Details
| Original language | English |
|---|---|
| Pages (from-to) | 327-340 |
| Number of pages | 14 |
| Journal | Chemical geology |
| Volume | 209 |
| Issue number | 3-4 |
| Publication status | Published - 27 Sept 2004 |
Abstract
We report the first experimental study of the diffusion of H2O in dacitic melts. Dehydration experiments were conducted at 551-637 °C and 1-1450 bars for samples with ∼0.8 to ∼2.5 wt.% total dissolved H2O. The H2O diffusivity is proportional to total H2O contents at ≤0.8 wt.%, but increases exponentially with total H2O at higher H2O contents. The diffusivity of the total dissolved H2O (in μm2/s) can be modeled as DH2Ot = Xexp[20.463 - 40.433X + (- 18, 106 + 69, 230X)/T], where X is the mole fraction of the total dissolved H2O on a single oxygen basis and T is in Kelvin. In the investigated T-range, H2O diffuses more slowly in hydrous dacitic melt than in rhyolitic melt, by a factor of 2 to 12. When compared to H2O diffusion in rhyolite, the activation energy in dacite is greater (124-142 vs. 87-91 kJ/mol). Therefore, extrapolation of DH2Ot in dacite to higher T suggests that above certain T, H2O diffusivity in dacite would be greater than that in rhyolite (e.g., at >740 °C and 100 MPa for a total H2O content of 2.5 wt.%).
Keywords
- Bubble growth, Dacitic melt, Magma fragmentation, Water diffusion
ASJC Scopus subject areas
- Earth and Planetary Sciences(all)
- Geology
- Earth and Planetary Sciences(all)
- Geochemistry and Petrology
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In: Chemical geology, Vol. 209, No. 3-4, 27.09.2004, p. 327-340.
Research output: Contribution to journal › Article › Research › peer review
}
TY - JOUR
T1 - H2O diffusion in dacitic melts
AU - Liu, Yang
AU - Zhang, Youxue
AU - Behrens, Harald
N1 - Funding Information: This work was supported by US NSF grants INT-9815351, EAR-9972937, EAR-0106718 and EAR-0125506 and by the DFG grants Ho1337/3 and Ho1337/7. We thank Susanne Ohlhorst for providing anhydrous dacitic samples, Melanie Sierralta and Astrid Tegge-Schüring for helping with the internally heated pressure vessel, Hejiu Hui for sharing unpublished data for quench rate of CSV-2, and Otto Diedrich for preparation of some doubly polished samples and microprobe samples. We also thank James Mungall, Alan Whittington and Sumit Chakraborty for their thorough and constructive reviews. [RR]
PY - 2004/9/27
Y1 - 2004/9/27
N2 - We report the first experimental study of the diffusion of H2O in dacitic melts. Dehydration experiments were conducted at 551-637 °C and 1-1450 bars for samples with ∼0.8 to ∼2.5 wt.% total dissolved H2O. The H2O diffusivity is proportional to total H2O contents at ≤0.8 wt.%, but increases exponentially with total H2O at higher H2O contents. The diffusivity of the total dissolved H2O (in μm2/s) can be modeled as DH2Ot = Xexp[20.463 - 40.433X + (- 18, 106 + 69, 230X)/T], where X is the mole fraction of the total dissolved H2O on a single oxygen basis and T is in Kelvin. In the investigated T-range, H2O diffuses more slowly in hydrous dacitic melt than in rhyolitic melt, by a factor of 2 to 12. When compared to H2O diffusion in rhyolite, the activation energy in dacite is greater (124-142 vs. 87-91 kJ/mol). Therefore, extrapolation of DH2Ot in dacite to higher T suggests that above certain T, H2O diffusivity in dacite would be greater than that in rhyolite (e.g., at >740 °C and 100 MPa for a total H2O content of 2.5 wt.%).
AB - We report the first experimental study of the diffusion of H2O in dacitic melts. Dehydration experiments were conducted at 551-637 °C and 1-1450 bars for samples with ∼0.8 to ∼2.5 wt.% total dissolved H2O. The H2O diffusivity is proportional to total H2O contents at ≤0.8 wt.%, but increases exponentially with total H2O at higher H2O contents. The diffusivity of the total dissolved H2O (in μm2/s) can be modeled as DH2Ot = Xexp[20.463 - 40.433X + (- 18, 106 + 69, 230X)/T], where X is the mole fraction of the total dissolved H2O on a single oxygen basis and T is in Kelvin. In the investigated T-range, H2O diffuses more slowly in hydrous dacitic melt than in rhyolitic melt, by a factor of 2 to 12. When compared to H2O diffusion in rhyolite, the activation energy in dacite is greater (124-142 vs. 87-91 kJ/mol). Therefore, extrapolation of DH2Ot in dacite to higher T suggests that above certain T, H2O diffusivity in dacite would be greater than that in rhyolite (e.g., at >740 °C and 100 MPa for a total H2O content of 2.5 wt.%).
KW - Bubble growth
KW - Dacitic melt
KW - Magma fragmentation
KW - Water diffusion
UR - http://www.scopus.com/inward/record.url?scp=11044232616&partnerID=8YFLogxK
U2 - 10.1016/j.chemgeo.2004.06.019
DO - 10.1016/j.chemgeo.2004.06.019
M3 - Article
AN - SCOPUS:11044232616
VL - 209
SP - 327
EP - 340
JO - Chemical geology
JF - Chemical geology
SN - 0009-2541
IS - 3-4
ER -