17:15 〜 19:15
[SCG54-P16] かんらん岩の弾性波速度と電気比抵抗に対する加熱処理温度の影響
キーワード：かんらん岩、弾性波速度、電気比抵抗、クラック、異方性、空隙率
Elastic wave velocity and electrical resistivity, which are sensitive to the pore fluid (crack) in rocks play an important role to understand the distribution of water in oceanic plate. Many previous experimental studies used the thermally treated samples indicate that the porosity increases with increasing the thermally treated temperature, resulting the change of physical properties (e.g.,Nasseri et al., 2009; Wang et al., 2013). However, there are few studies using anisotropic medium such as peridotite. In this study, I measured elastic wave velocity and electrical resistivity of peridotite thermally treated at 500℃, 600℃ and 700℃, and investigated the relationship between the anisotropy of these physical properties and the thermally treated temperature.
The cube specimens of peridotite collected from the Horoman Peridotite Complex in the Hidaka metamorphic belt, Hokkaido, were used in the experiments. Elastic wave velocity and electrical resistivity were measured in three orthogonal directions of cube specimen (X, Y and Z directions). Elastic wave velocities (compressional and shear wave velocities) under dry and wet conditions were measured by the pulse transmission method at a resonate frequency of 1 MHz. Electrical resistivity was measured by an alternative current impedance method using LCR meter at a frequency of 1 kHz. In wet condition, each sample was saturated with brine (0.5 mol/L NaCl solution). The pore volume of each specimen was measured from the difference between dry and wet masses. Porosity was determined from the pore volume and the bulk volume calculated from the sample length.
Experimental results showed that porosity increased with increasing thermally treated temperature, resulting that elastic wave velocity and electrical resistivity decreased. The anisotropy of compressional wave velocity under dry condition increased with increasing porosity, on the other hand, that of electrical resistivity decreased, suggesting that the preferred orientation of cracks and the development of crack network. In this presentation, I will discuss the distribution of thermally cracks in peridotite based on these experimental results.
The cube specimens of peridotite collected from the Horoman Peridotite Complex in the Hidaka metamorphic belt, Hokkaido, were used in the experiments. Elastic wave velocity and electrical resistivity were measured in three orthogonal directions of cube specimen (X, Y and Z directions). Elastic wave velocities (compressional and shear wave velocities) under dry and wet conditions were measured by the pulse transmission method at a resonate frequency of 1 MHz. Electrical resistivity was measured by an alternative current impedance method using LCR meter at a frequency of 1 kHz. In wet condition, each sample was saturated with brine (0.5 mol/L NaCl solution). The pore volume of each specimen was measured from the difference between dry and wet masses. Porosity was determined from the pore volume and the bulk volume calculated from the sample length.
Experimental results showed that porosity increased with increasing thermally treated temperature, resulting that elastic wave velocity and electrical resistivity decreased. The anisotropy of compressional wave velocity under dry condition increased with increasing porosity, on the other hand, that of electrical resistivity decreased, suggesting that the preferred orientation of cracks and the development of crack network. In this presentation, I will discuss the distribution of thermally cracks in peridotite based on these experimental results.