Development of a Single-Crystal Mineral Elasticity Database and Applications to Crustal and Upper Mantle Mineralogy

The single-crystal elastic stiffness tensor fully characterizes the anisotropic elastic response of minerals. An understanding of how such elastic properties vary with pressure, temperature, structure, and composition are needed to interpret seismic data for the Earth. Additionally, elastic moduli are important for understanding many solid-state phenomena including mechanical stability, interatomic interactions, material strength, compressibility, and phase transition mechanisms. A database of single-crystal elastic properties of minerals and related phases is being assembled. This dataset currently incorporates over 400 sets of elastic constant measurements on more than 270 separate phases. In addition to compiling the individual elastic stiffnesses, the database also allows calculation of a variety of additional properties including anisotropy factors, bulk and linear compressibilities, and stability criteria, as well as evaluation of aggregate properties including bounds and averages of bulk, shear, Young's modulus, Poisson's ratio and elastic wave speeds. Extensions of the database to include high pressure and high temperature data as well as theoretical calculations are being planned. Examples of application of this database to geophysical problems will be highlighted. Specific applications to be discussed include: 1) variation of elastic anisotropy with pressure for mantle and crustal minerals; 2) evaluation of elasticity data for pyroxenes revealing major structural and chemical controls on elasticity as well as remaining ambiguities and uncertainties.