Sound velocities of wadsleyite beta-(Mg0.88Fe0.12)(2)SiO4 to 10 GPa

We measured the sound velocity of wadsleyite beta-(Mg0.88Fe0.12)(2)SiO4 to 9.6 GPa at room temperature using ultrasonic techniques in a uniaxial split -cylinder apparatus using a polycrystalline specimen hot-pressed at 14 GPa and 1200 degrees C. Bench-top Velocity measurements yielded V-p = 9.33(3) k m/s and V-s = 5.43(2) km/s; the calculated bulk modulus (K) and shear modul us (G) are 172(2) GPa and 106(1) GPa, respectively. These K and G values ar e indistinguishable from those for single crystal and polycrystalline speci mens of Mg2SiO4-wadsleyite. Pressure derivatives of the bulk and shear modu li have been obtained by fitting the current experimental data to 9.6 GPa u sing third-order, finite strains equations, yielding K-S0' = 4.6(1) and G(0 )'= 1.5(1). From comparison with previous data for similar specimens and te chniques, we observe no effect of iron content on the pressure derivatives of either the bulk or shear moduli. within the limited compositional range investigated.