Phase transformations of pure Mg2SiO4 into a spinel structure under high pressures and temperatures

Abstract

A double-stage split-sphere apparatus has been developed for a series of phase-transformation studies at high pressures up to about 300 kb and at high tempepatures of around 1000°C. First, the coesite-stishovite transition curve has been determined to calibrate the pressures at high temperatures. Then the olivine-distorted spinel transition in pure Mg2SiO4 has been investigated in the temperature range from 700 to 1200°C and at pressures above 100kb. The spinel phase of pure Mg2SiO4 has been finally synthesized at 1000°C at pressures higher than 220kb. Mg-rich spinels in the system Fe2SiO4-Mg2SiO4 have also been synthesized in order to complete the phase diagram at 1000°C. © 1972, The Seismological Society of Japan, The Volcanological Society of Japan, The Geodetic Society of Japan. All rights reserved.