Dynamic Properties of Earth Materials

AhrensEAR-0207934该奖项将资助一系列关于在只有通过冲击加载多孔、预热或特殊合成的致密起始相的目标的条件下才能访问的条件下的状态方程、声速、热化学性质和热导率的研究。研究人员的多顶锤方法允许常规制备适合高质量冲击压缩研究的大小和形状适合的地幔矿物多晶样品。以镁铝榴石、硅灰石、斜方辉石、环形辉石和钙钛矿为原料进行的实验，以及对镁硅玻璃和宝石性质顽辉岩的研究的完成，将产生多种内能态的数据，从中提取出在下地幔条件下的Gruneisen参数。该合同还将资助建造光学线路成像VISAR(任何反射器的速度干涉仪系统)，该系统将允许通过超车方法测量高冲击压力下的纵向和整体声速。这种方法可以将矿物声速与地球本身进行比较，并确定超高压下的熔融温度。对多孔氧化镁和预热氧化镁进行的实验将确定其熔化行为高于以前用钻石槽顶锤研究的范围，解决了氧化镁高压熔化理论模型与目前数据之间的巨大差异，目前的数据为40 Gpa。

AhrensEAR-0207934This 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.