マグマのガス浸透率データ解析におけるパーコレーション理論の役割

概要

論文の詳細を見る
Permeability data for natural and experimental products of magma that have been reported by several studies are reanalyzed on the basis of percolation theory. I use a power-law relationship between gas permeability k and porosity φ with a critical porosity φc and a critical exponent e in the form, k ∝ (φ-φc)e, after reviewing some dependences of φc and e on characteristics of porous media. As a result, the k-φ data of silicic magmas from non-explosive eruptions are found in a whole region containing two models of continuum percolation: Swiss-cheese model (φc ∼ 0%, e ∼ 4.5) and inverted Swiss-cheese model (φc ∼ 30%, e ∼ 2), and no data clearly denotes φc much higher than 30%. I also point out that it is necessary to consider careful textural characteristics of porous samples in analyzing the k-φ data in order to assess the process of formation of the texture adequately. Important textural characteristics are i) cross-sectional area of gas channel used for normalizing k because of estimating appropriate values of φc and e, ii) elongation of pore and alignment of the direction, and iii) sample scale defined as a ratio of the sample length to a characteristic length of the major axes of elongated pores, because φc depends on the degree of the elongation, the alignment and the sample scale.
2006-05-30