The reaction boundary was found to occur at P (GPa) = 16.1 + 0.0064 × ( T – 1250) (K), where the pressure dependence of the slope of the reaction boundary, d P /d T , is similar to that of the phase boundary between wadsleyite and ringwoodite. Thus, the stability field of wadsleyite and stishovite expands to a low-temperature region, reconciling an inconsistency recorded between previous studies regarding the phase relation in MgSiO 3 .