Intermediate high-pressure exhumation of the northern segment of the Sanbagawa belt, Saruta-gawa area, central Shikoku, Japan

Banno, Yasuyuki

doi:10.1016/s0024-4937(99)00060-2

Cited by 23 publications

(20 citation statements)

References 25 publications

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“…Therefore, there is a significant temperature gap between The above-mentioned amphibole-zoning pattern is similar to the report by Banno (2000), who found it in the albite-biotite zone, equivalent to the epidote-amphibolite (EA) facies, in the Saruta-gawa area. Banno (2000) concludes that the observed amphibole zoning pattern reflects the decompression with a significant cooling path during the early stage of the exhumation. However, our finding of Brs-bearing metabasite is in the lower-grade part of the Sanbagawa belt.…”

Section: Discussionsupporting

confidence: 86%

“…In the case of the Sanbagawa belt, Brs and hornblende in metabasites of the garnet and albite-biotite zones in the Asemi-gawa and Dozan-gawa areas are commonly rimmed by Wnc and/or Act (e.g., Otsuki and Banno, 1990;Okamoto and Toriumi, 2004), and these compositional changes in amphibole interpreted to have formed by isothermal decompression at an early stage of exhumation (Okamoto and Toriumi, 2004). On the other hand, amphibole grains with a Brs core, a Na-amp mantle and a Wnc and/or Act rim are reported from the albite-biotite zone in the Saruta-gawa area by Banno (2000), who interpreted this zoning pattern as in terms of decompression associated with significant cooling at an early stage of exhumation. Those findings clearly suggest that the exhumation path of San-bagawa metamorphic rocks in central Shikoku is not uniform.…”

Section: Introductionmentioning

confidence: 99%

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Petrology and possible significance of barroisite–bearing metabasite from the Kebara Formation in NW Kii Peninsula

Kato

Hirajima

2017

Journal of Mineralogical and Petrological Sciences

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We report the new finding of barroisite (Brs)-bearing metabasites within a metabasite layer from the Kebara Formation, a unit exposed between the Sanbagawa and the Chichibu belts in NW Kii Peninsula. The dominant lithotype of the metabasite layer shows pale-green colors and is mainly composed of sodium amphibole, actinolite, pumpellyite and epidote. It is in agreement with reported mineral assemblages in the Kebara Formation which document pumpellyite-actinolite (PA) or pumpellyite-blueschist (PBS) facies conditions (<340°C and 0.8 GPa), and with geothermometry based on the Raman analysis of carbonaceous material from metapelite samples which give peak metamorphic temperatures of 300-340°C. Brs grains are identified from metabasites with dark-green color in the layer, and are closely associated with epidote, chlorite, white mica, albite and quartz, but not with pumpellyite. Brs grains are replaced by sodium amphibole and/or winchite at the rim with a distinct compositional gap. Thermodynamic calculation suggests that the Brs + epidote + chlorite + albite + quartz assemblage is stable at P-T conditions higher than 450°C and 0.4 GPa. The abovementioned data suggest that the Brs-bearing metabasites suffered an early higher temperature (>450°C) metamorphism and then overprinted by PA or PBS facies metamorphism along with the main constituents of the Kebara Formation. In the Besshi area of the Sanbagawa belt, the earlier subducted higher grade rocks are considered to juxtapose to the newly subducted rocks and overprinted retrograde metamorphism during their exhumation stage. Our new finding suggests that the similar phenomenon was took place in the lower grade part of the Sanbagawa belt.

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Section: Discussionsupporting

confidence: 86%

Section: Introductionmentioning

confidence: 99%

Petrology and possible significance of barroisite–bearing metabasite from the Kebara Formation in NW Kii Peninsula

Kato

Hirajima

2017

Journal of Mineralogical and Petrological Sciences

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“…The D 1 phase is characterized by ductile flow in an east-west direction, and during this phase of deformation the main foliation and lineation were formed. The lineation is defined by the shape-preferred orientation (SPO) of matrix amphiboles, which grew under retrograde conditions (Hara et al, 1990Wallis et al, 1992;Nakamura and Enami, 1994;Wintsch et al, 1999;Banno, 2000;Yagi and Takeshita, 2002;Toriumi, 2004, 2005), and by elongated quartz (Takeshita and Yagi, 2004), whereas the shape-preferred orientation of phengite and flattened quartz 8 define the foliation.…”

Section: Geological Settingmentioning

confidence: 99%

Coupled micro-faulting and pressure solution creep overprinted on quartz schist deformed by intracrystalline plasticity during exhumation of the Sambagawa metamorphic rocks, southwest Japan

Takeshita

El-Fakharani

2013

Journal of Structural Geology

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In the Sambagawa schist, southwest Japan, while ductile deformation pervasively occurred at D 1 phase during exhumation, low-angle normal faulting was locally intensive at D 2 phase under the conditions of frictional-viscous transition of quartz (c. 300 o C) during further exhumation into the upper crustal level. Accordingly, the formation of D 2 shear bands was overprinted on type I crossed girdle quartz c-axis fabrics and microstructures formed by intracrystalline plasticity at D 1 phase in some quartz schists. The quartz c-axis fabrics became weak and finally random with increasing shear, accompanied by the decreasing degree of undulation of recrystallized quartz grain boundaries, which resulted from the increasing portion of straight grain boundaries coinciding with the interfaces between newly precipitated quartz and mica. We interpreted these facts as caused by increasing activity of pressure solution: the quartz grains were dissolved mostly at platy quartz-mica interface, and precipitated with random orientation and pinned by mica, thus having led to the obliteration of existing quartz c-axis fabrics. In the sheared quartz schist, the strength became reduced by the enhanced pressure solution creep not only due to the reduction of diffusion path length caused by increasing number of shear bands, but also to enhanced dissolution at the interphase boundaries.

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“…Two metapelites (AS1919 and AS2006) and a metachert (ST22F04b) were collected from the albite-biotite zone of the Asemi-gawa (River Asemi) area (Higashino 1990;Otsuki and Banno 1990) and Saruta-gawa area (Kurata and Banno 1974;Banno 2000) in the inferred non-eclogite unit, respectively (Fig. 1a).…”

Section: Epidote-amphibolite Facies Rocksmentioning

confidence: 99%

Laser Raman microspectrometry of metamorphic quartz: A simple method for comparison of metamorphic pressures

Enami

Nishiyama

Mouri

2007

American Mineralogist

142

149

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A Laser Raman microspectrometry method was applied to metamorphic quartz in quartz-eclogite-, epidote-amphibolite-, and amphibolite-facies rocks to assess the quantitative correlation between the Raman frequency shift and metamorphic pressure. Quartz crystals sealed in garnet and other phases have a higher frequency shift than those in the matrix. Furthermore, the quartz inclusions show a frequency shift specifi c to the individual host crystals in eclogites (garnet ≈ kyanite > omphacite ≈ epidote). These observations imply that the residual pressures retained by quartz inclusions depend on elastic parameters of the host crystals, as discussed by previous researchers. The Raman frequency shift of quartz inclusions in garnet systematically increases with increasing peak metamorphic pressures from the amphibolite facies (0.30-0.55 GPa/470-570 °C), through the epidote-amphibolite facies (0.8-1.1 GPa/470-635 °C) to the quartz-eclogite facies (2.1-2.5 GPa/660-710 °C). Calibrations based on experimental work suggest that the measured Raman frequency shifts signify residual pressures of 0.1-0.2, 0.4-0.6, and 0.8-1.0 GPa for these three groups of metamorphic rocks, respectively. Normal stresses (internal pressures) of quartz inclusions in garnet, numerically simulated with an elastic model, and inferred pressure-temperature conditions at peak metamorphic stage are compatible with the residual pressures estimated from the frequency shifts. Laser Raman microspectroscopic analysis of quartz is a simple and effective method for (1) comparison of pressure conditions in metamorphic rocks formed under various pressure-temperature conditions, and (2) detection of a higher-pressure signature in metamorphic rocks extensively recrystallized during the subsequent exhumation and hydration stage.

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Intermediate high-pressure exhumation of the northern segment of the Sanbagawa belt, Saruta-gawa area, central Shikoku, Japan

Cited by 23 publications

References 25 publications

Petrology and possible significance of barroisite–bearing metabasite from the Kebara Formation in NW Kii Peninsula

Petrology and possible significance of barroisite–bearing metabasite from the Kebara Formation in NW Kii Peninsula

Coupled micro-faulting and pressure solution creep overprinted on quartz schist deformed by intracrystalline plasticity during exhumation of the Sambagawa metamorphic rocks, southwest Japan

Laser Raman microspectrometry of metamorphic quartz: A simple method for comparison of metamorphic pressures

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