Full 3D Inversion of Electrical Resistivity Tomography Data for a Gypsum Underground Quarry (NW Italy)

We present the characterization of an underground gypsum quarry by means of electrical resistivity tomography (ERT) data, with a full 3D approach from the field data acquisition to the modelling. 3D ERT ensures longitudinal and transversal data coverage and model accuracy in complex areas. The site is currently under exploitation and is located in Murisengo (Piedmont, NW Italy). The objective of the survey was to characterize the subsurface for potential future mining enlargement. The proposed methodology is based on the acquisition of a high number of 2D and 3D data thanks to a devoted equipment and customized quadrupole sequences. 3D inversion, despite being computational demanding, was performed to recover the subsurface resistivity distribution below six ERT lines. The results revealed that the centre of the investigated area has high resistivity values (above 160 Ωm), while the northern and western regions are conductive (below 20 Ωm). Inspection of the 3D model allowed a clear identification of the high resistivity regions that are expected to host the orebody (or, in other words, the portion of the rock unit with the highest gypsum fraction). These outcomes clearly highlight the region where the quarry company should expand the exploration activity.