View article

Elastic wave velocities of ringwoodite with compositions of Mg₂SiO₄, (Mg_0.8Fe_0.2)₂SiO₄ and (Mg_0.5Fe_0.5)₂SiO₄ have been measured to address the effect of iron on the elastic properties of silicate spinel under high pressure. Ultrasonic measurements on specimens produced by hot-pressing at about 19GPa and at 1200°C were conducted at pressures up to 14GPa at room temperature in a multianvil apparatus. Pressure was estimated from a relationship between the travel time in an Al₂O₃ buffer rod and the pressure estimated from in situ X-ray diffraction measurements. Thus, measured bulk modulus (K) of ringwoodite slightly increases with increasing iron content, while the pressure derivative of the bulk modulus remains virtually the same (K′=4.4 for X_Fe=Fe/(Fe+Mg)=0–0.5). In contrast, the shear modulus (G) decreases significantly with increasing iron content, while the pressure derivative of the shear …