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Journal of Zhejiang University SCIENCE A 2005 Vol.6 No.7 P.649-655


Petrological study of the western Iratsu mass from the Sambagawa metamorphic belt, central Shikoku, Japan

Author(s):  LI Zi-long, TAKASU Akira

Affiliation(s):  Department of Earth Science, Zhejiang University, Hangzhou 310027, China; more

Corresponding email(s):   zilongli@zju.edu.cn

Key Words:  Petrology, P-T-t path, Western Iratsu mass, Sambagawa belt

LI Zi-long, TAKASU Akira. Petrological study of the western Iratsu mass from the Sambagawa metamorphic belt, central Shikoku, Japan[J]. Journal of Zhejiang University Science A, 2005, 6(7): 649-655.

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author="LI Zi-long, TAKASU Akira",
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%T Petrological study of the western Iratsu mass from the Sambagawa metamorphic belt, central Shikoku, Japan
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%J Journal of Zhejiang University SCIENCE A
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T1 - Petrological study of the western Iratsu mass from the Sambagawa metamorphic belt, central Shikoku, Japan
A1 - LI Zi-long
A1 - TAKASU Akira
J0 - Journal of Zhejiang University Science A
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%@ 1673-565X
Y1 - 2005
PB - Zhejiang University Press & Springer
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DOI - 10.1631/jzus.2005.A0649

The western Iratsu mass, the largest tectonic body in the Sambagawa metamorphic belt, central Shikoku, is mainly composed of epidote amphibolite with minor amounts of eclogite. Systematically, a majority of garnets show bell-shaped chemical zoning of pyrope contents and Mg/(Mg+Fe2+) monotonously increasing outward. The grossular component in zonal garnet increases outwards, maximizes at an intermediate part, and then decreases towards the outermost rim, reflecting a process from increasing to decreasing pressure conditions during the prograde metamorphism. Jadeite contents of omphacite range from 25~20 mole% within the cores to 15~10 mole% at the rims, implying a pressure-decreasing process (from 11×105 Pa to 8×105 Pa). The peak pressure-temperature (P-T) condition of 630~680 °C and ca. 15×105 Pa in the western Iratsu mass is much higher than that of (610±25) °C and (10±1)×105 Pa of the Sambagawa oligoclase-biotite zone schists. The authors suggest a clockwise p-T-t path for the western Iratsu mass.

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