HR: 0800h
AN: V41A-1436    [Abstracts]
TI: Effect of faceting on pore geometry in texturally equilibrated rocks: implications for permeability at low porosity
AU: * Yoshino, T
EM: tyoshino@misasa.okayama-u.ac.jp
AF: Institute for Study of the Earth's Interior, Okayama University, Yamada 827, Misasa, Tottori, 682-0193 Japan
AU: Price, J D
EM: pricej@rpi.edu
AF: Department of Earth and Environmental Sciences, Rensselaer Polytechnic Institute, 110 8th Street, Troy, NY 12180 United States
AU: Wark, D A
EM: warkd@rpi.edu
AF: Department of Earth and Environmental Sciences, Rensselaer Polytechnic Institute, 110 8th Street, Troy, NY 12180 United States
AU: Watson, E B
EM: watsoe@rpi.edu
AF: Department of Earth and Environmental Sciences, Rensselaer Polytechnic Institute, 110 8th Street, Troy, NY 12180 United States
AB: Movement of fluid or melt may play a significant role in a variety of geological processes, including planetary differentiation, magma genesis, metasomatism, seismicity and heat transport. The permeability of rocks is strongly controlled by pore geometry. The pore geometry of texturally equilibrated rocks is controlled by the interfacial energy ratio between grain boundaries and solid-liquid boundaries. Faceting at pore walls, which is a common feature of pore networks in rocks, strongly affects the liquid distribution. We investigated the effects of faceting on the equilibrium pore geometries based on image analysis of several systems with various degrees of faceting and dihedral angles. The degree of faceting was assessed by the F value, which is the ratio of the flat interface length at the pore wall to the length of total interfacial boundary between solid and liquid. The F values tend to increase with increasing liquid volume fraction. Little-faceted systems show relatively homogeneous liquid distribution. Moderately-faceted systems with a higher dihedral angle (55 degrees) are characterized by development of large pores surrounded by faceted walls and complementary shrinkage of triple junction tubes, whereas strongly faceted systems with a low dihedral angle show no evidence of shrink of triple junction tubes, although most pores are surrounded by faceted pore walls. The faceted systems tend to produce more facet boundaries at the pore walls due to the difference of interfacial energies between the flat and curved surfaces. In the systems with the same degree of faceting, heterogeneity of liquid distribution tends to decrease with dihedral angle. For faceting systems, the permeability of texturally equilibrated rocks with low liquid fraction would be extremely decreased by the relative reduction of triple junction volumes or by closure of channels along grain edge due to the truncation of facet walls.
DE: 3625 Petrography, microstructures, and textures
DE: 3630 Experimental mineralogy and petrology
DE: 5112 Microstructure
DE: 5114 Permeability and porosity
DE: 5139 Transport properties
SC: Volcanology, Geochemistry, Petrology [V]
MN: Fall Meeting 2005