Seafloor Geology of the Basement Serpentinite Body in the Ohmachi Seamount (Izu-Bonin Arc) as Exhumed Parts of a Subduction Zone Within the Philippine Sea

Ueda, Hayato; Niida, Kiyoaki; Usuki, Tadashi; Hirauchi, Ken-ich; Meschede, Martin; Miura, Ryuichi; Ogawa, Yujiro; Yuasa, Motohiro; Sakamoto, Izumi; Chiba, Tae; Izumino, Takahiro; Kuramoto, Yoshiyuki; Azuma, Toyoto; Takeshita, Toru; Imayama, Takeshi; Miyajima, Yuki; Saito, Takahiro

doi:10.1007/978-90-481-8885-7_5

Cited by 8 publications

(3 citation statements)

References 36 publications

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“…The remnant arcs on the subducting Philippine Sea plate might be associated with major faults cross-cutting the lithosphere. Ueda et al [2011] described development of 5 km thick serpentinite underlying the Paleogene volcaniclastics of the Izu-Bonin-Mariana arc. They related the serpentinite structure to a large fracture zone (SofuganTectonic Line) or the N-S extension of remnant arcs in the Philippine Sea plate.…”

Section: Subduction Fluid Transport Beneath South Kyushumentioning

confidence: 99%

Shear wave anisotropy beneath the volcanic front in South Kyushu area, Japan: Development of C‐type olivine CPO under H₂O‐rich conditions

2013

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[1] Shear wave splitting from local intermediate-depth earthquakes is investigated to detect the anisotropic structure in the mantle wedge beneath the South Kyushu area, Japan. We observed shear wave splitting with NEE-SWW to NWW-SEE polarization directions and delay times of 0.04-0.63 s. Trench-normal shear wave polarization anisotropy with a delay time greater than 0.3 s probably overlaps in the high V P /V S region at a depth of 100-150 km beneath the volcanic front. Model calculations for the cause of the anisotropy suggest that the development of "C-type" olivine crystallographic preferred orientation (CPO) with a trench-parallel b axis concentration and a trench-normal a axis concentration best reproduces observations compared to A-, B-, or E-type olivine CPOs and antigorite CPO. We conclude that a thick anisotropic layer, approximately 50 km, is formed by concentration of interstitial fluid in peridotite. We briefly discuss the mechanism carrying water to the deep mantle wedge. A possible explanation is that interstitial fluids in the mantle wedge are effectively released because of a decrease in dihedral angles of olivine-fluid interfaces at 150 km depth. Our results imply a close relation between the high density of explosive volcanoes in the South Kyushu area and the underlying water-rich mantle.

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Section: Subduction Fluid Transport Beneath South Kyushumentioning

confidence: 99%

Shear wave anisotropy beneath the volcanic front in South Kyushu area, Japan: Development of C‐type olivine CPO under H₂O‐rich conditions

2013

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“…The seamount consists of high-pressure metamorphic rocks entrained in serpentinite diapirs close to the Palaeogene volcanic front (Ueda et al 2004(Ueda et al , 2011. One serpentinite body is tens of kilometres in diameter (of mostly wehrlite and dunite origin, now largely serpentinized into antigorite schist), which is associated with garnet-hornblende schist with eclogitic facies relics (Ueda et al 2004(Ueda et al , 2011.…”

Section: High-pressure Rock Exhumation Model: Comparison To Japanese mentioning

confidence: 99%

“…This strongly supports some shearing during diapiric intrusion of blueschist-bearing mélanges that were further intruded into turbidite beds of the trench accretionary prism body as discussed above. (2003), where it is applied to occurrences of serpentinite encasing high-pressure blocks of Ueda et al (2004Ueda et al ( , 2011 in the Izu forearc.…”

Section: High-pressure Rock Exhumation Model: Comparison To Japanese mentioning

confidence: 99%

New interpretation of the Franciscan mélange at San Simeon coast, California: tectonic intrusion into an accretionary prism

Ogawa

Mori

Tsunogae

et al. 2014

International Geology Review

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Many concepts and interpretations on the formation of the Franciscan mélange have been proposed on the basis of exposures at San Simeon, California. In this paper, we show the distribution of chaotic rocks, their internal structures and textures, and the interrelationship between the chaotic rocks and the surrounding sandstones (turbidites). Mélange components, particularly blueschists, oceanic rocks, including greenstone, pillow lava, bedded chert, limestone, sandstone, and conglomerate, have all been brecciated by retrograde deformation. The Cambria Slab, long interpreted as a trench slope basin, is also strongly deformed by fluidization, brecciation, isoclinal folding, and thrusting, leading us to a new interpretation that turbiditic rocks (including the Cambria Slab) represent trench deposits rather than slope basin sediments. These rocks form an accretionary prism above mélanges that were diapirically emplaced into these rocks first along sinistralthrust faults, and then along dextral-normal faults. Riedel shear systems are observed in several orders of scale in both stages. Although the exhumation of the blueschist blocks is still controversial, the common extensional fractures and brecciation in most of the blocks in the mélanges and further mixture of various lithologies into one block with mélange muddy matrix indicate that once deeply buried blocks were exhumed from considerable depths to the accretionary prism body, before being diapirically intruded with their host mélange along thrust and normal faults, during which retrograde deformation occurred together with retrograde metamorphism. Recent similar examples of high-pressure rock exhumation have been documented along the Sofugan Tectonic Line in the Izu forearc areas, in the Mineoka belt in the Boso Peninsula, and as part of accretionary prism development in the Nankai and Sagami troughs of Japan. These modern analogues provide actively forming examples of the lithological and deformational features that characterize the Franciscan mélange processes.

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High-pressure, Low-temperature Metamorphism

Ueda¹

2016

Encyclopedia of Marine Geosciences

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Seafloor Geology of the Basement Serpentinite Body in the Ohmachi Seamount (Izu-Bonin Arc) as Exhumed Parts of a Subduction Zone Within the Philippine Sea

Cited by 8 publications

References 36 publications

Shear wave anisotropy beneath the volcanic front in South Kyushu area, Japan: Development of C‐type olivine CPO under H₂O‐rich conditions

Shear wave anisotropy beneath the volcanic front in South Kyushu area, Japan: Development of C‐type olivine CPO under H₂O‐rich conditions

New interpretation of the Franciscan mélange at San Simeon coast, California: tectonic intrusion into an accretionary prism

High-pressure, Low-temperature Metamorphism

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Seafloor Geology of the Basement Serpentinite Body in the Ohmachi Seamount (Izu-Bonin Arc) as Exhumed Parts of a Subduction Zone Within the Philippine Sea

Cited by 8 publications

References 36 publications

Shear wave anisotropy beneath the volcanic front in South Kyushu area, Japan: Development of C‐type olivine CPO under H2O‐rich conditions

Shear wave anisotropy beneath the volcanic front in South Kyushu area, Japan: Development of C‐type olivine CPO under H2O‐rich conditions

New interpretation of the Franciscan mélange at San Simeon coast, California: tectonic intrusion into an accretionary prism

High-pressure, Low-temperature Metamorphism

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Product

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Shear wave anisotropy beneath the volcanic front in South Kyushu area, Japan: Development of C‐type olivine CPO under H₂O‐rich conditions

Shear wave anisotropy beneath the volcanic front in South Kyushu area, Japan: Development of C‐type olivine CPO under H₂O‐rich conditions