High-Pressure Crystal Chemistry and Compressibility of Hydrous Mantle Phases

University Of Louisville Research Foundation Inc, Louisville KY

Investigators

Abstract

Neutron and X-ray diffraction methods will be used to investigate the high- pressure crystal chemistry, hydrogen bonding and compressibility of hydrous phases stable at temperatures and pressures within the upper mantle and transition zone. Experiments will focus on both synthetic and natural systems, including dense hydrous magnesium silicates (wadsleyite, phase E and OH-clinohumite), epidotes, OH-topaz and hydrogarnet. The results of this work will show how structurally incorporated water (hydrogen) affects the behavior of hydrous phases at mantle pressures. Intellectual Merit: Understanding the location and behavior of hydrogen at high pressure of hydrous phases is particularly important because even at very small concentrations hydrogen has such a dramatic affect on both the stability and physical properties of earth materials. At the macroscopic level, the pressure dependence of the volume (equation of state) is used in the calculation of density and thermodynamic parameters, and to extrapolate semi- empirical hydrogen-bonding models to high pressures. Broader Impacts: Mitigation strategies for earthquake hazards are based on geological models developed, in part, from experimental data on the stability and properties of hydrous phases in subducted slabs. Three undergraduates and one graduate student will participate either directly in the experiments, or learn how to analyze crystallographic data and formulate models to interpret measurements. To the extent possible, the results of this work will also be disseminated to students in undergraduate courses designed for both science and non- science majors, and to grades 9-12 students through community outreach programs sponsored by the university. The Ph.D. student funded by this project will be enrolled in an interdisciplinary degree program in chemical physics and geosciences. Interactions of the P.I. and graduate student with the condensed matter and inorganic chemistry will serve to enhance research across scientific disciplines within the university and, possibly, the region.