Determination of the concentration of water dissolved in glasses and minerals using nuclear microprobe

In Earth Sciences, the global water cycle is of fundamental importance. For this reason, the H2O content of volcanic glass and mantle minerals must be analysed: usually by micro-infrared spectroscopy (FTIR) or secondary ion mass spectrometry (SIMS). However, both of these methods require calibration using standards of known water content. To avoid matrix effects, the standards and unknowns must be otherwise identical in composition. In this study we have determined the water content of geological samples, in the range 10 ppm-5wt%H2O, using an absolute analytical technique: a combination of elastic recoil detection analysis (ERDA) and Rutherford backscattering spectrometry (RBS). We compared the results obtained by this method to data obtained by FTIR on the same samples. We discuss the limitations of the method and use the results to calibrate IR extinction coefficients for FTIR spectroscopy. (C) 2003 Elsevier B.V. All rights reserved.