An integrated application of geological-geophysical methodologies as a cost-efficient tool in improving the estimation of clay deposit potential: case study from south-central Sardinia (Italy)

A multidisciplinary study attempting to improve estimation of clay deposit potential was performed using geological- geophysical techniques at Piscina Collusco, S Sardinia, Italy, a test area where a bentonite deposit outcrops. The Very Low Frequency (VLF) Electromagnetic (EM) method, a cost-effective method suitable for detecting lateral electrically resistive host rock/electrically conductive clay deposit contacts, was applied. Geophysical investigation yielded information on the lateral and indepth continuity of the mineralisation, e.g., geometric features, strike and dip of the mineral body, and the geological-structural features of the area. Test drilling, carried out to calibrate geophysical data, confirmed that the high-conductivity zones are related to the presence of bentonite and that the clay mineral body is developed at depth. Data integration showed that higher-conductivity values are related to the highest clay contents. Results show that this multidisciplinary approach improves resource estimation at minimum cost, and can be successfully used in mineral exploration in similar geological contexts. This could play an important role in assessing the economic potential of new industrial mineral deposits, and/or in optimising mining in active quarries. Following the interpretation of the integrated data in this case study, resources initially evaluated at 394,000 t, were found to be in the order of 3,786,000 t.