Mantle wedge infiltrated with saline fluids from dehydration and decarbonation of subducting slab
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- Tatsuhiko Kawamoto
- Institute for Geothermal Sciences, Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan;
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- Masako Yoshikawa
- Institute for Geothermal Sciences, Graduate School of Science, Kyoto University, Beppu 874-0903, Japan;
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- Yoshitaka Kumagai
- Institute for Geothermal Sciences, Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan;
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- Ma. Hannah T. Mirabueno
- Philippine Institute of Volcanology and Seismology, University of the Philippines, Quezon City 1101, Philippines;
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- Mitsuru Okuno
- Department of Earth System Science, Faculty of Science, Fukuoka University, Fukuoka 814-0180, Japan; and
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- Tetsuo Kobayashi
- Department of Earth and Environmental Sciences, Graduate School of Science and Engineering, Kagoshima University, Kagoshima 890-0065, Japan
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説明
<jats:p> Slab-derived fluids play an important role in heat and material transfer in subduction zones. Dehydration and decarbonation reactions of minerals in the subducting slab have been investigated using phase equilibria and modeling of fluid flow. Nevertheless, direct observations of the fluid chemistry and pressure–temperature conditions of fluids are few. This report describes CO <jats:sub>2</jats:sub> -bearing saline fluid inclusions in spinel-harzburgite xenoliths collected from the 1991 Pinatubo pumice deposits. The fluid inclusions are filled with saline solutions with 5.1 ± 1.0% (wt) NaCl-equivalent magnesite crystals, CO <jats:sub>2</jats:sub> -bearing vapor bubbles, and a talc and/or chrysotile layer on the walls. The xenoliths contain tremolite amphibole, which is stable in temperatures lower than 830 °C at the uppermost mantle. The Pinatubo volcano is located at the volcanic front of the Luzon arc associated with subduction of warm oceanic plate. The present observation suggests hydration of forearc mantle and the uppermost mantle by slab-derived CO <jats:sub>2</jats:sub> -bearing saline fluids. Dehydration and decarbonation take place, and seawater-like saline fluids migrate from the subducting slab to the mantle wedge. The presence of saline fluids is important because they can dissolve more metals than pure H <jats:sub>2</jats:sub> O and affect the chemical evolution of the mantle wedge. </jats:p>
収録刊行物
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- Proceedings of the National Academy of Sciences
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Proceedings of the National Academy of Sciences 110 (24), 9663-9668, 2013-05-28
Proceedings of the National Academy of Sciences