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March 8, 2010

Determination of molar absorptivities for infrared absorption bands of H2O in andesitic glasses

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We have determined infrared molar absorptivities for water absorption bands in Fe-bearing and Fe-free andesitic glasses. Water dissolves in andesitic glasses as both hydroxyl groups and molecular water as observed in other silicate glasses. Concentrations of molecular water and hydroxyl species are a strong function of total water content. IR molar absorptivities for Fe-bearing andesite are 3570 = 62.32 ± 0.42 L/mol·cm, 4500 = 0.79 ± 0.07 L/mol·cm, 5200 = 1.07 ± 0.07 L/mol·cm, and 1630 = 42.34 ± 2.77 L/mol·cm. Molar absorptivities for Fe-free andesite are 69.21 ± 0.52 L/mol·cm for 3570, 0.89 ± 0.07 L/mol·cm for 4500, 1.46 ± 0.07 L/mol·cm for 5200, and 52.05 ± 2.85 L/mol·cm for 1630. Molar absorptivities show significant compositional dependencies that can be predicted based on tetrahedral cation (Si+4, Al+3)/total cation fraction.
Charles W. Mandeville1,*, James D. Webster1, Malcolm J. Rutherford2, Bruce E. Taylor3, Adrian Timbal3 and Kevin Faure4
1 American Museum of of Natural History, Central Park West at 79th St. New York, New York 10024-5192, U.S.A.
2 Department of Geological Sciences, Brown University, Box 1846, Providence, Rhode Island 02912, U.S.A.
3 Geological Survey of Canada, 601 Booth Street, Ottawa, Ontario K1A0E8, Canada
4 Institute of Geological & Nuclear Sciences, 30 Gracefield Rd. Lower Hutt, New Zealand

Correspondence: * E-mail: cmandy@amnh.org

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