The upper three-phase region in the system SiO 2 -H 2 O

Kennedy, George C.; Wasserburg, G. J.; Heard, H.C.; Newton, Robert C.

doi:10.2475/ajs.260.7.501

Cited by 278 publications

(122 citation statements)

References 0 publications

Supporting

Mentioning

110

Contrasting

Unclassified

Order By: Relevance

“…In this context it is interesting to note that problems of solution-reprecipitation were anticipated with the quartz experiments because of the relatively high solubility of SiO2 in H20 at 600-700 ~ at 1 kbar (Walther and Helgeson, 1977). Since the diffusion profiles showed little or no evidence of such problems, it would appear that the faster dissolution of the sawn cut-back surfaces of the specimen buffered the system and preserved the finish on the (more stable) polished faces (Vig et al, 1977;Suda et al, 1978;Kennedy et al, 1962). It is concluded, that in order to avoid the generation of artificially high diffusion coefficients, the specimens should be prepared to minimize the defect concentrations and sample damage, and the experiments should be performed under conditions where the specimen is stable (Giletti, 1974a).…”

Section: Experimental Considerationsmentioning

confidence: 99%

Oxygen diffusion studies. I. A preliminary ion microprobe investigation of oxygen diffusion in some rock-forming minerals

Freer

Dennis

1982

Mineral. mag.

View full text Add to dashboard Cite

The self diffusion of oxygen has been studied in prepared natural crystals of albite, grossular garnet, quartz, and ruffle by isotope exchange with hydrothermal water enriched in 18O, and subsequent analysis by ion microprobe. Measured oxygen diffusion coefficients (D) in quartz (‖c) may be described by D = 1.08 × 10−11 exp(−31.5 kcal/RT) cm2s−1 at 600−750°C and 1 kbar water pressure. For grossular, D = 2.5 × 10−16 cm2s−1 at 1050°C and 8 kbar, and D = 4.8 × 10−17 cm2s−1 at 850 °C and 2 kbar. All ruffle crystals exhibited variable amounts of corrosion, and an approximate diffusion coefficient of D(‖c) = 3.16 × 10−15 cm2s−1 cm2s−1 was obtained at 1050 °C and 1 kbar. Oxygen diffusion coefficients in albite, perpendicular to (001) faces, have been determined as a function of pressure at 600 °C Between 0.5 and 8.0 kbar pressure no systematic variation in the results was observed and most of the data may be described by D = 4.1 (±0.5) × 10−15 cm2s−1. Slow oxygen diffusion rates in quartz and garnet suggest that these minerals should have high ‘closure temperatures’ for oxygen exchange, and may provide reliable oxygen isotope exchange geothermometers.

show abstract

Section: Experimental Considerationsmentioning

confidence: 99%

Oxygen diffusion studies. I. A preliminary ion microprobe investigation of oxygen diffusion in some rock-forming minerals

Freer

Dennis

1982

Mineral. mag.

View full text Add to dashboard Cite

show abstract

“…In addition, there are also arguments showing that the melt composition has a significant effect on the amount of water dissolved as OH groups. For example, H20 solubility data for Qz, Ab, Or and Qz-Ab melts (Kennedy et al, 1962;Oxtoby and Hamilton, 1978a, b;see review in McMillan and Holloway, 1987) indicate that the difference in H20 solubility between melts of different compositions strongly increases with increasing pressure from 0 to 2 kbar (i.e. at low H20 contents and thus for high proportions of OH groups) whereas this difference remains almost constant for pressures between 2 and 10 kbar (i.e.…”

Section: Importance For H20 Solubility Mechanisms In Aluminosilicate mentioning

confidence: 99%

Water solubility in aluminosilicate melts of haplogranite composition at 2 kbar

et al. 1992

View full text Add to dashboard Cite

The compositional dependence of H20 solubility was investigated at 2 kbar and 800 °C in haplogranite melts (system SiO2-NaAISi3Os-KA1Si308 or Qz-Ab-Or). The sixteen investigated compositions contained 25, 35 or 45 wt.% normative Qz and various Ab/(Ab + Or ) ratios (0.15-0.92 ). Starting solid materials were anhydrous bubble-free glasses to which 10 wt.% H20 was added. The H20 contents of the isobarically quenched melts (glasses) were measured by Karl-Fischer titration.The results show that H20 solubility in aluminosilicate melts depends significantly upon anhydrous composition. The highest solubility values are obtained for the most Ab-rich melts. At a constant normative quartz content, the solubility of water decreases from 6.49 _+ 0.20 wt.% H20 for a composition Qz35AbroOro5 (normative composition expressed in wt.%) to 5.50 4-_ 0.15 wt.% H20 for a composition QzasAbloOr55. Along this join, the most significant changes are observed for Ab-rich melts whereas H20 solubility in Or-rich melts remains almost constant.The H20 solubility data imply that H20 is preferentially associated with the Ab component in aluminosilicate melts.Application of the results to natural granitic melts suggests that Na-rich, H20-saturated melts may be significantly less viscous than H20-saturated, K-rich melts.The temperature dependence of H20 solubility, investigated for composition Qz28Ab38Or34 at 2 kbar, is low. Increasing temperature from 750 ° to 1150 °C only causes a decrease in H20 solubility from 6.00 to 5.41 wt.% H20. These data are in agreement with previous data obtained for albite melts.

show abstract

“…For example, water was shown to decrease melting temperatures [2,10,11] and viscosities [12], to increase devitrification rates [13] and to affect optical properties of vitreous silica [14,15]. Therefore, the dissolution mechanisms of water have been the object of various studies using vibrational spectroscopic techniques such as Raman and infrared (IR) spectroscopy (see [16,17] for recent reviews).…”

Section: Introductionmentioning

confidence: 99%

“…The incorporation of volatiles such as noble gases, carbon dioxide and water in silica glasses and melts has been widely investigated [2,3,4,5,6,7,8] with respect to physical properties affected by the presence of the volatiles and their related species in the silicate network (see [9] for a recent review of microscopic models for water dissolution). For example, water was shown to decrease melting temperatures [2,10,11] and viscosities [12], to increase devitrification rates [13] and to affect optical properties of vitreous silica [14,15].…”

Section: Introductionmentioning

confidence: 99%

Incorporation of H2 in vitreous silica, qualitative and quantitative determination from Raman and infrared spectroscopy

Schmidt

Holtz

Bény

1998

Journal of Non-Crystalline Solids

View full text Add to dashboard Cite

Incorporation mechanisms of H 2 in silica glass were studied with Raman and infrared (IR) microspectroscopy. Hydrogenated samples were prepared at temperatures between 800°C and 955°C at 2 kbar total pressure. Hydrogen fugacities (f H2 ) were controlled using the double capsule technique with the iron-wüstite (IW) buffer assemblage generating f H2 of 1290-1370 bars corresponding to H 2 partial pressures (P H2 ) of 960-975 bars. We found that silica glass hydrogenated under such conditions contains molecular hydrogen (H 2 ) in addition to SiH and SiOH groups. H 2 molecules dissolved in the quenched glasses introduce a band at 4136 cmin the Raman spectra which in comparison to that of gaseous H 2 is wider and is shifted to lower frequency. IR spectra of hydrogenated samples contain a band at 4138 cm −1 which we assign to the stretching vibration of H 2 molecules located in non-centrosymmetric sites. The Raman and IR spectra indicate that the dissolved H 2 molecules interact with the silicate network. We suggest that the H 2 band is the envelope of at least three components due to the occupation of at least three different interstitial sites by H 2 molecules. Both, Raman and IR spectra of hydrogenated glasses contain bands at 2255 cm −1 which may be due to the vibration of SiH groups. Under the assumption that the reaction Si-O-Si + H 2 → Si-H + Si-O-H describes adequately the 'chemical dissolution' of H 2 molecules, the SiH concentrations in our samples were determined and the molar extinction coefficient for the SiH absorption band in the infrared ( 2255 (SiH)) could then be estimated to be 45 ± 3 l/mol cm. The solubility of molecular H 2 in our hydrogenated samples was determined using the IR absorption band at 4138 cm −1 and the extinction coefficient given by Shelby [J. Non-Cryst. Solids 179 (1994) 138]. Samples quenched with different cooling rates gave nearly identical Raman and IR spectra, suggesting that the chemical dissolution of hydrogen (SiH and SiOH) can be quenched to room temperature without changing relative concentrations and that no exsolution of hydrogen occurred during the quench.

show abstract

The upper three-phase region in the system SiO 2 -H 2 O

Cited by 278 publications

References 0 publications

Oxygen diffusion studies. I. A preliminary ion microprobe investigation of oxygen diffusion in some rock-forming minerals

Oxygen diffusion studies. I. A preliminary ion microprobe investigation of oxygen diffusion in some rock-forming minerals

Water solubility in aluminosilicate melts of haplogranite composition at 2 kbar

Incorporation of H2 in vitreous silica, qualitative and quantitative determination from Raman and infrared spectroscopy

Contact Info

Product

Resources

About