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Carbonate ions in high-SiO2 rhyolite observed in fluid-melt equilibrium experiments

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Title: Carbonate ions in high-SiO2 rhyolite observed in fluid-melt equilibrium experiments
Authors: YOSHIMURA, SHUMPEI Browse this author →KAKEN DB
NAKAMURA, MICHIHIKO Browse this author
Keywords: rhyolite
Issue Date: 22-Mar-2017
Publisher: Geochemical Society of Japan
Journal Title: Geochemical Journal
Volume: 51
Issue: 3
Start Page: 251
End Page: 262
Publisher DOI: 10.2343/geochemj.2.0466
Abstract: We carried out equilibrium experiments of the CO2-H2O-rhyolite system at 0.1–1.5 GPa and 850 and 1200∞C to examine the solubility and speciation of CO2 in high-SiO2 rhyolite (SiO2 > 76 wt%). We observed that both CO2 molecules (CO2mol) and carbonate anions (CO3 2–) are dissolved in the quenched rhyolitic glasses based on infrared spectroscopy. This result contrasts with the general understanding that high-SiO2 rhyolitic melt dissolves CO2mol only. The concentrations of CO2mol and CO3 2– were 199–9200 ppm and 58–2100 ppm, respectively, as quantified based on the Beer-Lambert’s law and newly determined extinction coefficients of 1192 ± 130 L·cm–1·mol–1 and 91 ± 28 L·cm–1·mol–1 for CO2mol and CO3 2–, respectively. The water content ranged from 2.6 to 6.1 wt%. Using the thermodynamic analysis, we calculated the partial molar volume of CO2mol to be VCO mol melt 2 = 24.9 ± 2.0 cm3/mol and enthalpy of dissolution to be DslnH = –22.2 ± 6.3 kJ/mol. Changes in volume and enthalpy upon the formation reaction of CO3 2– were calculated to be DrV = –8.6 ± 0.9 cm3/ mol and DrH = +1.1 ± 4.4 kJ/mol, respectively.
Type: article
Appears in Collections:理学院・理学研究院 (Graduate School of Science / Faculty of Science) > 雑誌発表論文等 (Peer-reviewed Journal Articles, etc)

Submitter: 吉村 俊平

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