Details
| Original language | English |
|---|---|
| Pages (from-to) | 5-20 |
| Number of pages | 16 |
| Journal | Chemical Geology |
| Volume | 174 |
| Issue number | 1-3 |
| Early online date | 23 Feb 2001 |
| Publication status | Published - 1 Apr 2001 |
Abstract
Molar absorption coefficients (molar absorptivities) of the near infrared combination bands at 4500 and 5200 cm-1 assigned to OH groups and H2O molecules, respectively, were determined for glasses of dacitic, andesitic and basaltic compositions. Total water contents (range 1.5-6.3 wt.%) of the samples used in the calibration were determined by pyrolysis and subsequent Karl-Fischer Titration. Different combinations of baseline types and intensity measure (peak height/area) were applied to investigate the effect of evaluation procedure on infrared spectroscopic determination of apparent species concentrations and total water. The best reproducibility of total water was obtained by modeling the baseline of the combination bands by two gaussians at ∼ 5700 and ∼ 4000 cm-1 (GG type baseline) and evaluating peak heights (maximum deviation of ±0.17 wt.% water). Plots of normalized absorbances are consistent with identical ratios of the absorption coefficients, εH2O/εOH, for dacitic, andesitic and basaltic compositions as well as for a rhyolitic composition (data from Withers and Behrens [Withers, A.C., Behrens, H., 1999. Temperature induced changes in the NIR spectra of hydrous albitic and rhyolitic glasses between 300 and 100 K. Phys. Chem. Minerals, 27, 119-132]). A parabolic equation is proposed to predict the molar linear and integrated absorption coefficients as a function of the SiO2 content of the glass within the range of water contents used in the calibration. For example, using the GG type baseline and evaluating peak heights, we obtained εH2O/εOH = 1.13 and εH2O [in 1 mol-1 cm-1] = 2.290 x 10-4 x (wt.% SiO2)2. At a given water content and quench rate, OH concentrations are higher in andesitic than dacitic glasses which is consistent with higher fictive temperatures of hydrous andesitic glasses containing more than 1.5 wt.% water.
Keywords
- Absorption coefficient, Andesite, Basalt, Dacite, Infrared spectroscopy, Rhyolite, Water
ASJC Scopus subject areas
- Earth and Planetary Sciences(all)
- Geology
- Earth and Planetary Sciences(all)
- Geochemistry and Petrology
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In: Chemical Geology, Vol. 174, No. 1-3, 01.04.2001, p. 5-20.
Research output: Contribution to journal › Article › Research › peer review
}
TY - JOUR
T1 - Compositional dependence of molar absorptivities of near-infrared OH-and H2O bands in rhyolitic to basaltic glasses
AU - Ohlhorst, Susanne
AU - Behrens, Harald
AU - Holtz, François
N1 - Funding Information: This work was supported by the ICDP program (project HO 1337/3-1) of the German Science Foundation (DFG). Technical assistance has been provided by Otto Dietrich, Willi Hurckuck and Vanessa Kunde. We thank Jasper Berndt for providing us the basalt samples. The critical reviews of Nathalie Jendrzejewski and an anonymous reviewer helped to improve the manuscript. Copyright: Copyright 2011 Elsevier B.V., All rights reserved.
PY - 2001/4/1
Y1 - 2001/4/1
N2 - Molar absorption coefficients (molar absorptivities) of the near infrared combination bands at 4500 and 5200 cm-1 assigned to OH groups and H2O molecules, respectively, were determined for glasses of dacitic, andesitic and basaltic compositions. Total water contents (range 1.5-6.3 wt.%) of the samples used in the calibration were determined by pyrolysis and subsequent Karl-Fischer Titration. Different combinations of baseline types and intensity measure (peak height/area) were applied to investigate the effect of evaluation procedure on infrared spectroscopic determination of apparent species concentrations and total water. The best reproducibility of total water was obtained by modeling the baseline of the combination bands by two gaussians at ∼ 5700 and ∼ 4000 cm-1 (GG type baseline) and evaluating peak heights (maximum deviation of ±0.17 wt.% water). Plots of normalized absorbances are consistent with identical ratios of the absorption coefficients, εH2O/εOH, for dacitic, andesitic and basaltic compositions as well as for a rhyolitic composition (data from Withers and Behrens [Withers, A.C., Behrens, H., 1999. Temperature induced changes in the NIR spectra of hydrous albitic and rhyolitic glasses between 300 and 100 K. Phys. Chem. Minerals, 27, 119-132]). A parabolic equation is proposed to predict the molar linear and integrated absorption coefficients as a function of the SiO2 content of the glass within the range of water contents used in the calibration. For example, using the GG type baseline and evaluating peak heights, we obtained εH2O/εOH = 1.13 and εH2O [in 1 mol-1 cm-1] = 2.290 x 10-4 x (wt.% SiO2)2. At a given water content and quench rate, OH concentrations are higher in andesitic than dacitic glasses which is consistent with higher fictive temperatures of hydrous andesitic glasses containing more than 1.5 wt.% water.
AB - Molar absorption coefficients (molar absorptivities) of the near infrared combination bands at 4500 and 5200 cm-1 assigned to OH groups and H2O molecules, respectively, were determined for glasses of dacitic, andesitic and basaltic compositions. Total water contents (range 1.5-6.3 wt.%) of the samples used in the calibration were determined by pyrolysis and subsequent Karl-Fischer Titration. Different combinations of baseline types and intensity measure (peak height/area) were applied to investigate the effect of evaluation procedure on infrared spectroscopic determination of apparent species concentrations and total water. The best reproducibility of total water was obtained by modeling the baseline of the combination bands by two gaussians at ∼ 5700 and ∼ 4000 cm-1 (GG type baseline) and evaluating peak heights (maximum deviation of ±0.17 wt.% water). Plots of normalized absorbances are consistent with identical ratios of the absorption coefficients, εH2O/εOH, for dacitic, andesitic and basaltic compositions as well as for a rhyolitic composition (data from Withers and Behrens [Withers, A.C., Behrens, H., 1999. Temperature induced changes in the NIR spectra of hydrous albitic and rhyolitic glasses between 300 and 100 K. Phys. Chem. Minerals, 27, 119-132]). A parabolic equation is proposed to predict the molar linear and integrated absorption coefficients as a function of the SiO2 content of the glass within the range of water contents used in the calibration. For example, using the GG type baseline and evaluating peak heights, we obtained εH2O/εOH = 1.13 and εH2O [in 1 mol-1 cm-1] = 2.290 x 10-4 x (wt.% SiO2)2. At a given water content and quench rate, OH concentrations are higher in andesitic than dacitic glasses which is consistent with higher fictive temperatures of hydrous andesitic glasses containing more than 1.5 wt.% water.
KW - Absorption coefficient
KW - Andesite
KW - Basalt
KW - Dacite
KW - Infrared spectroscopy
KW - Rhyolite
KW - Water
UR - http://www.scopus.com/inward/record.url?scp=0035095534&partnerID=8YFLogxK
U2 - 10.1016/S0009-2541(00)00303-X
DO - 10.1016/S0009-2541(00)00303-X
M3 - Article
AN - SCOPUS:0035095534
VL - 174
SP - 5
EP - 20
JO - Chemical Geology
JF - Chemical Geology
SN - 0009-2541
IS - 1-3
ER -