Details
| Originalsprache | Englisch |
|---|---|
| Seiten (von - bis) | 363-376 |
| Seitenumfang | 14 |
| Fachzeitschrift | Earth and Planetary Science Letters |
| Jahrgang | 192 |
| Ausgabenummer | 3 |
| Frühes Online-Datum | 22 Okt. 2001 |
| Publikationsstatus | Veröffentlicht - 30 Okt. 2001 |
Abstract
The effect of dissolved water on the diffusivity of Ar in glasses and melts of rhyolitic and albitic compositions was investigated experimentally at pressures up to 1500 MPa and water contents of 0.1-5 wt%. The data for water-poor rhyolitic composition at 500 MPa can be described in the whole temperature range of 480-1102°C by a simple Arrhenius relationship DAr = 2.14 × 10-6 m2/s exp(-18 883/T). A 4.0 wt% increase in water content increases the Ar diffusivity by approximately one order of magnitude in both rhyolitic and albitic melts at 1000°C. In contrast to viscosity and total water diffusion, an exponential dependence of Ar diffusivity on water content was observed for the rhyolitic composition in the whole range of water contents. For water-poor rhyolite, Ar diffusivity depends on pressure with an apparent activation volume of 13-15 cm3/mol at pressures up to 800 MPa. For water-rich rhyolite ( ~ 5 wt% water), there is no significant pressure effect at 1000°C in the range 500-1500 MPa. Combining our data with previous data from Carroll [M.R. Carroll, Earth Planet. Sci. Lett. 103 (1991) 156-168], Ar diffusivity (in 10-12 m2/s) in rhyolitic melts can be expressed as:. DAr = exp[(14.627-17913/T-2.569P/T) + (35936/T + 27.42P/T)Xwater], where T is in K, P in MPa, and Xwater is the mol fraction of water on a single oxygen basis. Except for two outlier points, error of estimates is ≤ 0.455 in terms of In D for all data, covering a wide range of temperatures (480-1200°C), pressures (0.1-1500 MPa), and water contents (0.1-5 wt%). The new Ar diffusion data support the assumption that molecular H2O diffusivity exponentially increases with water content [Y. Zhang, H. Behrens, Chem. Geol. 169 (2000) 243-262].
ASJC Scopus Sachgebiete
- Erdkunde und Planetologie (insg.)
- Geophysik
- Erdkunde und Planetologie (insg.)
- Geochemie und Petrologie
- Erdkunde und Planetologie (insg.)
- Erdkunde und Planetologie (sonstige)
- Erdkunde und Planetologie (insg.)
- Astronomie und Planetologie
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in: Earth and Planetary Science Letters, Jahrgang 192, Nr. 3, 30.10.2001, S. 363-376.
Publikation: Beitrag in Fachzeitschrift › Artikel › Forschung › Peer-Review
}
TY - JOUR
T1 - Ar diffusion in hydrous silicic melts
T2 - Implications for volatile diffusion mechanisms and fractionation
AU - Behrens, Harald
AU - Zhang, Youxue
N1 - Funding Information: This research is supported by NSF Grants INT-9815351 and EAR-9972937 and by the German DAAD. We thank S. Chakraborty, D. Draper and an anonymous third reviewer for their constructive and insightful comments. [BW]
PY - 2001/10/30
Y1 - 2001/10/30
N2 - The effect of dissolved water on the diffusivity of Ar in glasses and melts of rhyolitic and albitic compositions was investigated experimentally at pressures up to 1500 MPa and water contents of 0.1-5 wt%. The data for water-poor rhyolitic composition at 500 MPa can be described in the whole temperature range of 480-1102°C by a simple Arrhenius relationship DAr = 2.14 × 10-6 m2/s exp(-18 883/T). A 4.0 wt% increase in water content increases the Ar diffusivity by approximately one order of magnitude in both rhyolitic and albitic melts at 1000°C. In contrast to viscosity and total water diffusion, an exponential dependence of Ar diffusivity on water content was observed for the rhyolitic composition in the whole range of water contents. For water-poor rhyolite, Ar diffusivity depends on pressure with an apparent activation volume of 13-15 cm3/mol at pressures up to 800 MPa. For water-rich rhyolite ( ~ 5 wt% water), there is no significant pressure effect at 1000°C in the range 500-1500 MPa. Combining our data with previous data from Carroll [M.R. Carroll, Earth Planet. Sci. Lett. 103 (1991) 156-168], Ar diffusivity (in 10-12 m2/s) in rhyolitic melts can be expressed as:. DAr = exp[(14.627-17913/T-2.569P/T) + (35936/T + 27.42P/T)Xwater], where T is in K, P in MPa, and Xwater is the mol fraction of water on a single oxygen basis. Except for two outlier points, error of estimates is ≤ 0.455 in terms of In D for all data, covering a wide range of temperatures (480-1200°C), pressures (0.1-1500 MPa), and water contents (0.1-5 wt%). The new Ar diffusion data support the assumption that molecular H2O diffusivity exponentially increases with water content [Y. Zhang, H. Behrens, Chem. Geol. 169 (2000) 243-262].
AB - The effect of dissolved water on the diffusivity of Ar in glasses and melts of rhyolitic and albitic compositions was investigated experimentally at pressures up to 1500 MPa and water contents of 0.1-5 wt%. The data for water-poor rhyolitic composition at 500 MPa can be described in the whole temperature range of 480-1102°C by a simple Arrhenius relationship DAr = 2.14 × 10-6 m2/s exp(-18 883/T). A 4.0 wt% increase in water content increases the Ar diffusivity by approximately one order of magnitude in both rhyolitic and albitic melts at 1000°C. In contrast to viscosity and total water diffusion, an exponential dependence of Ar diffusivity on water content was observed for the rhyolitic composition in the whole range of water contents. For water-poor rhyolite, Ar diffusivity depends on pressure with an apparent activation volume of 13-15 cm3/mol at pressures up to 800 MPa. For water-rich rhyolite ( ~ 5 wt% water), there is no significant pressure effect at 1000°C in the range 500-1500 MPa. Combining our data with previous data from Carroll [M.R. Carroll, Earth Planet. Sci. Lett. 103 (1991) 156-168], Ar diffusivity (in 10-12 m2/s) in rhyolitic melts can be expressed as:. DAr = exp[(14.627-17913/T-2.569P/T) + (35936/T + 27.42P/T)Xwater], where T is in K, P in MPa, and Xwater is the mol fraction of water on a single oxygen basis. Except for two outlier points, error of estimates is ≤ 0.455 in terms of In D for all data, covering a wide range of temperatures (480-1200°C), pressures (0.1-1500 MPa), and water contents (0.1-5 wt%). The new Ar diffusion data support the assumption that molecular H2O diffusivity exponentially increases with water content [Y. Zhang, H. Behrens, Chem. Geol. 169 (2000) 243-262].
KW - Albite
KW - Argon diffusion
KW - Degassing
KW - Glasses
KW - Melts
KW - Rhyolites
UR - http://www.scopus.com/inward/record.url?scp=0035169202&partnerID=8YFLogxK
U2 - 10.1016/S0012-821X(01)00458-7
DO - 10.1016/S0012-821X(01)00458-7
M3 - Article
AN - SCOPUS:0035169202
VL - 192
SP - 363
EP - 376
JO - Earth and Planetary Science Letters
JF - Earth and Planetary Science Letters
SN - 0012-821X
IS - 3
ER -