In order to interpret spectral induced polarization (SIP) data measured in the field for the purpose of mineral exploration, laboratory investigations are necessary that establish relationships between electrical parameters and mineral properties. For massive ores, and in particular for seafloor massive sulfides (SMSs), samples may be difficult to obtain, and it is often not desired to cut cylindrical plugs out of the available hand pieces. We suggest a method to obtain the electrical spectra of hand pieces from measurements on the samples embedded in a non-polarizing medium, in our case quartz sand. As such, destroying potentially precious samples is not necessary. The frequency-dependent phase spectrum of the sample is calculated by dividing the bulk spectrum with a so-called dilution factor, which is obtained from numerical simulation and has a real and constant value. We evaluate the method with a set of SMS samples where conventional cylindrical plugs are available. We can estimate the phase shift maximum of 73% of the samples with a deviation less than 50% from the reference. The estimation quality slightly decreases if the dilution factor is approximated by the volumetric share of the sample. We consider the performance acceptable if the general difficulty to obtain reproducible and representative laboratory measurements for massive sulfides is taken into account.

We carried out spectral-induced polarization (SIP) measurements on a set of dried seafloor massive sulfide samples and compared the results with those obtained with the same samples fully saturated with NaCl solution. We find that the conductivity and polarizability are generally high for both dried and saturated samples, i.e., exhibiting phase shifts in the order of 100 s of mrad and imaginary conductivities up to 1 S/m. Depending on the particular sample, the polarizabilities of the dried samples remain as high as for the saturated samples or are slightly reduced. The high polarizability of dried samples and the fact that polarizability cannot be destroyed by drying are significant observations because most of the existing theories to explain the polarization of mineralized rock assume a pore space filled with an electrolyte. We also found that the often-used agar gel is unsuitable for coupling the dried samples to the electrodes because it releases water into the sample. Coupling with plasticine is a feasible alternative because significantly less fluid is absorbed by the sample when it is incorporated into the sample holder.