Subduction-stage pressure-temperature path of eclogite from the Sambagawa belt: Prophetic record for oceanic-ridge subduction

Aoya, Mutsuki; Uehara, Shigeo; Matsumoto, Masatoshi; Wallis, Simon; Enami, Masaki

doi:10.1130/g19927.1

Cited by 73 publications

(78 citation statements)

References 13 publications

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“…The boundary between the Kula and Pacific plates was a ridge which was subducted underneath SW Japan and is observed in an oceanic stratigraphic sequence in the Shimanto accretionary complex (Taira et al 1988). This suggests that the exhumation of the Sanbagawa high-pressure schists was triggered by the ridge subduction (Maruyama, 1997;Itaya, Hyodo & Fukui, 1993;Aoya et al 2003). The oblique ridge subduction underneath palaeo-SW Japan as a convergent margin was suggested for the along-arc variation in age of the Ryoke granitic rocks by Nakajima, Shirahase & Shibata (1990) and Kinoshita (1995).…”

Section: Discussionmentioning

confidence: 92%

Age (K–Ar phengite)–temperature–structure relations: a case study from the Ishigaki high-pressure schist belt, southern Ryukyu Arc, Japan

Nuong

Itaya

Nishimura³

2008

Geol. Mag.

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The Ishigaki high-pressure schist belt in the southern Ryukyu Arc is correlated with the Suo high-pressure schist belt in southwest Japan. The former metamorphic sequence is composed mainly of basic and pelitic schists and is subdivided into three zones, the lower-grade zone A, the medium-grade zone B and the high-grade zone C, based on the mineral assemblages of the basic schists. The K-Ar phengite age gives 188-205 Ma for zone A, 196-206 Ma for zone B and 208-220 Ma for zone C, while the apparent d 002 spacing of carbonaceous materials is 3.590-3.437 Å , 3.415-3.390 Å and 3.387-3.364 Å , respectively. The age-d 002 relationships suggest that the ages become older with increasing metamorphic temperature. This positive age-temperature relationship in the Ishigaki area contrasts with a negative relationship in the Nishiki area in the Suo belt. The two areas also display a contrasting thermal structure with the former area having an inverted metamorphic gradient and the latter displaying a normal thermal structure. These contrasting age-temperaturestructure relationships in the metamorphic belt could be due to different tectonic styles relating to the exhumation of the metamorphic sequences. We suggest that the ages obtained are related directly to the ductile deformation history of the matrix phengite below the closure temperature (500 • C) during exhumation of the host rocks. The duration from the beginning of exhumation to the apparent resetting of the phengite K-Ar system was different between the two metamorphic sequences, and significantly longer in the Ishigaki than the Nishiki.

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Section: Discussionmentioning

confidence: 92%

Age (K–Ar phengite)–temperature–structure relations: a case study from the Ishigaki high-pressure schist belt, southern Ryukyu Arc, Japan

Nuong

Itaya

Nishimura³

2008

Geol. Mag.

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“…The mid-ocean ridge between the Kula and Pacific plates was subducted beneath SW Japan as recorded in the ocean plate stratigraphy (Matsuda and Isozaki, 1991) of the Shimanto AC (Taira et al, 1988). This suggests that the exhumation of the HP schists was triggered off by the ridge subduction (Maruyama et al, 1996;Aoya et al, 2003;Aoki et al, 2008). Although all the boundaries between the two neighboring oceanic plates among these five oceanic plates have not yet been documented as mid-oceanic ridges, the exhumation of the Suo, Sanbagawa sensu stricto and Shimanto HP belts in SW Japan could be correlated with subduction events of the plate boundaries between the Farallon and Izanagi plates, Izanagi and Kula plates and Kura and Pacific plates, respectively, as predicted by Isozaki and Maruyama (1991) and Aoki et al (2011, this issue).…”

Section: Evolution Of Sanbagawa Belt (Sensu Stricto)mentioning

confidence: 98%

Evolution of the Sanbagawa and Shimanto high-pressure belts in SW Japan: Insights from K–Ar (Ar–Ar) geochronology

Itaya

Tsujimori

Liou

2011

Journal of Asian Earth Sciences

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“…The belt is dominated by metasediments and metabasalt that were originally part of a subducting oceanic slab. These rocks record metamorphism in the greenschist, epidote-amphibolite, and eclogite facies (Enami et al, 1994;Aoya, 2003), involving the subduction of a young, warm slab (Aoya, 2003). Schists of the Sanbagawa belt contain a prominent east-west-striking subhorizontal stretching lineation developed during exhumation in response to extension parallel to the paleotrench axis (Wallis, 1998).…”

Section: Geological Setting and Vein Occurrencementioning

confidence: 99%

Velocity of vertical fluid ascent within vein-forming fractures

Okamoto

Tsuchiya

2009

Geology

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Quartz-albite-calcite veins in metamorphic rocks of the Sanbagawa belt, Japan, contain sugary mosaics of equant quartz grains <0.01-1.6 mm in size (blocky texture). The quartz crystals show euhed ral to subhedral double-terminated crystal shape, and concentric growth zoning, indicating suspension in aqueous fl uid during crystal growth until formation of a framework within the crack. Such a crystallization process is only possible when downward crystal settling is balanced by upward fl uid fl ow. Application of crystal settling theory to the crystal size distributions within the veins reveals an extremely high rate of fl uid ascent during blocky vein formation (10 -2 to 10 -1 m/s) due to the low viscosity of the hydrothermal fl uid (~10 -4 Pa⋅s). Such a high rate of ascent suggests the injection of fl uids from mobile hydrofractures within deeper levels of the subduction zone.

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Subduction-stage pressure-temperature path of eclogite from the Sambagawa belt: Prophetic record for oceanic-ridge subduction

Cited by 73 publications

References 13 publications

Age (K–Ar phengite)–temperature–structure relations: a case study from the Ishigaki high-pressure schist belt, southern Ryukyu Arc, Japan

Age (K–Ar phengite)–temperature–structure relations: a case study from the Ishigaki high-pressure schist belt, southern Ryukyu Arc, Japan

Evolution of the Sanbagawa and Shimanto high-pressure belts in SW Japan: Insights from K–Ar (Ar–Ar) geochronology

Velocity of vertical fluid ascent within vein-forming fractures

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