Physical Properties of Core and Deep Mantle Constituents

University Of Washington, Seattle WA

Investigators

Abstract

Brown 0106683 Seismic studies of Earth's solid inner core indicate that the inner core is elastically anisotropic and inhomogeneous, and that the apparent axis of inner core anisotropy may rotate differentially from Earth's mantle. In order to fully interpret these data, information is needed on shear wave propagation through dense, high-pressure metals, particularly iron. For most candidate lower mantle constituents the bulk moduli, as functions of pressure, are reasonably well constrained by experiment; less, however, is known about the behavior of the shear modulus. Efforts to understand both radial and lateral variation of seismic velocities in the lower mantle are limited by the remaining uncertainty in the pressure and temperature dependence of the shear elastic constants. Using the technique of Impulsive Stimulated Scattering, interfacial waves can be generated between the suface of an opaque sample in the high-pressure diamond-anvil cell and the surrounding pressure medium. The velocities of these waves, which are particularly sensitive to the shear elastic constants, are then determined. Specific goals include: (1) determination of full tensorial elastic and thermal properties of iron, iron alloys, and other metals at high pressures and (2) determination of isotropic elastic shear moduli at very high pressure of synthesized, polycrystalline, lower mantle phases.