2002•American MineralogistRequires access
Determination of molar absorptivities for infrared absorption bands of H 2 O in andesitic glasses
Charles W. Mandeville, James D. Webster, M. J. Rutherford, Bruce E. Taylor, A. Timbal, Kevin Faure
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Abstract
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 ε 3570 = 62.32 ± 0.42 L/mol·cm, ε 4500 = 0.79 ± 0.07 L/mol·cm, ε 5200 = 1.07 ± 0.07 L/mol·cm, and ε 1630 = 42.34 ± 2.77 L/mol·cm. Molar absorptivities for Fe-free andesite are 69.21 ± 0.52 L/mol·cm for e3570, 0.89 ± 0.07 L/mol·cm for e4500, 1.46 ± 0.07 L/mol·cm for e5200, and 52.05 ± 2.85 L/mol·cm for ε 1630 . Molar absorptivities show significant compositional dependencies that can be predicted based on tetrahedral cation (Si +4 , Al +3 )/total cation fraction