HR: 1340h
AN: H23G-1718    [Abstracts]
TI: Evolution of Nanometer-scale Pores During Mineralization in Rocks
AU: * Emmanuel, S
EM: simon.emmanuel@yale.edu
AF: Department of Geology and Geophysics, Yale University, P.O. Box 208109, New Haven, CT 06520-8109, United States
AU: Ague, J J
EM: jay.ague@yale.edu
AF: Department of Geology and Geophysics, Yale University, P.O. Box 208109, New Haven, CT 06520-8109, United States
AB: Nanometer-scale pores in geological media can change the effective solubility of minerals, allowing highly supersaturated fluids to exist within the porous medium; this process, termed pore-size controlled solubility (PCS), stems from the surface tension associated with crystals growing in rigid pores. In many ways analogous to the capillary pressure at a liquid-vapor interface within a pore, this surface tension gives rise to an excess pressure within the crystal, which can be related both to solubility and pore size. Crucially for geological media, theory predicts that minerals can precipitate when a fluid flows from small pores into larger ones, and such a mechanism could account for the preferential mineralization often observed in high-porosity zones and fractures within rocks. Here, we use numerical simulations to demonstrate how PCS could affect mineralization patterns in rocks adjacent to pressure-dissolution interfaces (stylolites). We show that in systems with constant solubility, nanometer-scale pores will close rapidly due to their high specific surface area; by contrast, when the PCS mechanism is included in the model, macro-porosity is filled first, with nano-scale pores remaining open throughout the simulations. In addition, our initial observations in stylolite-bearing rocks suggest that nano-scale pores could control the evolution of porosity in many geological systems.
DE: 1829 Groundwater hydrology
SC: Hydrology [H]
MN: 2007 Fall Meeting