Equation of state and strength of natural majorite

The bulk modulus of a natural sample of cubic majorite, one of the primary components of the Earth's transition zone, has been determined by two independent methods: quasi-hydrostatic compression in the diamond anvil cell and Brillouin spectroscopy at room pressure. The two measurements agree well, and together yield a zero-pressure isothermal bulk modulus KOT = 162.7 (±3.3) GPa, and a pressure derivative KOT = 6.6 (±0.8). Additional compression experiments under nonhydrostatic conditions show that majorite supports shear stresses of at least 2 to 3 GPa at pressures of 7–11 GPa, among the highest values yet documented in silicates or oxides at comparable pressures. These results imply a high strength for majorite, suggesting that the transition zone could be strong to a degree that may influence deformation and heat transfer within the Earth.

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