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Published January 1986 | public
Journal Article

Dissolved carbon dioxide in basaltic glasses: concentrations and speciation


Carbon dioxide dissolved in both synthetic Ca±Mg-bearing silicate glasses and natural basaltic glasses has been characterized using infrared spectroscopy. CO_2 is inferred to be dissolved in these glasses as distorted Ca or Mg carbonate ionic complexes that result in unique infrared absorption bands at 1515 cm^(−1) and 1435 cm^(−1). This speciation contrasts with the case of CO_2-bearing sodium aluminosilicate glasses, which contain both dissolved molecular CO_2 and dissolved Na-carbonate ionic-complexes. The difference in speciation in Ca±Mg-bearing melts may result in part from a higher activity of oxygens that react with CO_2 molecules to produce carbonate. Dissolved CO_2 contents of natural basaltic glasses can be determined from the intensities of the carbonate absorption bands at 1515 cm^(−1) and 1435 cm^(−1). The uncertainty of the method is estimated to be ± 15% of the amount present. The infrared technique is a powerful tool for the measurement of dissolved CO_2 contents in natural basaltic glasses since it is non-destructive, can be aimed at regions of glass a few tens of microns in size, and can discriminate between dissolved carbonate and carbon present as carbonate alteration, contained in fluid inclusions, or adsorbed on the glass. A set of submarine basaltic glasses dredged from a variety of locations contain 0–400 ppm dissolved CO_2, measured using the infrared technique. These concentrations are lower than most previous reports for similar basaltic glasses. No general relationship is observed between dissolved CO_2 content and depth of magmatic eruption, although some correlation might be present in restricted geographic locales.

Additional Information

© 1986 Elsevier B.V. Received 5 July 1985. Revised 10 October 1985. We thank Professor George Rossman for the use of the infrared spectrophotometer and for his guidance. Professor T. Tombrello and Drs. M. Mendenhall and R. Livi are also thanked for their help analyzing C using nuclear reaction techniques. Samples were provided by Drs. A.T. Anderson and D. Harris, W.B. Bryan, H. Craig, J.R. Delaney, D. Muenow, S. Newman, J.G. Schilling, and S.K. Sharma. The comments of Professors John Holloway, Harmon Craig, and Art Boettcher and of an anonymous reviewer are appreciated. Supported by NSF grants EAR-8212765 and EAR-8417434. Caltech Division of Geological and Planetary Sciences Contribution Number 4214.

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