| Petrological study of the western Iratsu mass from the Sambagawa metamorphic belt, central Shikoku, Japan |
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| 作者姓名： | 厉子龙 TAKASU Akira |
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| 作者单位： | Department of Earth Science Zhejiang University，Department of Earth Science Shimane University Hangzhou 310027，China，Matsue 690，Japan |
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| 摘 要： | 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 25～20mole% 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 ℃ and ca. 15× 105 Pa in the western Iratsu mass is much higher than that of (610±25) ℃ 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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| 关 键 词： | 岩石学 变质结构 硬玉 绿辉石 片岩 |
| 收稿时间： | 2005-03-16 |
| 修稿时间： | 2005-05-10 |
Petrological study of the western iratsu mass from the Sambagawa metamorphic belt, central Shikoku, Japan |
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| 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,2005,6(7):649-655. |
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| Authors: | Li Zi-long Takasu Akira |
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| Institution: | (1) Department of Earth Science, Zhejiang University, 310027 Hangzhou, China;(2) Department of Earth Science, Shimane University, 690 Matsue, Japan |
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| Abstract: | 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.
Project supported by the National Natural Science Foundation of China (No. 40472040) and Starting Fund of Education Ministry,
China |
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| Keywords: | Petrology P-T-t path Western Iratsu mass Sambagawa belt |
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