Calibration of the infrared molar absorption coefficients for H in olivine, clinopyroxene and rhyolitic glass by elastic recoil detection analysis

Cyril Aubaud, Hélène Bureau, Caroline Raepsaet, Hicham Khodja, Anthony C. Withers, Marc M. Hirschmann, David R. Bell

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21 Scopus citations

Abstract

We use a nuclear microbeam technique (Elastic Recoil Detection Analysis or ERDA) to measure the H content in 2 rhyolitic glasses, 4 olivines, 4 orthopyroxenes, and 7 clinopyroxenes. These samples have been characterized previously for their OH absorption spectra by infrared (FTIR) spectroscopy. We use ERDA and FTIR data to calibrate the infrared molar absorption coefficients. The blank level of the ERDA method is 102±81ppm H2O, too great for the analysis of many natural nominally anhydrousminerals (NAMs) fromthe uppermantle, but applicable to H-rich glasses, natural and synthetic NAMs. Calibration of the molar absorption coefficient ε with the ERDA results gives 95±8 l mol-1 cm-1 for rhyolitic glasses (peak height), 34,515±7050 l mol-1 cm-2 for olivine and 46,103±5300 l mol-1 cm-2 for clinopyroxene (integrated area). The olivine calibration of the present study is intermediate between that of Bell et al. [Bell, D.R., Rossman,G.R.,Maldener, J.,Endisch,D. and Rauch, F.,2003.Hydroxide in olivine: a quantitative determination of the absolute amount and calibration of the IR spectrum. Journal of Geophysical Research, 108(B2). doi:10.1029/2001JB000679] and that of Libowitzky and Rossman [Libowitzky, E. and Rossman, G.R., 1997. An IR absorption calibration for water in minerals. American Mineralogist, 82: 1111-1115]. For clinopyroxene, the best agreement with the ERDA data is obtained for the Libowitzky and Rossman [Libowitzky, E. and Rossman, G.R., 1997. An IR absorption calibration forwater in minerals. AmericanMineralogist, 82: 1111-1115] calibration (5% lower than the ERDA data). The present calibration also confirms that the Paterson [Paterson, M.S., 1982. The determination of hydroxyl by infrared absorption inquartz, silicate glasses and similarmaterials. Bulletin deMineralogie,105: 20-29] calibration systematically underestimates the OH content in olivine.

Original languageEnglish (US)
Pages (from-to)78-86
Number of pages9
JournalChemical Geology
Volume262
Issue number1-2
DOIs
StatePublished - May 2009

Keywords

  • Detection analysis
  • Elastic recoil
  • Infrared spectroscopy
  • Nominally anhydrous minerals
  • Volcanic glasses
  • Water

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