H2O diffusion in dacitic melts

Yang Liu; Youxue Zhang; Harald Behrens

doi:10.1016/j.chemgeo.2004.06.019

H₂O diffusion in dacitic melts

Yang Liu^*, Youxue Zhang, Harald Behrens

^*Corresponding author for this work

Research output: Contribution to journal › Article › Research › peer review

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 D_H2Ot = 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 D_H2Ot 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.%).

Original language	English
Pages (from-to)	327-340
Number of pages	14
Journal	Chemical geology
Volume	209
Issue number	3-4
DOIs	https://doi.org/10.1016/j.chemgeo.2004.06.019
Publication status	Published - 27 Sept 2004

Keywords

Bubble growth
Dacitic melt
Magma fragmentation
Water diffusion

ASJC Scopus subject areas

Geology
Geochemistry and Petrology

Access to Document

10.1016/j.chemgeo.2004.06.019

Cite this

@article{16559f9514e14f6f8b56acb7bc66b547,

title = "H2O diffusion in dacitic melts",

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",

author = "Yang Liu and Youxue Zhang and Harald Behrens",

note = "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-Sch{\"u}ring 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]",

year = "2004",

month = sep,

day = "27",

doi = "10.1016/j.chemgeo.2004.06.019",

language = "English",

volume = "209",

pages = "327--340",

journal = "Chemical geology",

issn = "0009-2541",

publisher = "Elsevier BV",

number = "3-4",

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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

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U2 - 10.1016/j.chemgeo.2004.06.019

DO - 10.1016/j.chemgeo.2004.06.019

M3 - Article

AN - SCOPUS:11044232616

SN - 0009-2541

VL - 209

SP - 327

EP - 340

JO - Chemical geology

JF - Chemical geology

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