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New calibration of infrared measurement of dissolved water in rhyolitic glasses

Zhang, Youxue and Belcher, R. and Ihinger, P. D. and Wang, Liping and Xu, Zhengjiu and Newman, S. (1997) New calibration of infrared measurement of dissolved water in rhyolitic glasses. Geochimica et Cosmochimica Acta, 61 (15). pp. 3089-3100. ISSN 0016-7037. doi:10.1016/s0016-7037(97)00151-8.

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This paper presents a new calibration for infrared analyses of dissolved water and its species concentrations in rhyolitic glasses. The new calibration combines infrared/manometry measurements and infrared study of hydrous rhyolitic glasses heated at different temperatures. The heating experiments show that the ratio of the molar absorptivity of the 5230 cm^(−1) band to that of the 4520 cm^(−1) band varies with water concentration. Therefore, earlier calibrations assuming constant molar absorptivities are not accurate. Using our new calibration, total water concentration, and species concentrations can be calculated as follows: (ƍƍ_0)C_1 = a_(0-523); (ƍƍ_0)C_2 = (b_0 + b_(1-523) + b_(2-452)_452, ardC = C_1 + C_2, where C_1, C_2, and C are the mass fractions of molecular H_2O, H_2O present as OH, and total H_2O, πƍ_0 is the ratio of the density of the hydrous glass to that of the anhydrous glass and is approximately 1 - C, _(523) and _(452) are the absorbances (peak heights) of the 5230 cm^(−1) and 4520 cm^(−1) bands per mm sample thickness and relative to a baseline that was fit by a flexicurve, a_0 = 0.04217 mm, b_0 = 0.04024 mm, _1 = −0.02011 mm^2, and b_2 = 0.0522 mm^2. The new calibration has a high internal reproducibility in calculating H_2O_(total), six times better than the calibration of Newman et al. (1986). We expect the new calibration to be accurate in retrieving H_2O_(total) for H_2O_(total) ≤ 5.5 wt% and in retrieving molecular H_2O and OH concentrations for H_2O_(total) ≤ 2.7 wt%. Using the new calibration, the equilibrium coefficient K for the reaction H_2O + O = 2OH is independent of H_2O_(total) (for H_2O_(total) ≤ 2.4 wt%) at a given temperature and can be expressed as ln K = 1.876 - 3110T, where T is in K. The bulk water diffusivity reported before is not affected by the new calibration, but the molecular H_2O diffusivity will be roughly 4–30% greater.

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Zhang, Youxue0000-0002-7439-0086
Newman, S.0000-0003-0710-995X
Additional Information:© 1997 Published by Elsevier. (Received December 10, 1996; accepted in revised form April 1, 1997) Glass inclusions in quartz phenocrysts from the Bishop Tuff and Mono ash flows were prepared and provided by A. T. Anderson with help from Nathaniel Brown. We greatly appreciate their generous help. We thank A. T. Anderson and P. F. McMillan for constructive comments. This work was supported by NSF grants EAR-9315918 and EAR-9458368.
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Issue or Number:15
Record Number:CaltechAUTHORS:20181016-153903141
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Official Citation:Youxue Zhang, R. Belcher, P.D. Ihinger, Liping Wang, Zhengjiu Xu, S. Newman, New calibration of infrared measurement of dissolved water in rhyolitic glasses, Geochimica et Cosmochimica Acta, Volume 61, Issue 15, 1997, Pages 3089-3100, ISSN 0016-7037, (
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:90296
Deposited By: George Porter
Deposited On:22 Oct 2018 15:25
Last Modified:16 Nov 2021 03:31

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