Exercise: Loss time

Imagine a mica grain with a thickness of 200 µm, and a diffusivity for argon of 0.6 x 10^-18 cm²/s. How long, in Ma, will it take for this grain, assuming a plane sheet geometry, to loose ~50% of its argon (note the green lines in the diagram)?

Additional information: Take care of the units! You have to recalculate the time from seconds to million years, and the thickness from µm to cm. In this context, 1 year (a) = 365.25 days. Also note that the maximal diffusion distance is only half the thickness.

Provide the answer as a PDF. Not only provide the result, but also the way you did the calculation!

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