Ar diffusion in hydrous silicic melts: implications for volatile diffusion mechanisms and fractionation

Computer Science

Scientific paper

Rate now

  [ 0.00 ] – not rated yet Voters 0   Comments 0

Details

12

Scientific paper

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(-18883/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 ln 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].

No associations

LandOfFree

Say what you really think

Search LandOfFree.com for scientists and scientific papers. Rate them and share your experience with other people.

Rating

Ar diffusion in hydrous silicic melts: implications for volatile diffusion mechanisms and fractionation does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.

If you have personal experience with Ar diffusion in hydrous silicic melts: implications for volatile diffusion mechanisms and fractionation, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Ar diffusion in hydrous silicic melts: implications for volatile diffusion mechanisms and fractionation will most certainly appreciate the feedback.

Rate now

     

Profile ID: LFWR-SCP-O-1104989

  Search
All data on this website is collected from public sources. Our data reflects the most accurate information available at the time of publication.