Time-Space Distribution and Petrologic Diversity of Japanese Ophiolites

Ishiwatari, Akira

doi:10.1007/978-94-011-3358-6_37

Cited by 16 publications

(12 citation statements)

References 66 publications

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“…Southwestern Japan is a well‐developed, circum‐Pacific type orogenic belt with oceanward growth of the accretionary complex since the middle Paleozoic (Fig. 1), as determined by a large amount of field‐geological and biostratigraphic data (Hayasaka 1987; Nishimura 1990; Ishiwatari 1991; Isozaki & Itaya 1991; Isozaki 1996; Nakajima 1997). Paleozoic ophiolite and blueschist have been sporadically distributed in the Chugoku Mountains, occupying the highest structural positions in the nappe pile.…”

Section: Geological Settingmentioning

confidence: 99%

Blueschist‐facies metamorphism during Paleozoic orogeny in southwestern Japan: Phengite K–Ar ages of blueschist‐facies tectonic blocks in a serpentinite melange beneath early Paleozoic Oeyama ophiolite

Tsujimori

Itaya

1999

Island Arc

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Blueschist‐bearing Osayama serpentinite melange develops beneath a peridotite body of the Oeyama ophiolite which occupies the highest position structurally in the central Chugoku Mountains. The blueschist‐facies tectonic blocks within the serpentinite melange are divided into the lawsonite–pumpellyite grade, lower epidote grade and higher epidote grade by the mineral assemblages of basic schists. The higher epidote‐grade block is a garnet–glaucophane schist including eclogite‐facies relic minerals and retrogressive lawsonite–pumpellyite‐grade minerals. Gabbroic blocks derived from the Oeyama ophiolite are also enclosed as tectonic blocks in the serpentinite matrix and have experienced a blueschist metamorphism together with the other blueschist blocks. The mineralogic and paragenetic features of the Osayama blueschists are compatible with a hypothesis that they were derived from a coherent blueschist‐facies metamorphic sequence, formed in a subduction zone with a low geothermal gradient (~ 10°C/km). Phengite K–Ar ages of 16 pelitic and one basic schists yield 289–327 Ma and concentrate around 320 Ma regardless of protolith and metamorphic grade, suggesting quick exhumation of the schists at ca 320 Ma. These petrologic and geochronologic features suggest that the Osayama blueschists comprise a low‐grade portion of the Carboniferous Renge metamorphic belt. The Osayama blueschists indicate that the ‘cold’ subduction type (Franciscan type) metamorphism to reach eclogite‐facies and subsequent quick exhumation took place in the northwestern Pacific margin in Carboniferous time, like some other circum‐Pacific orogenic belts (western USA and eastern Australia), where such subduction metamorphism already started as early as the Ordovician.

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Section: Geological Settingmentioning

confidence: 99%

Blueschist‐facies metamorphism during Paleozoic orogeny in southwestern Japan: Phengite K–Ar ages of blueschist‐facies tectonic blocks in a serpentinite melange beneath early Paleozoic Oeyama ophiolite

Tsujimori

Itaya

1999

Island Arc

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“…The WPCB extends along a great circle for more than 25000 km around the Pacific Ocean rim and includes the western Pacific islands (e.g., Japan, Ryukyu islands, Taiwan, Philippines, Indonesia, Papua New Guinea, eastern Australia, and New Zealand) and the Cordilleran belts of western North and South America (Ishiwatari 1991(Ishiwatari , 1994Dilek 2003;Dilek andFurnes 2011, 2014;Furnes et al 2014). The WPCB ophiolites (e.g., Josephine, Trinity, Smartville, Itogon, Papua New Guinea, Zambales, and Yakuno) typically show geochemical and structural characteristics of SSZ or volcanic-arc ophiolites and are found mostly on or among the accreted oceanic and trench sediments of active continental margins (Ishiwatari 1994;Dilek 2003;Dilek and Polat 2008;Dilek andFurnes 2011, 2014).…”

Section: Introductionmentioning

confidence: 99%

Mantle Potential Temperature Estimates of Basalt from the East Taiwan Ophiolite

Shellnutt¹,

Hsieh

2016

Terr. Atmos. Ocean. Sci.

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The East Taiwan Ophiolite (ETO) is a fragment of the eastern-most South China Sea that was accreted to the Eurasian margin during the Pliocene and is a member of the Western Pacific and Cordilleran belt ophiolite group. Ophiolites from the Western Pacific and Cordilleran belt are typically subduction-related (i.e., supra-subduction or volcanic-arc) but the ETO is compositionally, isotopically and mineralogically similar to subduction-unrelated ophiolites. The primary melt compositions of ETO basaltic rocks were calculated and range from high-Mg basalt to picrite (i.e., MgO = 10 to 14 wt%). The mantle potential temperature (T P ) estimates are within the range of ambient mantle (1300 -1400°C) and other mid-ocean ridge ophiolites (i.e., Macquarie Island and Masirah) indicating that it is consistent with a mid-ocean ridge setting. Mantle potential temperature estimates for rocks from a mantle-plume-type ophiolite (i.e., 1620 -1630°C) are anomalously high whereas rocks from supra-subduction zone ophiolites show a wider range that extends from ambient (i.e., Troodos and Semail) T P to very high (i.e., Betts Cove and Bay of Islands) T P .

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“…Ultramafic rocks of the Cumulate Member contain amphibole, but they are present mostly in the interstices of olivine and clinopyroxene or in the reaction zone between olivine and plagioclase. The order of crystallization for the Cumulate Member, which corresponds to the sequence of L‐type ophiolite of Ishiwatari (, ), also indicates the parental magma was MORB‐like. These features imply that the magma was derived from a moderate‐degree of partial melting of a depleted source with suppressed involvement of H 2 O‐rich fluid.…”

Section: Discussionmentioning

confidence: 99%

“…Plagioclase is rarely present in these rocks filling interstitial part of euhedral‐subhedral clinopyroxene and olivine, although it is completely replaced by secondary minerals such as grossular. Crystallization sequence for the Cumulate Member estimated from the modal variation, mineral compositions, and texture is olivine, clinopyroxene, and plagioclase, which corresponds to the sequence of L‐type ophiolite of Ishiwatari (, ).…”

Section: A Review On the Hayachine–miyamori Ophiolite And The Kitakammentioning

confidence: 99%

Evolution processes of Ordovician–Devonian arc system in the South‐Kitakami Massif and its relevance to the Ordovician ophiolite pulse

et al. 2015

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The South Kitakami Massif is one of the oldest geological domains in Japan having Silurian strata with acidic pyroclastic rocks and Ordovician–Silurian granodiorite–tonalite basement, suggesting that it was matured enough to develop acidic volcanisms in the Silurian period. On the northern and western margin of the South Kitakami Massif, an Ordovician arc ophiolite (Hayachine–Miyamori Ophiolite) and high‐pressure and low‐temperature metamorphic rocks (Motai metamorphic rocks) exhumed sometime in the Ordovician–Devonian periods are distributed. Chronological, geological, and petrochemical studies on the Hayachine–Miyamori Ophiolite, Motai metamorphic rocks, and other early Paleozoic geological units of the South Kitakami Massif are reviewed for reconstruction of the South Kitakami arc system during Ordovician to Devonian times with supplementary new data. The reconstruction suggests a change in the convergence polarity from eastward‐ to westward‐dipping subduction sometime before the Late Devonian period. The Hayachine–Miyamori Ophiolite was developed above the eastward‐dipping subduction through three distinctive stages. Two separate stages of overriding plate extension inducing decompressional melting with minor involvement of slab‐derived fluid occurred before and after a stage of melting under strong influence of slab‐derived fluids. The first overriding plate extension took place in the back‐arc side forming a back‐arc basin. The second one took place immediately before the ophiolite exhumation and near the fore‐arc region. We postulate that the second decompressional melting was triggered by slab breakoff, which was preceded by slab rollback inducing trench‐parallel wedge mantle flow and non‐steady fluid and heat transport leaving exceptionally hydrous residual mantle. The formation history of the Hayachine–Miyamori Ophiolite implies that weaker plate coupling may provide preferential conditions for exhumation of very hydrous mantle. Very hydrous peridotites involved in arc magmatism have not yet been discovered except for in the Cambrian–Ordovician periods, suggesting its implications for global geodynamics, such as the thermal state and water circulation in the mantle.

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Time-Space Distribution and Petrologic Diversity of Japanese Ophiolites

Cited by 16 publications

References 66 publications

Blueschist‐facies metamorphism during Paleozoic orogeny in southwestern Japan: Phengite K–Ar ages of blueschist‐facies tectonic blocks in a serpentinite melange beneath early Paleozoic Oeyama ophiolite

Blueschist‐facies metamorphism during Paleozoic orogeny in southwestern Japan: Phengite K–Ar ages of blueschist‐facies tectonic blocks in a serpentinite melange beneath early Paleozoic Oeyama ophiolite

Mantle Potential Temperature Estimates of Basalt from the East Taiwan Ophiolite

Evolution processes of Ordovician–Devonian arc system in the South‐Kitakami Massif and its relevance to the Ordovician ophiolite pulse

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