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Water diffusion in silica glass through pathways formed by hydroxyls

Minami Kuroda, Shogo Tachibana, Naoya Sakamoto, Satoshi Okumura, Michihiko Nakamura and Hisayoshi Yurimoto
Water diffusion in silica glass through pathways formed by hydroxyls
American Mineralogist (March 2018) 103 (3): 412-417


Water diffusion in silicate melts is a fundamental process controlling physical and chemical consequences for magmatism, but mechanisms of diffusion in silicate glasses and melts are not fully understood. In this study, water diffusion experiments in silica glass were performed at temperatures of 650-850 degrees C and water vapor pressure of 50 bar, with the aim of improving our understanding of the mechanism of water diffusion in a simple SiO (sub 2) -H (sub 2) O system, and to construct a general water diffusion model for multi-component silicate glasses. Hydrogen diffusion profiles in silica glass were measured by secondary ion mass spectrometry (SIMS) down to a water concentration of approximately 10 ppm. Water diffusion profiles indicate that water diffusion becomes slower with decreasing water concentration in silica glass, with the water concentration dependence being greater than in multi-component silicate glasses, particularly at low concentrations (e.g., Doremus 1969, 2000; Zhang and Behrens 2000). A new water diffusion model is proposed for silica glass, where the greater concentration dependence is attributed to the limited number of diffusion pathways in silica glass, formed by breaking Si-O-Si bonds through hydroxyl formation. The model was applied to multi-component silicate glasses, taking into account the effects of metal cations that act as network modifiers by providing additional diffusion pathways for water molecules. The lower water concentration dependence in multi-component silicate glasses and melts is explained by little dependence of the number of diffusion pathways on water concentration because it is controlled extrinsically by network modifier cations. It is concluded that the number of diffusion pathways is an essential controlling factor for water diffusion in silica and silicate glasses.

ISSN: 0003-004X
EISSN: 1945-3027
Serial Title: American Mineralogist
Serial Volume: 103
Serial Issue: 3
Title: Water diffusion in silica glass through pathways formed by hydroxyls
Affiliation: Hokkaido University, Department of Natural History Sciences, Sapporo, Japan
Pages: 412-417
Published: 201803
Text Language: English
Publisher: Mineralogical Society of America, Washington, DC, United States
References: 32
Accession Number: 2018-033681
Categories: Igneous and metamorphic petrology
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 1 table
Secondary Affiliation: University of Tokyo, JPN, JapanTohoku University, JPN, JapanJapan Aerospace Exploration Agency, JPN, Japan
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2018, American Geosciences Institute. Abstract, copyright, Mineralogical Society of America. Reference includes data from GeoScienceWorld, Alexandria, VA, United States
Update Code: 201808
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