Diffusion in Geology
The U.S. government has sponsored a project which attempts to measure the diffusion coefficients of various cations in minerals which are present in the earth's crust. Since, at the temperatures actually present in the crust (especially the outer portions), diffusion is painfully slow, most experiments to this effect have been conducted at elevated temperature. Since diffusion coefficients depend greatly on temperature, these data have been criticized. Now, a technique using thin films and cation microprobes has been developed to measure diffusion coefficients at more realistic temperatures.
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