Role of Al2O3, Fe2O3, and CaO in the Earth's Lower Mantle

高压实验为我们提供了地幔矿物学的基础知识。虽然许多地幔矿物学模型是通过比较相对简单的系统(如MgO-FeO-SiO_2系统)的高压实验结果与观测的地震数据而建立的，但详细的模型需要准确测量地幔矿物的物理性质和与地幔成分相关的系统中的相平衡数据，包括Al_2O_3、Fe_2O_3和CaO。这项提议的目的是了解Al_2O_3、Fe_2O_3和CaO在地球下地幔中的作用。具体地说，本研究的目的是(1)确定在下地幔条件下形成的天然玄武岩组成中的富Al相和富Al-Ca相的晶体结构；(2)了解Al3+和Fe3+取代在(Mg，Fe)SiO_3-钙钛矿结构中的作用；(3)确定Al3+和Fe3+取代对(Mg，Fe)SiO_3-钙钛矿状态方程的影响。这一建议的结果将被用来确定在较低地幔压力下俯冲玄武岩地壳的密度，从而了解俯冲玄武岩地壳在地幔中的命运和相关的地幔动力学。这些结果将为进一步了解含Al~(3+)和Fe~(3+)的(Mg，Fe)SiO_3钙钛矿的晶体化学和下地幔化学提供依据

9873577FeiHigh-pressure experiments have provided us with basic knowledge of mantle mineralogy. While many mineralogical models of the mantle have been developed by comparing the high-pressure experimental results in relatively simplified systems, such as the system MgO-FeO-SiO2, with the observed seismic data, detailed models require accurately measured physical properties of mantle minerals and phase equilibrium data in systems relevant to mantle compositions including components such as Al2O3, Fe2O3, and CaO. The aim of this proposal is to understand the role of Al2O3, Fe2O3, and CaO in the Earth's lower mantle. Specifically, this research is designed (1) to determine the crystal structures of Al- and Al-Ca-rich phases formed in natural basaltic composition under lower mantle conditions, (2) to understand the role of Al3+ and Fe3+ substitutions in the (Mg,Fe)SiO3-perovskite structure, and (3) to determine the effect of Al3+ and Fe3+ substitutions on equations-of-state of (Mg,Fe)SiO3-perovskite. The results from this proposal will be used to determine the density of subducted basaltic crust at lower mantle pressures and therefore to understand the fate of the subducted basaltic crust in the mantle and associated mantle dynamics. The results will provide further understanding of the crystal chemistry of Al3+ and Fe3+-bearing (Mg,Fe)SiO3-perovskites and the chemistry of the lower mantle