HR: 11:20h
AN: V51L-05    [PDF]
TI: Solubility of H$_{2}$O in Rhyolitic Melts at Low Pressures
AU: * Liu, Y
EM: yangl@geosci.uchicago.edu
AF: University of Michigan, Department of Geological Sciences, Ann Arbor, MI 48109-1063 United States
AU: Zhang, Y
EM: youxue@umich.edu
AF: University of Michigan, Department of Geological Sciences, Ann Arbor, MI 48109-1063 United States
AU: Behrens, H
EM: H.Behrens@mineralogie.uni-hannover.de
AF: Universit$\ddot{a}$t Hannover, Institut f$\ddot{u}$r Mineralogie, Callinstr. 3, Hannover, D-30167 Germany
AB: Reversal experiments of H$_{2}$O solubility in synthetic haplogranitic and natural rhyolitic melts were conducted at $700-1200\deg$C and 0.098-25 MPa. H$_{2}$O contents were determined using Fourier transform infrared spectroscopy. When temperature decreases from 1000 to $700\deg$C, the solubility of H$_{2}$O increases from 0.100 to 0.124 wt% at 0.098 MPa, from 0.99 to 1.36 wt% at 11 MPa, and from 1.46 to 2.17 wt% at 25 MPa. At 6 MPa, the solubility of H$_{2}$O increases from 0.63 to 0.77 wt% from 1200 to $850\deg$C. Using these data and those from the literature for a total of 203 measurements, an empirical solubility model for pure H$_{2}$O fluid has been constructed for rhyolitic melt and takes the following expression: w=(354.97P$_{w}^{0.5}$+9.585P$_{w}$-1.5095P$_{w}^{1.5}$)/T+0.0012365P$_{w}^{1.5}$, where w is water contents in wt%, P$_{w}$=X$_{w}^{f}$P (in MPa) where X$_{w}^{f}$ is the mole fraction of H$_{2}$O in the fluid, and T is in K. This empirical model has a 2$\sigma$ relative uncertainty of 10% and is applicable to $700-1200\deg$C and 0-500 MPa. It also applies to H$_{2}$O solubility in mixed H$_{2}$O-H$_{2}$ fluid at total pressure $\leq$300 MPa (that is, the presence of H$_{2}$ in the fluid does not affect H$_{2}$O solubility). An empirical model for mixed H$_{2}$O-CO$_{2}$ solubility is developed and consists two equations: w=(354.97P$_{w}^{0.5}$+9.585P$_{w}$-1.5095P$_{w}^{1.5}$)/T+0.0012365P$_{w}$$^{1.5}$+P$_{CO2}$(-0.0001102P$_{w}^{0.5}$-1.341$\ times$10$^{-5}$P$_{w}$), CO$_{2}$=(7507P$_{CO2}$-1.86P$_{CO2}^{2}$)/T+0.905P$_{w}^{0.5}$P$_{CO2}$+ P$_{CO2}$(-785.3P$_{w}^{0.5}$-40.85P$_{w}$+2.291P$_{w}^{1.5}$)/T, where w is water content in wt%, CO$_{2}$ content is in ppm by mass, P$_{w}$=X$_{w}^{f}$P and P$_{CO2}$=X$_{CO2}^{f}$P (in MPa), where X$_{w}^{f}$ and X$_{CO2}^{f}$ are the mole fraction of H$_{2}$O and CO$_{2}$ in the fluid, and T is in K. The above equations are applicable to $700-1200\deg$C and total pressure of $\leq$500 MPa. The 2$\sigma$ relative uncertainty is 13% for the H$_{2}$O equation, and 25% for the CO$_{2}$ equation. Both empirical models are recommended for the modeling of volcanic eruptions and magma chamber dynamics.
DE: 1000 GEOCHEMISTRY (New field, replaces Rock Chemistry)
DE: 3630 Experimental mineralogy and petrology
DE: 8400 VOLCANOLOGY
DE: 8414 Eruption mechanisms
DE: 8439 Physics and chemistry of magma bodies
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2003 Fall Meeting