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Formation of Fe- and Mg-Rich Smectite under Hyperalkaline Conditions at Narra in Palawan, the Philippines

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Title: Formation of Fe- and Mg-Rich Smectite under Hyperalkaline Conditions at Narra in Palawan, the Philippines
Authors: Shimbashi, Misato Browse this author
Sato, Tsutomu Browse this author →KAKEN DB
Yamakawa, Minoru Browse this author
Fujii, Naoki Browse this author
Otake, Tsubasa Browse this author
Keywords: Fe- and Mg-rich smectite
alkaline
ophiolite
M-S-H
F-S-H
C-S-H
geological disposal
natural analogue
Mars
Issue Date: 12-Apr-2018
Publisher: MDPI
Journal Title: Minerals
Volume: 8
Issue: 4
Start Page: 155
Publisher DOI: 10.3390/min8040155
Abstract: The formation of Fe- and Mg-rich smectite and zeolite under alkaline conditions, as secondary minerals after the alkaline alteration of bentonite in repositories for radioactive waste, is of major concern. It is crucial for safety assessments to know whether smectite is formed as a secondary mineral after the alkaline alteration of bentonite. In the present paper, Fe- and Mg-rich smectite, which interacted with the hyperalkaline groundwater at Narra in Palawan, Philippines, was used. Mineralogical and geochemical investigation was conducted to understand the formation process of the smectite and the factors determining the formation of secondary mineral species. The results suggest that a certain amount of smectite may be generated under hyperalkaline conditions, by alteration from amorphous or poorly crystalline components such as M-S-H and F-S-H. Therefore, the controlling factor determining whether smectite or zeolite will be generated as secondary minerals after alkaline alteration of bentonite could be whether nuclei of M-S-H and/or F-S-H are formed. Whether such formation takes place may be determined by the presence of dissolved Mg2+ and Fe2+ in the environment. The formation process of smectite under alkaline conditions, suggested by the results here, is analogous to the generally accepted model of smectite formation as it may have occurred on early Mars.
Rights: © 2018 by the authors; licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0/).
http://creativecommons.org/licenses/by/4.0/
Type: article
URI: http://hdl.handle.net/2115/70158
Appears in Collections:工学院・工学研究院 (Graduate School of Engineering / Faculty of Engineering) > 雑誌発表論文等 (Peer-reviewed Journal Articles, etc)

Submitter: 佐藤 努

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