Rock seismic anisotropy of the low‐velocity zone beneath the volcanic front in the mantle wedge

Michibayashi, K.; Oohara, Tatsuya; Satsukawa, Takako; Ishimaru, Satoko; Arai, Shoji; Okrugin, Victor M.

doi:10.1029/2009gl038527

Cited by 18 publications

(13 citation statements)

References 35 publications

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“…This anisotropy pattern is typical of peridotites which olivine CPO has an orthorhombic or axial [100] symmetry [ Tommasi et al , 2004; Vauchez et al , 2005]. It is also in good agreement with the seismic properties calculated for another Avacha volcano xenolith collection by Michibayashi et al [2009]. Moreover, Vp/Vs 1 and Vp/Vs 2 ratios are minimum for propagation directions at high angle (>30°) to the lineation and the foliation, respectively.…”

Section: Seismic Propertiessupporting

confidence: 81%

Seismic properties of the supra‐subduction mantle: Constraints from peridotite xenoliths from the Avacha volcano, southern Kamchatka

Soustelle

Tommasi

2010

Geophysical Research Letters

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International audienceThis work presents seismic properties derived from a detailed microstructural study of supra-subduction mantle xenoliths extracted by the active Avacha volcano in the southern Kamchatka arc. These peridotites underwent low-stress deformation and syn- to late-kinematic reactive percolation of hydrous melts or fluids leading to local orthopyroxene enrichment and dispersion of the olivine CPO in the shallow mantle wedge. All samples show an axial [ 100] olivine CPO implying fast S-wave polarization parallel to the flow direction in the mantle. Orthopyroxene-enrichment by reactive fluids/melts percolation lowers the Vp/Vs ratio, but cannot explain the Vp/Vs ratios <1.7 mapped in the Japan and Andes forearc mantle. These low Vp/Vs ratios may however be explained by considering the intrinsic anisotropy of the peridotites

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Section: Seismic Propertiessupporting

confidence: 81%

Seismic properties of the supra‐subduction mantle: Constraints from peridotite xenoliths from the Avacha volcano, southern Kamchatka

Soustelle

Tommasi

2010

Geophysical Research Letters

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“…The anisotropy in the mantle wedge results from the LPO of olivine caused by the subduction‐driven back‐arc spreading and mantle convection [ Nicolas and Christensen , 1987; Karato et al , 2008; Wiens et al , 2008]. Based on the stress field and thermal structure of the upper mantle beneath NE Japan, several recent studies suggested that, while deformation throughout most of the mantle wedge is controlled by diffusion creep, the anisotropic zone of dislocation creep is limited to a thin layer with relatively high stress and low temperature located right above the subducting slab and another thin layer right beneath the island arc crust [ Katayama , 2009; Michibayashi et al , 2006, 2009]. Recent P wave anisotropic tomography shows that the anisotropy in the central portion of the mantle wedge is weaker than that in the uppermost mantle and atop the subducting slab [ Wang and Zhao , 2008, 2010; Eberhart‐Phillips and Reyners , 2009; Huang et al , 2011].…”

Section: Anisotropy In the Mantle Wedge And The Slabmentioning

confidence: 99%

Shear wave anisotropy in the crust, mantle wedge, and subducting Pacific slab under northeast Japan

Huang

Zhao

Wang

2011

Geochem. Geophys. Geosyst.

122

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[1] To study the anisotropic structure beneath northeast (NE) Japan, we made 4366 shear wave splitting measurements using high-quality seismograms of many earthquakes occurring in the crust and the subducting Pacific slab. Our results provide important new information on the S wave anisotropy in the upper crust, lower crust, mantle wedge, and subducting Pacific slab. In the upper crust, the anisotropy is mainly caused by the stress-aligned fluid-saturated microcracks. The measured delay times (DTs) increase to 0.10 s at 10-11 km depth; the fast velocity directions (FVDs) are parallel to either the tectonic stress or the strike of active faults. The maximum DTs for the low-frequency earthquakes near the Moho are 0.15-0.17 s, suggesting strong anisotropy at the base of the crust or in the uppermost mantle. The measurements for the intermediate-depth earthquakes in the Pacific slab show dominant E-W (trench-normal) FVDs in the back-arc area and N-S (trench-parallel) FVDs in the fore-arc area. The trench-normal FVDs in the back-arc area are caused by the corner flow in the mantle wedge as a result of the subduction of the Pacific plate. The maximum DTs for the slab earthquakes reach 0.30-0.32 s at 100 km depth, but only half of the total DTs are produced in the mantle wedge. The small DTs in the mantle wedge may result from an isotropic or weak anisotropic zone in the middle of the mantle wedge. In the fore arc, the dominant trench-parallel FVDs for the slab earthquakes are consistent with those for the upper crust earthquakes, and ∼80% of the total DTs can be accounted for by the anisotropy in the crust. In the subducting Pacific slab, the trench-parallel FVDs may reflect either the original fossil anisotropy in the Pacific plate when the plate was produced in the mid-ocean ridge or the preferred orientations of the crystals and cracks in the upper part of the subducting slab.Components: 8500 words, 15 figures.

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“…C-type LPO has been detected in rocks from the deep upper mantle such as those from Alpe Arami in Switzerland (Frese et al 2003), Ugelvik in Norway , Sulu ultra-high pressure terrane in Eastern China (Xu et al 2006;Wang et al 2013), and the North Qaidam ultrahigh pressure belt in northwestern China (Jung et al 2013). In addition, numerous studies have reported the deformation microstructures of olivine derived from subduction zones (Mehl et al 2003;Mizukami et al 2004;Michibayashi et al 2009) and collision zones (Skemer et al 2006;Tommasi et al 2006;Jung 2009;Palasse et al 2012;Michibayashi & Oohara 2013;Jung et al 2014). However, studies of the deformation microstructures of olivine related to mantle metasomatism in continental rift zones have been very limited.…”

Section: Introductionmentioning

confidence: 99%

Petrofabrics of olivine in a rift axis and rift shoulder and their implications for seismic anisotropy beneath the Rio Grande rift

2014

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Mantle-derived xenoliths associated with continental rifting can provide important information about the mantle structure and the physicochemical properties of deformation processes in the upper mantle. Metasomatized spinel peridotites from Adam's Diggings (AD) at a rift shoulder and Elephant Butte (EB) at the rift axis in the Rio Grande rift (RGR) were investigated to understand the deformation processes and seismic anisotropy occurring in the upper mantle. As determined through analysis of the lattice preferred orientation (LPO) of olivine by using a scanning electron microscope equipped with electron backscatter diffraction (SEM/EBSD), AD peridotites exhibited C-type LPO of olivine indicating a dominant slip system of (100)[001] at the rift shoulder, whereas EB peridotites exhibited A-type LPO indicating a dominant slip system of (010)[100] at the rift axis. Both geochemical data and microstructural observations indicate that the localized mantle enrichment processes, including melts with hydrous fluids, controlled multiple mantle metasomatisms and deformation of rocks under wet conditions (with olivine C-type LPO) at the rift shoulder (AD), whereas mantle depletion by decompression partial melting caused deformation of rocks under dry conditions (with olivine A-type LPO) at the rift axis (EB). These observations provide evidence for localized hydration and physicochemical heterogeneity of the upper mantle in the RGR zone. Seismic anisotropy observed beneath this zone can be attributed to the transtensional rupture, such as inhomogeneous stretching, and the petrofabrics of olivine beneath the study area.

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Rock seismic anisotropy of the low‐velocity zone beneath the volcanic front in the mantle wedge

Cited by 18 publications

References 35 publications

Seismic properties of the supra‐subduction mantle: Constraints from peridotite xenoliths from the Avacha volcano, southern Kamchatka

Seismic properties of the supra‐subduction mantle: Constraints from peridotite xenoliths from the Avacha volcano, southern Kamchatka

Shear wave anisotropy in the crust, mantle wedge, and subducting Pacific slab under northeast Japan

Petrofabrics of olivine in a rift axis and rift shoulder and their implications for seismic anisotropy beneath the Rio Grande rift

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