scholarly journals Lattice Preferred Orientation and Deformation Microstructures of Glaucophane and Epidote in Experimentally Deformed Epidote Blueschist at High Pressure

Minerals ◽  
2020 ◽  
Vol 10 (9) ◽  
pp. 803
Author(s):  
Yong Park ◽  
Sejin Jung ◽  
Haemyeong Jung
Keyword(s):  
High Pressure ◽  
Shear Strain ◽  
Shear Plane ◽  
Preferred Orientation ◽  
Shear Direction ◽  
High Shear ◽  
Lattice Preferred Orientation ◽  
Subducting Slab ◽  
Zone Deformation ◽  
Low Shear

To understand the lattice preferred orientation (LPO) and deformation microstructures at the top of a subducting slab in a warm subduction zone, deformation experiments of epidote blueschist were conducted in simple shear under high pressure (0.9–1.5 GPa) and temperature (400–500 °C). At low shear strain (γ ≤ 1), the [001] axes of glaucophane were in subparallel alignment with the shear direction, and the (010) poles were subnormally aligned with the shear plane. At high shear strain (γ > 2), the [001] axes of glaucophane were in subparallel alignment with the shear direction, and the [100] axes were subnormally aligned with the shear plane. At a shear strain between 2< γ <4, the (010) poles of epidote were in subparallel alignment with the shear direction, and the [100] axes were subnormally aligned with the shear plane. At a shear strain where γ > 4, the alignment of the (010) epidote poles had altered from subparallel to subnormal to the shear plane, while the [001] axes were in subparallel alignment with the shear direction. The experimental results indicate that the magnitude of shear strain and rheological contrast between component minerals plays an important role in the formation of LPOs for glaucophane and epidote.

New lattice preferred orientation(LPO) of amphibole experimentally found in simple shear

2020 ◽  
Author(s):  
Junha Kim ◽  
Haemyeong Jung
Keyword(s):  
Grain Size ◽  
High Pressure ◽  
Shear Strain ◽  
Seismic Anisotropy ◽  
Preferred Orientation ◽  
Shear Direction ◽  
High Shear ◽  
Type Iv ◽  
Lower Shear ◽  
Lattice Preferred Orientation

&lt;p&gt;The lattice preferred orientation(LPO) of amphibole has a large effect on seismic anisotropy in the crust. Previous studies have reported four LPO types (I&amp;#8211;IV) of amphibole, but the genesis of type IV LPO, which is characterized by [100] axes aligned in a girdle subnormal to the shear direction, is unknown. In this study, shear deformation experiments on amphibolite were conducted to find the genesis of type IV LPO at high pressure (0.5 GPa) and temperature (500&amp;#8211;700 &amp;#176;C). The type IV LPO was found under high shear strain (&amp;#947; &gt; 3.0) and the sample exhibited grains in a range of sizes but generally smaller than the grain size of samples with lower shear strain. The seismic anisotropy of type IV LPO is lower than in types I-III. The weak seismic anisotropy of highly deformed amphibole could explain weak seismic anisotropy observed in the middle crust.&lt;/p&gt;

Experimental study on the deformation microstructures and crystallographic preferred orientation of glaucophane and epidote in deformed epidote blueschist at high pressure

2021 ◽  
Author(s):  
Yong Park ◽  
Sejin Jung ◽  
Haemyeong Jung
Keyword(s):  
High Pressure ◽  
Shear Strain ◽  
Shear Plane ◽  
Preferred Orientation ◽  
Dislocation Creep ◽  
Shear Direction ◽  
Shear Strain Rate ◽  
High Shear ◽  
Crystallographic Preferred Orientation ◽  
Ebsd Technique

&lt;p&gt;To understand the crystallographic preferred orientation (CPO) of glaucophane and epidote and deformation microstructures at the top of a subducting slab in a warm subduction zone, deformation experiments of epidote blueschist were conducted in simple shear by using a modified Griggs apparatus. Deformation experiments were performed under high pressure (0.9&amp;#8211;1.5 GPa), temperature (400&amp;#8211;500 &amp;#176;C), shear strain (&amp;#947;) in the range of 0.4&amp;#8211;4.5, and shear strain rate of 1.5&amp;#215;10&lt;sup&gt;-5&lt;/sup&gt;&amp;#8211;1.8&amp;#215;10&lt;sup&gt;-4&lt;/sup&gt; s&lt;sup&gt;-1&lt;/sup&gt;. After experiments, CPO of minerals were determined by electron back-scattered diffraction (EBSD) technique, and microstructures of deformed minerals were observed by transmission electron microscopy (TEM). At low shear strain (&amp;#947; &amp;#8804; 1), the [001] axes of glaucophane were in subparallel alignment to shear direction, and the (010) poles were sub-normally aligned to the shear plane. At high shear strain (&amp;#947; &gt; 2), the [001] axes of glaucophane were in subparallel alignment to shear direction, and the [100] axes were sub-normally aligned to the shear plane. At a shear strain between 2 &lt; &amp;#947; &lt; 4, the (010) poles of epidote were in subparallel alignment to shear direction, and the [100] axes were sub-normally aligned to the shear plane. At a high shear strain where &amp;#947; &gt; 4, the alignment of the (010) epidote poles had altered from subparallel to subnormal to the shear plane, while the [001] axes were in subparallel alignment to the shear direction. TEM observations and EBSD mapping revealed that the CPO of glaucophane was developed by dislocation creep, somewhat affected by the cataclastic flow at high shear strain. On the other hand, the CPO development of epidote is considered to have been affected by dislocation creep under a shear strain of 2 &lt; &amp;#947; &lt; 4 but is highly affected by cataclastic flow with rigid body rotation under a high shear strain (&amp;#947; &gt; 4). Our experimental results indicate that the magnitude of shear strain and rheological contrast between component minerals plays an important role on the formation of CPOs of glaucophane and epidote.&lt;/p&gt;

scholarly journals Strain-Induced Fabric Transition of Chlorite and Implications for Seismic Anisotropy in Subduction Zones

Minerals ◽  
2020 ◽  
Vol 10 (6) ◽  
pp. 503
Author(s):  
Dohyun Kim ◽  
Haemyeong Jung ◽  
Jungjin Lee
Keyword(s):  
Shear Strain ◽  
Subduction Zones ◽  
Seismic Anisotropy ◽  
Shear Plane ◽  
Shear Direction ◽  
S Wave ◽  
Lattice Preferred Orientation ◽  
Back Arc

Seismic anisotropy of S-wave, trench-parallel or trench-normal polarization direction of fast S-wave, has been observed in the fore-arc and back-arc regions of subduction zones. Lattice preferred orientation (LPO) of elastically anisotropic chlorite has been suggested as one of the major causes of seismic anisotropy in subduction zones. However, there are two different LPOs of chlorite reported based on the previous studies of natural chlorite peridotites, which can produce different expression of seismic anisotropy. The mechanism for causing the two different LPOs of chlorite is not known. Therefore, we conducted deformation experiments of chlorite peridotite under high pressure–temperature conditions (P = 0.5–2.5 GPa, T = 540–720 °C). We found that two different chlorite LPOs were developed depending on the magnitude of shear strain. The type-1 chlorite LPO is characterized by the [001] axes aligned subnormal to the shear plane, and the type-2 chlorite LPO is characterized by a girdle distribution of the [001] axes subnormal to the shear direction. The type-1 chlorite LPO developed under low shear strain (γ ≤ 3.1 ± 0.3), producing trench-parallel seismic anisotropy. The type-2 chlorite LPO developed under high shear strain (γ ≥ 5.1 ± 1.5), producing trench-normal seismic anisotropy. The anisotropy of S-wave velocity (AVs) of chlorite was very strong up to AVs = 48.7% so that anomalous seismic anisotropy in subduction zones can be influenced by the chlorite LPOs.

scholarly journals Crystallographic preferred orientations of ice deformed in direct-shear experiments at low temperatures

2018 ◽  
Author(s):  
Chao Qi ◽  
David J. Prior ◽  
Lisa Craw ◽  
Sheng Fan ◽  
Maria-Gema Llorens ◽  
...  
Keyword(s):  
Shear Strain ◽  
Electron Backscatter Diffraction ◽  
Numerical Models ◽  
Boundary Migration ◽  
Shear Plane ◽  
Equivalent Strain ◽  
Lattice Rotation ◽  
Dislocation Creep ◽  
Shear Direction ◽  
Primary Cluster

Abstract. We sheared synthetic polycrystalline ice at temperatures of −5, −20 and −30 °C, to different shear strains, up to γ = 2.6 (equivalent strain of 1.5). Cryo-electron backscatter diffraction (EBSD) shows that basal intra-crystalline slip planes become preferentially oriented parallel to the shear plane, in all experiments. This is visualized as a primary cluster of crystal c-axes (the c-axis is perpendicular to the basal plane) perpendicular to the shear plane. In all except the two highest-strain experiments at −30 °C, a secondary cluster of c-axes is observed, at an angle to the primary cluster. With increasing strain, the primary c-axis cluster strengthens. With increasing temperature, both clusters strengthen. In the −5 °C experiments, the angle between the two clusters reduces with increasing strain. The c-axis clusters are elongated perpendicular to the shear direction. This elongation increases with increasing shear strain and with decreasing temperature. Highly curved grain boundaries are more prevalent in samples sheared at higher temperatures. At each temperature, the proportion of and irregularity of curved boundaries decreases with increasing shear strain. Subgrains are observed in all samples. Recrystallized grains and subgrains are similar in size and are both smaller than the original grains. Microstructural interpretations and comparisons of the data from experimentally sheared samples with numerical models suggest that the observed crystallographic orientation patterns result from a balance of the rates of lattice rotation (during dislocation creep) and growth of grains by strain-induced grain boundary migration (GBM). GBM is faster at higher temperatures and becomes less important as shear strain increases. These observations and interpretations provide a hypothesis to be tested in further experiments and using numerical models, with the ultimate goal of aiding the interpretation of crystallographic preferred orientations in naturally deformed ice.

Lattice preferred orientation and stress in polycrystalline hcp-Co plastically deformed under high pressure

2006 ◽  
Vol 100 (2) ◽  
pp. 023510 ◽  
Author(s):  
Sébastien Merkel ◽  
Nobuyoshi Miyajima ◽  
Daniele Antonangeli ◽  
Guillaume Fiquet ◽  
Takehiko Yagi
Keyword(s):  
High Pressure ◽  
Preferred Orientation ◽  
Lattice Preferred Orientation

Lattice preferred orientation of talc and implications for seismic anisotropy

2020 ◽  
Author(s):  
Jungjin Lee ◽  
Haemyeong Jung ◽  
Reiner Klemd ◽  
Matthew Tarling ◽  
Dmitry Konopelko
Keyword(s):  
High Pressure ◽  
Subduction Zones ◽  
Seismic Anisotropy ◽  
Preferred Orientation ◽  
Azimuthal Anisotropy ◽  
Hydrous Minerals ◽  
Ultra High Pressure ◽  
Lattice Preferred Orientation ◽  
Radial Anisotropy ◽  
First Time

&lt;p&gt;Strong seismic anisotropy is generally observed in subduction zones. Lattice preferred orientation (LPO) of olivine and elastically anisotropic hydrous minerals has been considered to be an important factor causing anomalous seismic anisotropy. For the first time, we report on measured LPOs of polycrystalline talc. The study comprises subduction-related ultra-high-pressure metamorphic schists from the Makbal Complex in Kyrgyzstan-Kazakhstan and amphibolite-facies metasomatic schists from the Valla Field Block in Unst, Scotland. The here studied talc revealed a strong alignment of [001] axes (sub)normal to the foliation and a girdle distribution of [100] axes and (010) poles (sub)parallel to the foliation. The LPOs of polycrystalline talc produced a significant P&amp;#8211;wave anisotropy (AVp = 72%) and a high S&amp;#8211;wave anisotropy (AVs = 24%). The results imply that the LPO of talc influence both the strong trench-parallel azimuthal anisotropy and positive/negative radial anisotropy of P&amp;#8211;waves, and the trench-parallel seismic anisotropy of S&amp;#8211;waves in subduction zones.&lt;/p&gt;

Design of Sinusoidal Auxetic Structures for High Shear Flexure

2010 ◽  
Author(s):  
Prabhu Shankar ◽  
Jaehyung Ju ◽  
Joshua D. Summers ◽  
John C. Ziegert
Keyword(s):  
Cell Wall ◽  
Shear Modulus ◽  
Shear Strain ◽  
Analytical Model ◽  
Wall Thickness ◽  
Cell Wall Thickness ◽  
High Shear ◽  
Plane Shear ◽  
Wide Range ◽  
Low Shear

This paper presents the analytical model to predict the effective in-plane shear modulus G12* for auxetic honeycomb mesostructure with sinusoidal re-entrant wall. Also, a comparative study is conducted on the ability of the sinusoidal mesostructure over auxetic mesostructure for high shear flexure. In an effort to design components with high shear flexure, the re-entrant wall of the auxetic honeycomb is replaced with a sinusoidal wall. Existing analytical models that predict the effective in-plane elastic properties for auxetic honeycomb mesostructure are limited to straight re-entrant wall. In order to predict the effective in plane shear modulus, G12*, for conceptual design study, an analytical model is needed. The principle of energy methods is used to determine the effective in-plane shear modulus and is verified with the solution in ABAQUS. The analytical model is in agreement with the computational model with a 10% maximum error over a wide range of cell wall thickness and shear strain. The two structures are designed to possess the same equivalent shear modulus and the degree of shear flexure is measured computationally in terms of yield shear strain. The sinusoidal structure introduces nonlinearity with increase in cell wall thickness and shear strain. This nonlinearity causes the sinusoidal auxetic mesostructure to have low shear flexure at a high shear modulus which is higher than about 10MPa. However, it is marginally better than auxetic mesostructure at a low shear modulus which is 10MPa and less.

scholarly journals Crystallographic preferred orientations of ice deformed in direct-shear experiments at low temperatures

2019 ◽  
Vol 13 (1) ◽  
pp. 351-371 ◽  
Author(s):  
Chao Qi ◽  
David J. Prior ◽  
Lisa Craw ◽  
Sheng Fan ◽  
Maria-Gema Llorens ◽  
...  
Keyword(s):  
Shear Strain ◽  
Electron Backscatter Diffraction ◽  
Numerical Models ◽  
Boundary Migration ◽  
Shear Plane ◽  
Line Length ◽  
Lattice Rotation ◽  
Dislocation Creep ◽  
Shear Direction ◽  
Primary Cluster

Abstract. Synthetic polycrystalline ice was sheared at temperatures of −5, −20 and −30 ∘C, to different shear strains, up to γ=2.6, equivalent to a maximum stretch of 2.94 (final line length is 2.94 times the original length). Cryo-electron backscatter diffraction (EBSD) analysis shows that basal intracrystalline slip planes become preferentially oriented parallel to the shear plane in all experiments, with a primary cluster of crystal c axes (the c axis is perpendicular to the basal plane) perpendicular to the shear plane. In all except the two highest-strain experiments at −30 ∘C, a secondary cluster of c axes is observed, at an angle to the primary cluster. With increasing strain, the primary c-axis cluster strengthens. With increasing temperature, both clusters strengthen. In the −5 ∘C experiments, the angle between the two clusters reduces with strain. The c-axis clusters are elongated perpendicular to the shear direction. This elongation increases with increasing shear strain and with decreasing temperature. Highly curved grain boundaries are more prevalent in samples sheared at higher temperatures. At each temperature, the proportion of curved boundaries decreases with increasing shear strain. Subgrains are observed in all samples. Microstructural interpretations and comparisons of the data from experimentally sheared samples with numerical models suggest that the observed crystallographic orientation patterns result from a balance of the rates of lattice rotation (during dislocation creep) and growth of grains by strain-induced grain boundary migration (GBM). GBM is faster at higher temperatures and becomes less important as shear strain increases. These observations and interpretations provide a hypothesis to be tested in further experiments and using numerical models, with the ultimate goal of aiding the interpretation of crystallographic preferred orientations in naturally deformed ice.

Microstructural and textural evolution of calcite deformed to high shear strain by high-pressure torsion

2019 ◽  
Vol 118 ◽  
pp. 32-47 ◽  
Author(s):  
Roman Schuster ◽  
Gerlinde Habler ◽  
Erhard Schafler ◽  
Rainer Abart
Keyword(s):  
High Pressure ◽  
Shear Strain ◽  
High Pressure Torsion ◽  
High Shear ◽  
Textural Evolution
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