In-situ elasticity measurement for the unquenchable high-pressure clinopyroxene phase: Implication for the upper mantle

[1] Polycrystal elasticity of the unquenchable MgSiO3 high- pressure clinoenstatite has been measured using ultrasonic interferometry in conjunction with in- situ X- ray diffraction and imaging techniques within its stability field in a large volume multi- anvil apparatus for the first time. At 6.5 GPa, we obtained partial derivativeK(S)/partial derivativeP = 5.6( 3), partial derivativeG/partial derivativeP = 1.5( 1), partial derivativeK(S)/partial derivativeT = - 0.017( 1) GPa K-1 and (partial derivativeG/partial derivativeT) = - 0.015( 1) GPa K-1. Our results show that the elastic velocities of HP- CEN are not only higher than those of OEN but also higher than olivine at upper mantle conditions. According to these new data, the elastic velocities for the " depleted'' mantle composition, with similar to 20 vol% of HP- CEN, would result in similar to 0.8% and similar to 1.6% in difference for P and S waves, respectively, when OEN data were used in previous calculations. Newly measured results also suggest that it is possible to distinguish " undepleted'' and " depleted'' composition models in the upper mantle.