Effects of tectonism and magmatism on crack structure in oceanic crust: A seismic anisotropy study

Geology ◽  
2004 ◽  
Vol 32 (1) ◽  
pp. 25 ◽  
Author(s):  
C.H. Tong ◽  
R.S. White ◽  
M.R. Warner ◽  
Keyword(s):  
Oceanic Crust ◽  
Seismic Anisotropy

Seismic Anisotropy in the Lower Oceanic Crust

Nature ◽  
1972 ◽  
Vol 237 (5356) ◽  
pp. 450-451 ◽  
Author(s):  
N. I. CHRISTENSEN
Keyword(s):  
Oceanic Crust ◽  
Seismic Anisotropy ◽  
Lower Oceanic Crust

Twin induced attenuation of seismic anisotropy in lawsonite blueschist

2021 ◽  
Author(s):  
Seungsoon Choi ◽  
Olivier Fabbri ◽  
Gültekin Topuz ◽  
Aral Okay ◽  
Haemyeong Jung
Keyword(s):  
Electron Microscope ◽  
Oceanic Crust ◽  
Subduction Zones ◽  
Seismic Anisotropy ◽  
Elastic Anisotropy ◽  
S Wave ◽  
Electron Backscattered Diffraction ◽  
Crystal Preferred Orientation ◽  
Fabric Strength ◽  
Scanning Electron

<p>Lawsonite is an important mineral to understand seismic anisotropy in subducting oceanic crust because of its large elastic anisotropy and prevalence in cold subduction zones. However, there is a lack of knowledge on how lawsonite twinning affects seismic anisotropy despite previous reports showing the existence of twins in lawsonite. We thus investigated the effect of twins in lawsonite on crystal preferred orientation (CPO), fabric strength, and seismic anisotropy of lawsonite using the lawsonite blueschists from Alpine Corsica (France) and Sivrihisar Massif (Turkey). CPOs of minerals were measured by using the electron backscattered diffraction (EBSD) facility attached to scanning electron microscope. The EBSD analyses of lawsonite revealed that {110} twin in lawsonite is developed and [001] axes are strongly aligned subnormal to the foliation and both [100] and [010] axes are aligned subparallel to the foliation. It is found that the existence of twins in lawsonite could induce a large attenuation of seismic anisotropy, especially for the maximum S-wave anisotropy up to 18.4 % in lawsonite and 24.3 % in the whole rocks. Therefore, lawsonite twinning needs to be considered in the interpretation of seismic anisotropy in the subducting oceanic crust in cold subduction zones.</p>

scholarly journals Twin Induced Reduction of Seismic Anisotropy in Lawsonite Blueschist

Minerals ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 399
Author(s):  
Seungsoon Choi ◽  
Olivier Fabbri ◽  
Gültekin Topuz ◽  
Aral I. Okay ◽  
Haemyeong Jung
Keyword(s):  
Oceanic Crust ◽  
Subduction Zones ◽  
Seismic Anisotropy ◽  
Elastic Anisotropy ◽  
Electron Backscatter Diffraction ◽  
S Wave ◽  
Crystal Preferred Orientation ◽  
Electron Backscatter ◽  
Backscatter Diffraction ◽  
Insufficient Knowledge

Lawsonite is an important mineral for understanding seismic anisotropy in subducting oceanic crust due to its large elastic anisotropy and prevalence in cold subduction zones. However, there is insufficient knowledge of how lawsonite twinning affects seismic anisotropy, despite previous studies demonstrating the presence of twins in lawsonite. This study investigated the effect of lawsonite twinning on the crystal preferred orientation (CPO), CPO strength, and seismic anisotropy using lawsonite blueschists from Alpine Corsica (France) and the Sivrihisar Massif (Turkey). The CPOs of the minerals are measured with an electron backscatter diffraction instrument attached to a scanning electron microscope. The electron backscatter diffraction analyses of lawsonite reveal that the {110} twin in lawsonite is developed, the [001] axes are strongly aligned subnormal to the foliation, and both the [100] and [010] axes are aligned subparallel to the foliation. It is concluded that the existence of twins in lawsonite could induce substantial seismic anisotropy reduction, particularly for the maximum S-wave anisotropy in lawsonite and whole rocks by up to 3.67% and 1.46%, respectively. Lawsonite twinning needs to be considered when determining seismic anisotropy in the subducting oceanic crust in cold subduction zones.

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