Publication Date:
2023-05-17
Description:
Electromagnetic surveys such as magnetotellurics are known to be sensitive to the presence of smectite, which is abundant in subduction zones. However, the contribution of smectite to bulk conductivity is complex and still needs to be quantitatively understood better. Therefore, in this study, we investigated the effect of smectite on bulk conductivity by numerical modeling using the finite element method. In our simulations, we investigated the effects of four conditions: porosity, fraction of smectite in the quartz matrix, temperature, and NaCl concentration of pore water. Here, we randomly assigned each element's conductivity tensor of either material: smectite, quartz, or pore water. In addition, we introduced an anisotropy to the conductivity tensor of smectite between the directions parallel and perpendicular to the T-O-T layer. Meanwhile, the conductivity tensors of quartz and pore fluid were considered isotropic. The simulation results showed that the spatial arrangement of the materials significantly affected the bulk conductivity for the porosity greater than 0.01. In contrast, for smaller porosity, the effect of the spatial arrangement was almost negligible, and the volume fraction of smectite, pore water salinity, and temperature controlled the bulk conductivity. These results suggest that proper parameterization of the element arrangement patterns is essential when calculating the bulk conductivity of smectite-bearing rocks.
Language:
English
Type:
info:eu-repo/semantics/conferenceObject
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