Petrological constraints on the formation conditions and retrograde <i>P–T</i> path of the Kotsu eclogite unit, central Shikoku

Matsumoto, Masatoshi; Wallis, Simon; Aoya, Mutsuki; Enami, Masaki; Kawano, Jun; Seto, Yusuke; Shimobayashi, Norimasa

doi:10.1046/j.1525-1314.2003.00449.x

Cited by 47 publications

(70 citation statements)

References 26 publications

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“…12). Similar relationship between the mode of occurrence and chemical composition of phengite has been reported from an eclogite in the Kotsu area, eastern Shikoku (Matsumoto et al, 2003). In the Kotsu eclogite phengite grains lying within the schistosity show a distinct chemical zonation with the celadonite rich rim composition close to the composition of the phengite replacing the garnet and a more celadonite poor core.…”

Section: Choice Of Equilibrium Compositionssupporting

confidence: 77%

Peak conditions of kyanite-bearing quartz eclogites in the Sanbagawa metamorphic belt, central Shikoku, Japan

Miyamoto

Enami

Tsuboi

et al. 2007

Journal of Mineralogical and Petrological Sciences

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Kyanite bearing eclogitic assemblages occur in the highest grade zone of the Sanbagawa metamorphic belt, central Shikoku, Japan. The eclogites consist mainly of garnet, omphacite, phengite, kyanite, epidote, quartz and rutile. Compositionally variable amphibole (glaucophane/barroisite/pargasite), phengite and paragonite occur as inclusions in garnet and other eclogite facies phases. Careful examination of garnet zoning in kyanite eclogites suggests that (i) most garnet grains show complex zoning consisting of relatively Ca rich/Mg poor inner and Ca poor/Mg rich outer segments, (ii) the inner segment of the zoned garnet formed at the eclogite facies stage, and (iii) the Mg rich outermost rim of garnet does not always represents a composition at peak eclogite stage but could form at lower pressure conditions of subsequent epidote amphibolite facies. The assemblage of inner segment of garnet, omphacite, phengite, kyanite and quartz points to equilibrium conditions of 2.3 2.4 GPa/675 740 °C. The metamorphic P T conditions of the eclogite facies stage reported in literature have been estimated assuming that the outermost rim of garnet with Mg rich composition was in equilibrium with other eclogite facies phases. Therefore, P T estimations of the eclogite facies stage in the Sanbagawa metamorphic belt should be re examined carefully on the basis of textural and compositional heterogeneities of constituent minerals.

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Section: Choice Of Equilibrium Compositionssupporting

confidence: 77%

Peak conditions of kyanite-bearing quartz eclogites in the Sanbagawa metamorphic belt, central Shikoku, Japan

Miyamoto

Enami

Tsuboi

et al. 2007

Journal of Mineralogical and Petrological Sciences

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“…The peak pressures estimated for the Highashi-akaishi body are consistent with 2.3 -3.7 GPa pressure estimates from an associated 100-m-scale enclave of kyanite-quartz eclogite [Enami, 2003] that lies on the NE margin of the Higashiakaishi body (Figure 1b) but are distinctly higher than those of other members of the Eclogite unit such as the Seba and Kotsu bodies [Aoya, 2001;Matsumoto et al, 2003]. The above petrological information suggests it is necessary to subdivide the Eclogite unit into two or more separate domains with distinct tectonic histories.…”

Section: Geological Settingsupporting

confidence: 74%

“…The presence of paragonite during prograde and retrograde conditions shows that peak pressure in at least some members of the Eclogite unit did not exceed 2.3 GPa [Aoya, 2001, Matsumoto et al, 2003. Detailed structural studies of the eclogite bodies reveal a pre-Ds deformation history distinct from the Besshi unit [Aoya and Wallis, 1999].…”

Section: Geological Settingmentioning

confidence: 94%

Structural and petrological constraints on the tectonic evolution of the garnet‐lherzolite facies Higashi‐akaishi peridotite body, Sanbagawa belt, SW Japan

Mizukami

Wallis

2005

Tectonics

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[1] The Higashi-akaishi peridotite body in the Sanbagawa metamorphic belt is a unique example of a kilometer-scale body including garnet-lherzolite facies rocks from an oceanic subduction-type orogen. In this body, four distinct deformational phases D 1 , D 2 , D 3 , and D 4 can be defined. The tectonic significance of D 1 is unclear. Microstructural observations and application of garnet-orthopyroxene geothermobarometry suggest that D 2 took place during high-temperature subduction up to depths of $100 km (from 2.3 GPa to above 2.8 GPa at temperature of 700-800°C) or more. D 3 represents a major phase of exhumation. After exhumation the Higashi-akaishi body became juxtaposed with the adjacent Besshi and Eclogite units at a depth of around 35 km (1 GPa). The common history of the two units after D 3 is shown by the intertectonic growth of tremolite between D 3 and D 4 that corresponds to a stage of intertectonic growth of plagioclase in the Besshi and Eclogite units. Both the spatial distribution and the estimated pressuretemperature (P-T) conditions of this intertectonic phase of mineral growth in the different units are in excellent agreement. The development of an antigorite schistosity during the late stage of D 2 indicates an anticlockwise P-T path with cooling at depths of around 100 km. The association of the antigorite-bearing fabric and the onset of exhumation after the D 2 stage suggest that the density decrease due to antigorite formation may have been sufficient to trigger the exhumation of dense ultramafic body from UHP conditions in subduction zones. Syn-D 2 water introduction and the anticlockwise P-T path are expected when convection in the mantle wedge brings peridotite toward a subduction boundary through mantle wedge or when peridotite is dragged down along a subduction boundary that is progressively cooling immediately after initiation of subduction. Citation: Mizukami, T., and S. R. Wallis (2005), Structural and petrological constraints on the tectonic evolution of the garnet-lherzolite facies Higashi-akaishi peridotite body, Sanbagawa belt, SW Japan, Tectonics, 24, TC6012,

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“…Abbreviations of rock-body names other than KT (Kotsu) follow Fig.3. Petrologically derived P-T paths (Mizukami & Wallis (2005) for HA, Endo (2010) and Endo et al (2012) for WI, Aoya et al (2003) and Weller et al (2015) for KT, and Enami (1998) for the Shirataki unit are shown by bold arrows, and those derived using thermal model of Endo et al (2012) by dashed bold arrows. (a) 117-109 Ma.…”

Section: Fettes and Desmons 2007mentioning

confidence: 99%

“…Other 3 results of ridge-approach model by Iwamori (2000), which incorporates mantle convection at depths >30 km and uses v = 6.3 cm/year, are shown by dashed bold lines labeled by the corresponding ages of the slab at trench, 2.5, 1.0 and 0 Ma. Katayama et al 2001 540 Ma Okamoto et al 2004-Miyamoto et al, 2007 ; Engebretson 89 Ma Okudaira and Yoshitake, 2004Nakajima et al, 1990;, 1991;Otsuki, 1992;, 1993;Sakaguchi, 1996;Maruyama et al, 1997;Iwamori, 2000;Aoya et al, 2003Wallis et al, 2009Nakajima et al, 2004aNakajima et al, 1990;, 199385-80 Ma Wallis et al, 2009Taira et al, 2016 89 Ma 86 Ma…”

Section: Fettes and Desmons 2007mentioning

confidence: 99%

Recognition of the ‘early’ Sambagawa metamorphism and a schematic cross-section of the Late-Cretaceous Sambagawa subduction zone

Aoya¹,

Endo²

2017

Jour. Geol. Soc. Japan

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Recent petrological studies on the Sambagawa metamorphic belt in Shikoku have recognized that the coarse-grained eclogite-bearing lithologies (so-called tectonic blocks in earlier studies) in the Besshi area exclusively preserve evidence for the early Sambagawa metamorphism, which can be related to onset of the Sambagawa subduction system during Early Cretaceous (c. Ma). Geological mapping and associated multidisciplinary studies on the regional (spatially widespread) Sambagawa metamorphism (both the eclogite-facies and main metamorphisms) have revealed the tectonic framework of the Late-Cretaceous Sambagawa subduction zone as follows: (i) a spreading ridge was approaching close to the trench; (ii) the subducting slab was coupled with the convective mantle at depth of > km; (iii) thickness of the hanging-wall continental crust waskm; and (iv) the forearc mantle wedge ( -km depth) was largely serpentinized. These features allow us to draw a semi-quantitative cross-section of the Sambagawa subduction zone at around -Ma, implying that boundary conditions for thermo-mechanical modeling aiming to simulate exhumation of high-P/T metamorphic rocks are now well constrained. It has also become clear that ultramafic blocks dispersed in the higher-grade part of the Sambagawa belt were derived from the mantle wedge, i.e. the corresponding part of the belt has been re-evaluated as a fossil subduction boundary of a relatively warm subduction zone. Field-based petrological studies in the Sambagawa belt can, therefore, have potential to provide invaluable information on material behaviors at the slab-mantle wedge interface including domains of episodic tremor and slip (ETS) in presentday warm subduction zones.

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Petrological constraints on the formation conditions and retrograde P–T path of the Kotsu eclogite unit, central Shikoku

Cited by 47 publications

References 26 publications

Peak conditions of kyanite-bearing quartz eclogites in the Sanbagawa metamorphic belt, central Shikoku, Japan

Peak conditions of kyanite-bearing quartz eclogites in the Sanbagawa metamorphic belt, central Shikoku, Japan

Structural and petrological constraints on the tectonic evolution of the garnet‐lherzolite facies Higashi‐akaishi peridotite body, Sanbagawa belt, SW Japan

Recognition of the ‘early’ Sambagawa metamorphism and a schematic cross-section of the Late-Cretaceous Sambagawa subduction zone

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