Dynamic Properties of Earth Materials

California Institute Of Technology, Pasadena CA

Investigators

Abstract

Ahrens EAR-0207934 This award will fund a range of studies of the equations of state, sound velocity, thermochemical properties, and thermal conductivity of important model earth materials in the system MgO-SiO2 under conditions accessible only by shock loading of targets that are porous, pre-heated, or specially synthesized dense starting phases. The investigators' multianvil method allows routine preparation of polycrystalline samples of mantle minerals of a size and shape suitable for high-quality shock compression studies. Experiments with majorite, ilmentite, wadsleyite, ringwoodite, and perovskite starting materials and completion of studies on MgSiO3 glass and gem quality enstatite, will yield data at multiple internal energy states, from which the Gruneisen parameter will be extracted under lower mantle conditions. This award will also fund construction of an optical line-imaging VISAR (Velocity Interferometer System For Any Reflector) that will allow measurement of longitudinal and bulk sound velocities under high shock pressure by the overtaking method. This method allows comparison of mineral sound velocities with the Earth itself as well as determination of melting temperatures at ultra-high pressure. Experiments on both porous and preheated MgO will determine its melting behavior above the range previously studied with diamond cell anvils, resolving the enormous discrepancy between theoretical high pressure melting models for MgO and present data to 40 GPa.