An experimental study of the diffusion of oxygen in quartz and albite using an overgrowth technique |
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| Authors: | S. C. Elphick P. F. Dennis C. M. Graham |
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| Affiliation: | (1) Department of Geology, Edinburgh University, West Mains Road, EH9 3JW Edinburgh, UK;(2) Department of Geology, Imperial College of Science and Technology, Prince Consort Road, SW7 2BP London, UK;(3) Present address: Department of Geological Sciences, University College, WC1 London, UK |
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| Abstract: | Diffusion rates of18O tracer in quartz ( c, 1 Kb H2O) and Amelia albite ( 001, 2 Kb H2O) have been measured, using Secondary Ion Mass Spectrometry (SIMS). A new technique involving hydrothermal deposition of labelled materials has removed the possibility of pressure solution-reprecipitation processes adversely affecting the experiments. Reported diffusion constants are: -quartz ( c), ,Q=98±7 KJ mol–1 (600–825° C, 1 Kb); Amelia albite ( 001), ,Q=85±7 KJ mol–1, (400–600° C, 2 Kb). Measured quartz18O diffusivities decrease discontinuously at the - transition, reflecting strong structural influences. The reported albite data agree with previously recorded studies, but-quartz data indicate significantly lower activation energies. Possible causes of this discrepancy, and some geological consequences, are noted. |
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