2011年6月
Reaction microstructures in corundum- and kyanite-bearing mafic mylonites from the Takahama metamorphic rocks, western Kyushu, Southwest Japan
ISLAND ARC
- ,
- ,
- 巻
- 20
- 号
- 2
- 開始ページ
- 248
- 終了ページ
- 258
- 記述言語
- 英語
- 掲載種別
- 研究論文(学術雑誌)
- DOI
- 10.1111/j.1440-1738.2011.00763.x
- 出版者・発行元
- WILEY-BLACKWELL
High-grade mylonites occur in the Takahama metamorphic rocks, a member of the high-pressure low-temperature type Nagasaki Metamorphic Rocks, western Kyushu, Japan. Mafic layers within the mylonites retain reaction microstructures consisting of margarite aggregates armoring both corundum and kyanite. The following retrograde reaction well accounts for the microstructures in the CaO-Al(2)O(3)-SiO(2)-H(2)O system: 3Al(2)O(3) + 2Al(2)SiO(5) + 2Ca(2)Al(3)Si(3)O(12)(OH) + 3H(2)O = 2Ca(2)Al(8)Si(4)O(20)(OH)(4) (corundum + kyanite + clinozoisite + fluid = margarite). Mass balance analyses and chemical potential modeling reveal that the chemical potential gradients present between kyanite and corundum have likely driven the transport of the CaO and SiO(2) components. The mylonitization is considered to take place chronologically after peak metamorphism and before the above reaction, based on the following features: approximately constant thickness of the margarite aggregates, random orientation of margarite, and local modification of garnet composition at a boudin neck that formed during mylonitization. The estimated peak temperature of 640 degrees C and the pressure-temperature conditions of the above reaction indicate that the mylonitization took place at temperature between 530 and 640 degrees C at pressures higher than 1.2 GPa, approximately equivalent to the depth of the lower crust of island arcs.
- リンク情報
- ID情報
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- DOI : 10.1111/j.1440-1738.2011.00763.x
- ISSN : 1038-4871
- ORCIDのPut Code : 45377595
- Web of Science ID : WOS:000291043400007