Infrared spectroscopy of hydrous glasses of arc magma compositions

Molar absorption coefficients of water in glasses of are magma compositions have been determined for similar to 2.8 mu m, similar to 2.2 mu m, and similar to 1.9 mu m bands. Excellent agreement was found between the water contents calculated from the absorption peak heights and those determined by H-2 manometry when the following molar absorption coefficients (m(3)/mol m) are used for different glass compositions: epsilon(2.8 mu m) = 6.4 +/- 0.1, epsilon(2.2 mu m) = 0.085 +/- 0.007, and epsilon(1.9 mu m) = 0.084 +/- 0.006 for tholeiite and high-Al basalt glasses; epsilon(2.8 mu m) = 6.8 +/- 0.1, epsilon(2.2 mu m) = 0.094 +/- 0.006, and epsilon(1.9 mu m) = 0.16 +/- 0.03 for dacite glass. With IR spectroscopy using these coefficients, water concentrations up to similar to 3 wt. % in the are basalt and dacite glasses can be determined accurately.