Does deviatoric stress increase Al ₂ O ₃ solubility in bridgmanite?

Phase relations in the MgSiO3-Al2O3 system were investigated at 40.0 GPa and 1700K, and at 44.0, 55.7 GPa and an estimated temperature of ∼2300 K using a multi-anvil apparatus combined with in situ X-ray diffraction. At 55.7 GPa and ∼2300 K, coexisting bridgmanite and corundum did not equilibrate. At 44.4 GPa and ∼2300 K, bridgmanite contains 19.1 ± 3.6 mol % of Al2O3, and corundum contains 14.6 ± 1.6 mol % of MgSiO3. At 40.0 GPa and 1700K, bridgmanite contains 24.4 ± 2.3 mol % of Al2O3, which is significantly larger than previously determined, and corundum contains 11.0 ± 1.9 mol % of MgSiO3. We suggest that the increase in Al2O3 solubility in bridgmanite may be related to deviatoric stress, although alternative kinetic or textural explanations cannot be excluded. These results indicate that more detailed studies under stress are required to define element partitioning in minerals at lower mantle conditions.