Award Date

12-2011

Degree Type

Thesis

Degree Name

Master of Science in Geoscience

Department

Geoscience

First Committee Member

Pamela Burnley, Chair

Second Committee Member

Michael Wells

Third Committee Member

Sean Mulcahy

Graduate Faculty Representative

Andrew Cornelius

Number of Pages

142

Abstract

Olivine is the most common and the weakest mineral in the upper mantle. Thus the strength of olivine controls the rheology of the earth's upper mantle. The rheology of olivine in the upper mantle has important implications for mantle flow, mountain building, and rates of isostatic adjustment. Recent experimental measurements of the flow strength of deformed olivine polycrystals have assumed a homogeneous state of stress. X-ray synchrotron diffraction experiments have implied that this assumption is not always valid. Elastic Plastic Self Consistent (EPSC) modeling offers an approach to estimating the flow strength of olivine that does not assume a homogeneous stress state. However, for EPSC models of olivine to work properly, all single crystal deformation modes must be considered. Kinking is a deformation mechanism that can be incorporated into the EPSC model to potentially improve the accuracy of the model's output relative to lattice plane diffraction measurements. For this purpose, the geometry of kink bands from deformed Mg2GeO4 olivine polycrystals is characterized using Electron Backscatter Diffraction (EBSD). A range of kink angles is observed from 19º to 68º. The slip system associated with the kink bands in the Mg2GeO4 grains is (100) [001].

Keywords

Dislocations in crystals; Earth — Mantle; Earth sciences; Germanate; Kink; Microstructure; Plasticity; Rheology; Rock deformation; Olivine

Disciplines

Geochemistry | Geology | Mineral Physics

Language

English


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