Details
| Originalsprache | Englisch |
|---|---|
| Seiten (von - bis) | 3642-3655 |
| Seitenumfang | 14 |
| Fachzeitschrift | Geochimica et cosmochimica acta |
| Jahrgang | 73 |
| Ausgabenummer | 12 |
| Frühes Online-Datum | 2 Apr. 2009 |
| Publikationsstatus | Veröffentlicht - 15 Juni 2009 |
Abstract
H2O diffusion in dacitic melt was investigated at 0.48-0.95 GPa and 786-893 K in a piston-cylinder apparatus. The diffusion couple design was used, in which a nominally dry dacitic glass makes one half and is juxtaposed with a hydrous dacitic glass containing up to ∼8 wt.% total water (H2Ot). H2O concentration profiles were measured on quenched glasses with infrared microspectroscopy. The H2O diffusivity in dacite increases rapidly with water content under experimental conditions, similar to previous measurements at the same temperature but at pressure <0.15 GPa. However, compared with the low-pressure data, H2O diffusion at high pressure is systematically slower. H2O diffusion profiles in dacite can be modeled by assuming molecular H2O (H2Om) is the diffusing species. Total H2O diffusivity DH2 Ot within 786-1798 K, 0-1 GPa, and 0-8 wt.% H2Ot can be expressed as: DH2 Ot = fenced(1 + frac(2 X - 1, sqrt(4 X (X - 1) (1 - 4 / K) + 1))) exp fenced(- 9.423 - 62.38 X - frac(19064 - 108882 X + 1476.7 P, T)), where DH2 Ot is in m2/s, T is temperature in K, P is pressure in GPa, K = exp(1.49 - 2634/T) is the equilibrium constant of speciation reaction (H2 Om + O ⇌ 2 OH) in the melt, X = C/18.015/[C/18.015 + (100 - C)/33.82], C is wt.% of H2Ot, and 18.015 and 33.82 g/mol correspond to the molar masses of H2O and anhydrous dacite on a single oxygen basis. Compared to H2O diffusion in rhyolite, diffusivity in dacite is lower at intermediate temperatures but higher at superliquidus temperatures. This general H2O diffusivity expression can be applied to a broad range of geological conditions, including both magma chamber processes and volcanic eruption dynamics from conduit to the surface.
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- Erdkunde und Planetologie (insg.)
- Geochemie und Petrologie
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in: Geochimica et cosmochimica acta, Jahrgang 73, Nr. 12, 15.06.2009, S. 3642-3655.
Publikation: Beitrag in Fachzeitschrift › Artikel › Forschung › Peer-Review
}
TY - JOUR
T1 - Water diffusion in dacitic melt
AU - Ni, Huaiwei
AU - Behrens, Harald
AU - Zhang, Youxue
N1 - Funding Information: We are grateful to Hejiu Hui and Yang Liu for synthesizing the dacitic glasses, Satoshi Okumura for providing the original dehydration data, Yang Chen for electron microprobe analysis, Eric Essene, Rebecca Lange, Zhan Chen, Sam Mukasa, and Haoyue Wang for discussion. Constructive reviews from Yan Liang, Oded Navon, and Alan Whittington significantly improved the manuscript. This work is supported by grants from NSF (EAR-0537598 and EAR-0711050).
PY - 2009/6/15
Y1 - 2009/6/15
N2 - H2O diffusion in dacitic melt was investigated at 0.48-0.95 GPa and 786-893 K in a piston-cylinder apparatus. The diffusion couple design was used, in which a nominally dry dacitic glass makes one half and is juxtaposed with a hydrous dacitic glass containing up to ∼8 wt.% total water (H2Ot). H2O concentration profiles were measured on quenched glasses with infrared microspectroscopy. The H2O diffusivity in dacite increases rapidly with water content under experimental conditions, similar to previous measurements at the same temperature but at pressure <0.15 GPa. However, compared with the low-pressure data, H2O diffusion at high pressure is systematically slower. H2O diffusion profiles in dacite can be modeled by assuming molecular H2O (H2Om) is the diffusing species. Total H2O diffusivity DH2 Ot within 786-1798 K, 0-1 GPa, and 0-8 wt.% H2Ot can be expressed as: DH2 Ot = fenced(1 + frac(2 X - 1, sqrt(4 X (X - 1) (1 - 4 / K) + 1))) exp fenced(- 9.423 - 62.38 X - frac(19064 - 108882 X + 1476.7 P, T)), where DH2 Ot is in m2/s, T is temperature in K, P is pressure in GPa, K = exp(1.49 - 2634/T) is the equilibrium constant of speciation reaction (H2 Om + O ⇌ 2 OH) in the melt, X = C/18.015/[C/18.015 + (100 - C)/33.82], C is wt.% of H2Ot, and 18.015 and 33.82 g/mol correspond to the molar masses of H2O and anhydrous dacite on a single oxygen basis. Compared to H2O diffusion in rhyolite, diffusivity in dacite is lower at intermediate temperatures but higher at superliquidus temperatures. This general H2O diffusivity expression can be applied to a broad range of geological conditions, including both magma chamber processes and volcanic eruption dynamics from conduit to the surface.
AB - H2O diffusion in dacitic melt was investigated at 0.48-0.95 GPa and 786-893 K in a piston-cylinder apparatus. The diffusion couple design was used, in which a nominally dry dacitic glass makes one half and is juxtaposed with a hydrous dacitic glass containing up to ∼8 wt.% total water (H2Ot). H2O concentration profiles were measured on quenched glasses with infrared microspectroscopy. The H2O diffusivity in dacite increases rapidly with water content under experimental conditions, similar to previous measurements at the same temperature but at pressure <0.15 GPa. However, compared with the low-pressure data, H2O diffusion at high pressure is systematically slower. H2O diffusion profiles in dacite can be modeled by assuming molecular H2O (H2Om) is the diffusing species. Total H2O diffusivity DH2 Ot within 786-1798 K, 0-1 GPa, and 0-8 wt.% H2Ot can be expressed as: DH2 Ot = fenced(1 + frac(2 X - 1, sqrt(4 X (X - 1) (1 - 4 / K) + 1))) exp fenced(- 9.423 - 62.38 X - frac(19064 - 108882 X + 1476.7 P, T)), where DH2 Ot is in m2/s, T is temperature in K, P is pressure in GPa, K = exp(1.49 - 2634/T) is the equilibrium constant of speciation reaction (H2 Om + O ⇌ 2 OH) in the melt, X = C/18.015/[C/18.015 + (100 - C)/33.82], C is wt.% of H2Ot, and 18.015 and 33.82 g/mol correspond to the molar masses of H2O and anhydrous dacite on a single oxygen basis. Compared to H2O diffusion in rhyolite, diffusivity in dacite is lower at intermediate temperatures but higher at superliquidus temperatures. This general H2O diffusivity expression can be applied to a broad range of geological conditions, including both magma chamber processes and volcanic eruption dynamics from conduit to the surface.
UR - http://www.scopus.com/inward/record.url?scp=65549099391&partnerID=8YFLogxK
U2 - 10.1016/j.gca.2009.03.029
DO - 10.1016/j.gca.2009.03.029
M3 - Article
AN - SCOPUS:65549099391
VL - 73
SP - 3642
EP - 3655
JO - Geochimica et cosmochimica acta
JF - Geochimica et cosmochimica acta
SN - 0016-7037
IS - 12
ER -