Laboratory investigation of mechanisms for phase mixing in olivine + ferropericlase aggregates
| Autor: | Mark E. Zimmerman, H. Wiesman, David L. Kohlstedt |
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| Rok vydání: | 2018 |
| Předmět: |
Olivine
Materials science 010504 meteorology & atmospheric sciences Zener pinning General Mathematics General Engineering General Physics and Astronomy Thermodynamics engineering.material 010502 geochemistry & geophysics 01 natural sciences Grain size engineering Grain boundary Shear zone Ferropericlase Strengthening mechanisms of materials 0105 earth and related environmental sciences Grain Boundary Sliding |
| Zdroj: | Philosophical transactions. Series A, Mathematical, physical, and engineering sciences. 376(2132) |
| ISSN: | 1471-2962 |
| Popis: | To investigate the role of grain boundary pinning and the mechanisms by which phase mixing occurs during deformation of polymineralic rocks, we conducted high-strain torsion experiments on samples consisting of olivine plus 30 vol% ferropericlase. Experiments were performed in a gas-medium deformation apparatus at 1524 K and 300 MPa. Samples were deformed to outer radius shear strains of up toγ(R) = 14.1. The value of the stress exponent and the small grain sizes of our samples indicate that our two-phase material deformed by dislocation-accommodated grain boundary sliding. In samples deformed to 1 γ γ ≈ 14, a well-distributed mixture of small ferropericlase grains among the olivine grains developed. Microstructures exhibit similarities to both mechanical and chemical models proposed to describe the processes leading to phase mixing. Our results provide evidence for grain size reduction during phase mixing that results in a grain size significantly smaller than the value predicted by the single-phase recrystallization piezometer for olivine. Thus, phase mixing provides a mechanism for the persistent weakening of rocks that is important for developing and maintaining shear zones necessary for plate tectonics.This article is part of a discussion meeting issue ‘Earth dynamics and the development of plate tectonics'. |
| Databáze: | OpenAIRE |
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