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

<p>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–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 (500–700 °C). The type IV LPO was found under high shear strain (γ > 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.</p>

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.

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.

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;

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
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