HR: 10:35h
AN: V42A-02 INVITED     [Abstracts]
TI: The Influence of Oxygen Environment on Kinetic Properties of Minerals
AU: Kohlstedt, D L
EM: dlkohl@umn.edu
AF: University of Minnesota, 310 Pillsbury Drive SE, Minneapolis, MN 55455 United States
AU: * Hier-Majumder, S
EM: saswata.hier-majumder@yale.edu
AF: Yale University, P.O. Box 208109, New Haven, CT 06520-8109 United States
AB: In this presentation, we review experimental determinations of the influence of oxygen environment on the physical properties of olivine. Kinetic properties of solids such as electrical conductivity and viscosity that are often functions of ionic diffusivity depend on the oxygen fugacity. Ionic diffusivity in solids can be expressed as the product of point defect concentration and point defect diffusivity. While thermogravimetry experiments reveal a pronounced dependence of point defect concentration on oxygen fugacity, electrical conductivity and thermogravimetry point defect relaxation experiments yield the point defect mobility. Results from these two types of experiments on olivine demonstrate that the power law dependence of ionic diffusivity on oxygen fugacity arises from the oxygen fugacity dependence of the point defect concentration alone. We also discuss experimental determination of the influence of oxygen environment on dislocation structures (i.e., deformation mechanisms) of olivine. Results from creep tests on single crystals of olivine indicate that for crystals compressed along a direction $45^{\mathrm{o}}$ to the [100] and [001] crystallographic directions, the deformation mechanism changed from glide or cross slip of screw dislocations to the motion of near-edge dislocations as the oxygen fugacity was increased from $10^{-11}$ to $10^{-3}$ atm.
DE: 3620 Crystal chemistry
DE: 3904 Defects
DE: 3914 Electrical properties
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2004 AGU Fall Meeting