Shear deformation of nano- and micro-crystalline olivine at seismic slip rates

Thieme, Manuel; Pozzi, Giacomo; Demouchy, Sylvie; Paola, N. De; Barou, Fabrice; Koizumi, Sanae; Bowen, Leon

doi:10.1016/j.tecto.2021.228736

Cited by 3 publications

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References 120 publications

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“…Dislocation microstructures produced in laboratory deformation experiments have been used for comparisons with those produced in nature in order to help determine whether the same rate-controlling creep mechanisms also operate in natural environments [6]. Recently, a growing number of controlled deformation studies have been carried out on olivine using an apparatus known as the deformation DIA (D-DIA) [11][12][13][14][15][16]. There were some studies with the D-DIA that showed the transition from (010)[100] and (001)[100] slip systems (hereafter referred to as a-slip) at low pressures to (010)[001] and (100)[001] slip systems (hereafter referred to as c-slip) at high pressures [17][18][19][20][21][22].…”

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confidence: 99%

A TEM Study on a Polycrystalline Olivine Sample Deformed in a D-DIA under Mantle Conditions

2022

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We carried out an electron microscopy study on a polycrystalline olivine sample that was deformed with multiple deformation cycles under controlled differential stresses and strain rates at high pressures and high temperatures. Low-angle backscattered electron images thereof showed randomly oriented grains. Most of the grains were about 10–20 μm wide. The grains were irregular with wavy grain boundaries, indicating high grain boundary mobility during deformation. Transmission electron microscopy (TEM) images showed complex dislocation microstructure characteristics of high temperature, high pressure, and high strain. Free dislocations were predominantly either short and straight screw dislocations or curved dislocations with mixed screw and edge characters. Many of them split into partial dislocations. The differential stress estimated with the free dislocations was ~780 MPa, which was close to the value of differential stress attained in the final deformation cycle. We also observed dense dislocation tangles, which formed dislocation cell substructures under high strain. The existence of dislocation loops and jogs indicated significant climbing activity, providing evidence for high-temperature creep as the dominant deformation mechanism. All of the dislocations observed in this study were exclusively with a [001] Burgers vector. Dislocations with a [100] Burgers vector were absent, suggesting that the activity of the a-slip (i.e., (010)[100] and (001)[100] slip systems) was completely suppressed. These observations support a conclusion that was reported based on an X-ray texture analysis, which considered that a high pressure promotes the activities of the c-slip (i.e., (010)[001] and (100)[001] slip systems). It appears that the transition from the a-slip to the c-slip was complete with multiple deformation cycles at a relatively lower pressure of 5.1 GPa than previously thought, corresponding to a depth of 165 km in the mantle.

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