Work

Hydrogen concentration analyses using SIMS and FTIR: Comparison and calibration for nominally anhydrous minerals

Year: 2003

Type: article

Abstract: We report analyses of hydrogen abundance in experimentally annealed and natural mantle minerals using FTIR and use these data to establish calibration lines for measurement of H 2 O concentrations in olivine, pyroxenes, garnet, amphibole and mica by secondary ion mass spectrometry (SIMS). We have reduced the detection limit for H 2 O analysis by SIMS to 2–4 ppm H 2 O (by weight) through careful attention to sample preparation and vacuum quality. The accuracy of the SIMS calibrations depends on the choice of FTIR extinction coefficients; however, all of the calibrations reported here are shown to be consistent with measurements on standards whose H 2 O abundance has been determined independently via manometry or nuclear reaction analysis. The resulting calibrations are accurate to 10–30% at the 95% confidence limit, with improvements possible through the use of higher‐H 2 O standards. Using our SIMS calibration, we determined hydrogen concentrations in coexisting olivine, orthopyroxene, and glass from a single melting experiment at 2 GPa and 1380°C. Olivine/melt and orthopyroxene/melt partition coefficients are equal to 0.0020 ± 0.0002 and 0.0245 ± 0.0015, respectively, and the orthopyroxene/olivine coefficient is 12 ± 4 (2σ uncertainties).

Source: Geochemistry Geophysics Geosystems

DOI: 10.1029/2002gc000378

Authors: Kenneth Koga, Erik Hauri, Marc Hirschmann, David Bell