Pore microstructure in fluid-bearing rocks of the deep crust is controlled largely by the ratio of grain-boundary energy (γ_(gb)) to the interfacial energy of the pore wall (γ_(cf)). With the goal of better characterizing pore topology in equilibrated rocks, we have developed a technique to quantify γ_(gb)/γ_(cf) for different degrees of lattice "misfit" at a grain boundary. We first juxtapose two oriented crystal surfaces in the presence of fluid at elevated pressure and temperature. Lenticular-shaped pores that form along that surface are then characterized by atomic force microscopy to allow quantitative measurement of wetting properties, from which the ratio γ_(gb)/γ_(cf) can be extracted. Initial results show promise not only for quantifying grain-boundary energies, but also for understanding the influence of crystal lattice orientation on the shape of pore walls.
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