Abstract

Summary Kimberlites are the main sources of diamonds. In field geophysics kimberlite pipes are characterized by anomalies of low resistivity. However, the reason for high electrical conductivity is not clear. We have carried out multi-salinity experiments with two kimberlite samples (autolitic and xenotuffisitic breccia) from Arkhangelsk region (Lomonosova Deposit). Samples were saturated with brines of different electrical conductivity values (from 0.01 to 3.77 S/m). Complex electrical conductivity was measured with SIP FUCHS-III instrument in the frequency range from 1.43 mHz to 20 kHz. We found the bulk conductivity of sample is larger than that of the pore water (at the brine electrical conductivity range typical for fresh water). The quadrature conductivity values at 1.46 Hz are larger than that typically obtained for e.g., magmatic rocks and sandstones. We attribute this complex conductivity behavior to the surface conductivity influence. Furthermore, our kimberlite samples have a high values of cation-exchange capacity (CEC). It can be explained by the presence of smectites in mineral composition.

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