9316465 Bennett This project seeks to quantify the mass transport properties of fracture skins and to sue these properties in simulations of mass transport in flowing ground water. The project builds on preliminary studies on fracture-skin properties conducted at the University of Texas at Austin. These studies investigated both welded tuffs and Paleozoic sandstones and documented fundamental changes in rock porosity, permeability, and mineralogy in the skins when compared to the unaltered rock. This project will expand this effort and will, for the first time to our knowledge, estimate the diffusion coefficients and sorptivities of fracture skins through closely controlled laboratory experiments. Two experimental apparatuses will be constructed to estimate these properties. One design will examine sorption by fractures skins in an artificial fracture-column under conditions of forced ground-water flow. The second design will utilize wafers or disks, designed for use in The University of Texas electronic minipermeameter, to measure diffusion coefficients and sorption for samples of fracture skins and unaltered rock matrices. These data will be utilized in analytical and/or numerical models to estimate how fracture skins alter the rates of mass transport. The results may be significant in problems of siting radioactive (and other) waste disposal facilities, extraction of petroleum from fractured reservoirs, and a variety of fundamental geological problems, such as diagenesis, formation of mineral deposits, and calculation of ground-water recharge. ***
