A new approach was developed to measure the water content of silicate
glasses using Raman spectroscopy, which is independent of the glass
matrix composition and structure. Contrary to previous studies, the
compositional range of our studied silicate glasses was not restricted
to rhyolites, but included andesitic, basaltic and phonolitic glasses.
We used 21 glasses with known water contents for calibration. To reduce
the uncertainties caused by the baseline removal and correct for the
influence of the glass composition on the spectra, we developed the
following strategy: (1) application of a frequency-dependent intensity
correction of the Raman spectra; (2) normalization of the water peak
using the broad T-O and T-O-T vibration band at 850-1250 cm(-1)
wavenumbers (instead of the low wavenumber T-O-T broad band, which
appeared to be highly sensitive to the FeO content and the degree of
polymerization of the melt); (3) normalization of the integrated Si-O
band area by the total number of tetrahedral cations and the position
of the band maximum. The calibration line shows a +/- 0.4 wt%
uncertainty at one relative standard deviation in the range of 0.8-9.5
wt% water and a wide range of natural melt compositions. This method
provides a simple, quick, broadly available and cost-effective way for
a quantitative determination of the water content of silicate glasses.
Application to silicate melt inclusions yielded data in good agreement
with SIMS data.