Diffusional transport and fluid connectivity in mineral aggregates. Final report [for the period August 15, 1994 to August 15, 1999]
Description: The objectives of this study were to determine diffusional transport rates of oxygen and selected geologically and environmentally important cations in polycrystalline mineral aggregates. The samples included both natural and hot-pressed single and polyphase aggregates of common mineralogies. In addition to determining grain boundary diffusion rates in these samples, bulk diffusivity measurements were made to evaluate the connectivity of common geological fluids as a function of temperature, pressure, fluid composition and volume fraction, mineralogy (anisotropy of interfacial energies), and stress state in the solid. An integral part of these investigations was the detailed characterization of the sample microstructures using SEM and TEM in order to evaluate whether a correlation between microstructure observations and bulk diffusional transport distances can be established, thus providing a valuable tool for predicting diffusional transport and fluid connectivity in natural samples. Applications of these data include evaluating the retentiveness of different geological medium for the isolation and confinement of nuclear and chemical wastes, modeling the migration of formation fluids and hydrocarbons through different rock types to refine exploration and development strategies for more efficient oil and natural gas recovery, and determining fluid/rock interactions and thermal histories from isotope systematics which, among other things, provide models for modern-day geothermal/hydrothermal energy systems and ore-body deposition associated with fossil hydrothermal systems.
Date: August 12, 1999
Creator: Yund, Richard & Farver, John
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