Preprint Article Version 1 This version is not peer-reviewed

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

Version 1 : Received: 16 February 2018 / Approved: 16 February 2018 / Online: 16 February 2018 (15:30:00 CET)

A peer-reviewed article of this Preprint also exists.

Shimbashi, M.; Sato, T.; Yamakawa, M.; Fujii, N.; Otake, T. Formation of Fe- and Mg-Rich Smectite under Hyperalkaline Conditions at Narra in Palawan, the Philippines. Minerals 2018, 8, 155. Shimbashi, M.; Sato, T.; Yamakawa, M.; Fujii, N.; Otake, T. Formation of Fe- and Mg-Rich Smectite under Hyperalkaline Conditions at Narra in Palawan, the Philippines. Minerals 2018, 8, 155.

Journal reference: Minerals 2018, 8, 155
DOI: 10.3390/min8040155

Abstract

Formation of Fe- and Mg-rich smectite and zeolite under alkaline conditions is concerned as secondary minerals after alkaline alteration of bentonite in a repository of radioactive wastes. It might be crucial for safety assessment whether smectite will be formed or not as secondary minerals after alkaline alteration of bentonite. In present paper, Fe- and Mg-rich smectite which are currently interacting with hyperalkaline groundwater was found at Narra in Palawan, Philippines. Mineralogical and geochemical investigation was conducted to understand formation process of smectite and factors determined secondary mineral species. Our study revealed a certain amount of smectite may have been produced under hyperalkaline conditions, altered from amorphous or poorly crystalline material such as M-S-H and F-S-H. Key factor which decides smectite or zeolite as secondary minerals after alkaline alteration of bentonite might be whether nuclei of M-S-H and/or F-S-H will be formed or not. This might be decided by the presence of dissolved Mg2+ and Fe2+ in the system. Our suggested formation process of smectite under alkaline conditions is analogue with generally-accepted model of smectite formation that might have been occurred on early Mars.

Subject Areas

Fe- and Mg-rich smectite; alkaline; ophiolite; M-S-H; F-S-H; C-S-H; geological disposal; natural analogue; Mars

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