Interdiffusion of H2O and CO2 in metamorphic fluids at ∼490 to 690°C and 1 GPa

作者: David A. Wark , E.Bruce Watson

DOI: 10.1016/J.GCA.2003.12.006

关键词: FluxWollastoniteMineralogyCarbonateMass transferMetamorphic rockQuartzGeologyCalciteThermodynamicsThermal conduction

摘要: Interdiffusion coefficients have been determined for H 2O-CO2 mixtures by quantifying the flux of CO2 between two fluid-filled chambers in a specially designed piston-cylinder cell. The chambers, which are maintained at 1.0 GPa and temperatures differing 100°C, each contain XCO2-buffering assemblage calcite quartz wollastonite, H2O. positive dependence XCO2 on temperature results down-temperature, steady-state CO 2 through capillary tube that connects chambers. This drives wollastonite equilibrium to right cooler chamber, producing measurable amount is directly related CO2-H2O interdiffusion rates. Diffusivities calculated from seven experiments range 10 8 6.1 m /s mean 490 690°C. data set can be approximated an Arrhenius-type relation: D 4.7 -6 exp-4560/T (T K), yields values within factor of, but slightly lower than, diffusivities estimated application Stokes-Einstein relation. Because rates H2O approach (within 1 orders magnitude) heat conduction rocks, rapid should expected deep-seated fluids wherever gradients imposed contrasting mineral assemblages. Considering small-scale heterogeneity crust, strong probably quite common, particularly where different carbonate- bearing assemblages juxtaposed or they interlayered with carbonate-absent rocks. Cross-layer, diffusive mass transfer may play important role driving dehydration decarbonation reactions, even absence fluid flow. Copyright © 2004 Elsevier Ltd

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