The temperature dependence of the elasticity of Fe-bearing wadsleyite

Data are presented on the elastic properties of β-(Mg0.92Fe0.08)2SiO4 (iron-bearing wadsleyite) from 295 K to 640 K at ambient pressure. Elasticity measurements were made on hot-pressed polycrystals using resonant ultrasound spectroscopy (RUS). Multiple temperature excursions were done with data retrieved during both heating and cooling cycles. Room temperature (RT) values for the adiabatic bulk (KS) and shear (G) moduli are 170.8(1.2) GPa and 108.9(0.4) GPa, respectively. The average derivatives over the temperature (T) range studied are (∂KS/∂T)P = −1.75(0.07) × 10−2 GPa K−1 and (∂G/∂T)P = −1.55(0.06) × 10−2 GPa K−1. Comparison of these results with those from our recent study of Mg-endmember wadsleyite shows no measurable difference in the average (∂KS/∂T)P or (∂G/∂T)P from RT to 640 K due to Fe content. Slight nonlinearity in the temperature dependences of both KS and G are observed, such that second order fits for both KS(T) and G(T) are statistically justified. Whereas, the current nonlinearity in G(T) for β-(Mg0.92Fe0.08)2SiO4 is similar to that observed for β-Mg2SiO4, second order effects in KS(T) were not observed previously for wadsleyite.