Lattice Vibrations and Spectroscopy of Mantle Phases

Experimental vibrational spectroscopy studies combined with theoretical calculations are used to study and understand the lattice dynamics of minerals under the high-pressure–high-temperature conditions of the Earth's mantle. The results allow us to model and understand the thermodynamic properties, stability fields, and coexistence relations of mantle minerals. Theoretical basis and computational and experimental techniques for obtaining vibrational spectra are described. Applications to major silicates and their transitions that control the Earth's mantle structure are reviewed. Computational and experimental studies have focused on principal lower mantle and transition zone phases that are (Mg,Fe)O magnesiowustite, silicate perovskite, majorite, wadsleyite, ringwoodite, and SiO 2 stishovite. Results for their low-pressure counterparts olivine, pyroxene, and garnet phases that occur mainly within the upper mantle are presented. Lattice dynamics and phase transformations in aluminous and hydrous mineral phases are also described as they play an important role in governing water, radioactive element, and heat production distribution in the Earth's mantle.