Strength and elasticity of ringwoodite at upper mantle pressures

The differential stress supported by a natural iron-bearing ringwoodite was determined using energy-dispersive synchrotron x-ray diffraction in a radial geometry in a diamond anvil cell. The yield strength of ringwoodite was found to increase nearly linearly from 5.8(5) GPa at a pressure of 6.2 GPa to 10.2(9) GPa at a pressure of 27.0 GPa. When scaled by the shear modulus, silicate yield strengths are systematically higher than metals, oxides, and halides at pressures up to30 GPa. For silicates, the yield strength is 5-7% of the shear modulus in this pressure range, whereas for the other classes of solids the yield strength is typically less than 2% of the shear modulus. The results show that ringwoodite has a small postive elastic anisotropy over this pressure range.