ABSTRACT We investigate the complex conductivity behaviour of natural volcanic rocks containing variable amounts of smectite in multi‐salinity experiments. We compare the results with relationships established for sandstones. Considering only samples with little volume of metallic particles, we observe similar and small phase‐angles at low frequency for all samples at all salinities (less than 25 mrad at 1 Hz). Yet, a wide range of cation exchange capacity, porosity and formation factor is covered by the sample set: 0.5–50 meq/100 g, 4–40% and 18–780, respectively. Our results show that, in the absence of metallic particles, the ratio between imaginary conductivity and surface conductivity is significantly lower for altered volcanic rocks than for sandstones and decreases with the smectite content. These observations indicate that an increased smectite content causes more conduction and less polarization, which could be explained by the onset of a continuous conduction pathway throughout connected interfoliar spaces of smectite. Due to this pathway, cations from the pore fluid may penetrate the solid lattice, for example through connected smectite aggregates clogging the fracture network, thus preventing polarization. We also observe that the relationship between imaginary conductivity and surface conductivity, at one salinity or over the whole salinity range, is not more significant than the relationship between the imaginary conductivity and the total real conductivity. Therefore, we suggest that the imaginary conductivity cannot be used to discriminate the contributions from smectite and pore water to the total conductivity of altered volcanic rocks.

中文翻译：

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蒙脱石和盐度对火山岩虚电导率和表面电导率的影响

摘要 我们在多盐度实验中研究了含有不同量蒙脱石的天然火山岩的复杂电导行为。我们将结果与为砂岩建立的关系进行比较。仅考虑具有少量金属颗粒的样品，我们在所有盐度（1 Hz 时小于 25 mrad）的所有样品的低频下观察到相似且小的相位角。然而，样本集涵盖了广泛的阳离子交换容量、孔隙率和形成因子：分别为 0.5–50 meq/100 g、4–40% 和 18–780。我们的结果表明，在没有金属颗粒的情况下，蚀变火山岩的假想电导率和表面电导率之间的比值显着低于砂岩，并且随着蒙脱石含量的增加而降低。这些观察结果表明，增加的蒙脱石含量会导致更多的传导和更少的极化，这可以通过贯穿蒙脱石连接的叶间空间的连续传导途径的开始来解释。由于这种途径，来自孔隙流体的阳离子可以穿透固体晶格，例如通过连接的蒙脱石聚集体堵塞裂缝网络，从而防止极化。我们还观察到，在一种盐度或整个盐度范围内，虚电导率和表面电导率之间的关系并不比虚电导率和总实际电导率之间的关系更显着。所以，