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Effect of faceting on pore geometry in texturally equilibrated rocks: implications for low permeability at low porosity
Contributions to Mineralogy and Petrology Springer Berlin / Heidelberg
ISSN 0010-7999 (Print) 1432-0967 (Online)
Номер Volume 152, Number 2 / Август 2006 г.
DOI 10.1007/s00410-006-0099-y
Страницы 169-186

Original Paper
Effect of faceting on pore geometry in texturally equilibrated rocks: implications for low permeability at low porosity
Takashi Yoshino1, 2 , Jonathan D. Price1, David A. Wark1 and E. Bruce Watson1

(1) Department of Earth and Environmental Sciences, Rensselaer Polytechnic Institute, Troy, NY 12180, USA
(2) Institute for Study of the Earth’s Interior, Okayama University, Tottori 682-0193, Japan
Received: 15 August 2005 Accepted: 24 March 2006 Published online: 7 June 2006

Communicated by T. L. Grove
Abstract 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°) 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 shrinking 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 significantly decreased by the relative reduction of triple junction volumes or by closure of channels along grain edge due to the truncation of facet walls.

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Takashi Yoshino
Email: tyoshino@misasa.okayama-u.ac.jp
Phone: +81-858-433734
Fax: +81-858-433450


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