Spectral induced polarization (SIP) is a geophysical technique that is widely used to determine the properties of rock and soils by measuring the complex impedance over a range of frequencies. The method can be used to detect metallic and non-metallic mineralization. The characterization of electronically conductive minerals with SIP has long been of interest to the mineral exploration sector. However, a better understanding of the effects of mineral texture on SIP signals in the presence of electron-conducting minerals is required. In this study, laboratory measurements were performed on electron-conducting minerals to better understand the effects of disseminated and veinlet minerals on SIP signatures. We observe that veinlet minerals generate a strong non-linear SIP effect and a longer non-equilibrium process compared to the disseminated form of the same minerals. This textural effect is assumed to result from differences in the SIP response associated with faradaic versus non-faradaic polarization processes that both occur at the metal-solution interface. Charge transfer between ionic and electronic conduction occurs via oxidation or reduction reactions between the solution and metallic mineral interface. While charge cannot cross the interface under non- faradaic conditions, the faradaic current has the capability to pass across the phase boundary via electron transfer. Two significant parameters are considered as evidence of the faradaic polarization process. First, the non-linear SIP effect, being a variation in the response as a function of applied current represents the response to faradaic currents. Second, non-equilibrium effects, whereby the SIP response varies with time, results from electrochemical reactions associated with redox-active ions involved in the faradaic current transfer across the metal interface. We also observe that whereas disseminated samples are well-described by the classic Pelton model, this is not the case for veinlet samples. Such non- linear and non-equilibrium SIP signals may prove valuable for discriminating disseminated from veinlet texture associated with electron-conducting minerals.

Open-Access Online Publication: May 29, 2023