Deformation microstructures of olivine and pyroxene in mantle xenoliths in Shanwang, eastern China, near the convergent plate margin, and implications for seismic anisotropy

Park, Yong; Jung, Haemyeong

doi:10.1080/00206814.2014.928240

Cited by 29 publications

(19 citation statements)

References 148 publications

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“…4 ; see Methods Summary for J-index explanations and reference). These values are similar to B-type fabrics observed in most 16 20 21 24 , but not all 17 experiments, and in several natural peridotites 25 26 27 28 29 . Although, we note that some natural peridotites record strong olivine B-type fabrics 30 31 32 33 34 , these are no more common than weaker peridotite B-type fabrics 25 26 27 28 29 .…”

Section: Discussionsupporting

confidence: 85%

Earth's oldest mantle fabrics indicate Eoarchaean subduction

et al. 2016

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The extension of subduction processes into the Eoarchaean era (4.0–3.6 Ga) is controversial. The oldest reported terrestrial olivine, from two dunite lenses within the ∼3,720 Ma Isua supracrustal belt in Greenland, record a shape-preferred orientation of olivine crystals defining a weak foliation and a well-defined lattice-preferred orientation (LPO). [001] parallel to the maximum finite elongation direction and (010) perpendicular to the foliation plane define a B-type LPO. In the modern Earth such fabrics are associated with deformation of mantle rocks in the hanging wall of subduction systems; an interpretation supported by experiments. Here we show that the presence of B-type fabrics in the studied Isua dunites is consistent with a mantle origin and a supra-subduction mantle wedge setting, the latter supported by compositional data from nearby mafic rocks. Our results provide independent microstructural data consistent with the operation of Eoarchaean subduction and indicate that microstructural analyses of ancient ultramafic rocks provide a valuable record of Archaean geodynamics.

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Section: Discussionsupporting

confidence: 85%

Earth's oldest mantle fabrics indicate Eoarchaean subduction

et al. 2016

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“…Skemer et al (2006) found the B-type olivine LPO in garnet peridotites from Cima di Gagnone, Switzerland. Michibayashi et al (2007) and Park and Jung (2015) found B-type olivine LPOs in the southern Mariana trench and in mantle xenoliths from Shanwang, eastern China, respectively. Webber et al (2008) found the B-type olivine LPO in mantle peridotites from Red Hills, New Zealand.…”

Section: Introductionmentioning

confidence: 98%

Deformation microstructures of olivine and chlorite in chlorite peridotites from Almklovdalen in the Western Gneiss Region, southwest Norway, and implications for seismic anisotropy

Kim

Jung

2014

International Geology Review

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Chlorite peridotites from Almklovdalen in southwest Norway were studied to understand the deformation processes and seismic anisotropy in the upper mantle. The lattice preferred orientation (LPO) of olivine and chlorite was determined using electron backscattered diffraction (EBSD)/scanning electron microscopy. A sample with abundant garnet showed [100] axes of olivine aligned sub-parallel to lineation, and [010] axes aligned subnormal to foliation: A-type LPO. Samples rich in chlorite showed different olivine LPOs. Two samples showed [001] axes aligned sub-parallel to lineation, and [010] axes aligned subnormal to foliation: B-type LPO. Two other samples showed [100] axes aligned sub-parallel to lineation, and [001] axes aligned subnormal to foliation: E-type LPO. Chlorite showed a strong LPO characterized by [001] axes aligned subnormal to foliation with a weak girdle subnormal to lineation. Fourier transform infrared (FTIR) spectroscopy of the specimens revealed that the olivines with A-type LPO contain a small amount (170 ppm H/Si) of water. In contrast, the olivines with B-type LPOs contain a large amount (340 ppm H/Si) of water.The seismic anisotropy of the olivine and chlorite was calculated. Olivine showed Vp anisotropy of up to 3.8% and a maximum Vs anisotropy of up to 2.7%. However, the chlorite showed a much stronger Vp anisotropy, up to 21.1%, and a maximum Vs anisotropy of up to 31.7%. A sample with a mixture of 25% of olivine and 75% of chlorite can produce a Vp anisotropy of 14.2% and a maximum Vs anisotropy of 22.9%. Because chlorite has a wide stability field at high pressure and high temperature in the subduction zone, the strong LPO of chlorite can be a source of the observed trench-normal or trench-parallel seismic anisotropy in the mantle wedge as well as in subducting slabs depending on the dipping angle of slab in a subduction zone where chlorite is stable.

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“…The CPO of each mineral, which is induced by differential stress and ductile deformation, depends on the prevailing deformation mechanism (e.g., dislocation slip system); the magnitude, geometry, and history of strain (e.g., coaxial or noncoaxial strain); and the conditions during deformation (e.g., temperature, pressure, differential stress, and fluid content) [e.g., Hansen et al , ; Miyazaki et al , ; Raterron et al , ]. As a consequence, the seismic properties of naturally deformed rocks consisting dominantly of trigonal (e.g., α‐quartz and calcite), hexagonal (e.g., β‐quartz) [ Mainprice and Casey , ; Naus‐Thijssen et al , ; Ward et al , ; Zhao et al , ], orthorhombic (e.g., olivine and orthopyroxene [ Ji et al , , ; Jung et al , ; Lee and Jung , ; Park and Jung , ; Saruwatari et al , ]), monoclinic (e.g., amphibolite and clinopyroxene [ Barberini et al , ; Barruol and Mainprice , ; Ji et al , , ; Ko and Jung , ; Tatham et al , ]), and triclinic (e.g., plagioclase [ Ji and Mainprice , ; Ji and Salisbury , ; Ji et al , ; Satsukawa et al , ]) minerals are often of complex geometry.…”

Section: Introductionmentioning

confidence: 99%

Magnitude and symmetry of seismic anisotropy in mica‐ and amphibole‐bearing metamorphic rocks and implications for tectonic interpretation of seismic data from the southeast Tibetan Plateau

et al. 2015

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We calibrated the magnitude and symmetry of seismic anisotropy for 132 mica‐ or amphibole‐bearing metamorphic rocks to constrain their departures from transverse isotropy (TI) which is usually assumed in the interpretation of seismic data. The average bulk Vp anisotropy at 600 MPa for the chlorite schists, mica schists, phyllites, sillimanite‐mica schists, and amphibole schists examined is 12.0%, 12.8%, 12.8%, 17.0%, and 12.9%, respectively. Most of the schists show Vp anisotropy in the foliation plane which averages 2.4% for phyllites, 3.3% for mica schists, 4.1% for chlorite schists, 6.8% for sillimanite‐mica schists, and 5.2% for amphibole schists. This departure from TI is due to the presence of amphibole, sillimanite, and quartz. Amphibole and sillimanite develop strong crystallographic preferred orientations with the fast c axes parallel to the lineation, forming orthorhombic anisotropy with Vp(X) > Vp(Y) > Vp(Z). Effects of quartz are complicated, depending on its volume fraction and prevailing slip system. Most of the mica‐ or amphibole‐bearing schists and mylonites are approximately transversely isotropic in terms of S wave velocities and splitting although their P wave properties may display orthorhombic symmetry. The results provide insight for the interpretation of seismic data from the southeast Tibetan Plateau. The N‐S to NW‐SE polarized crustal anisotropy in the Sibumasu and Indochina blocks is caused by subvertically foliated mica‐ and amphibole‐bearing rocks deformed by predominantly compressional folding and subordinate strike‐slip shear. These blocks have been rotated clockwise 70–90° around the east Himalayan Syntaxis, without finite eastward or southeastward extrusion, in responding to progressive indentation of India into Asia.

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Deformation microstructures of olivine and pyroxene in mantle xenoliths in Shanwang, eastern China, near the convergent plate margin, and implications for seismic anisotropy

Cited by 29 publications

References 148 publications

Earth's oldest mantle fabrics indicate Eoarchaean subduction

Earth's oldest mantle fabrics indicate Eoarchaean subduction

Deformation microstructures of olivine and chlorite in chlorite peridotites from Almklovdalen in the Western Gneiss Region, southwest Norway, and implications for seismic anisotropy

Magnitude and symmetry of seismic anisotropy in mica‐ and amphibole‐bearing metamorphic rocks and implications for tectonic interpretation of seismic data from the southeast Tibetan Plateau

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