Abstract

Fracture characterization in granites has been an important subject of study during these last years, by means of geological-structural cartography, hydrogeology and geochemical analysis. All these works have been carried out to investigate the hydromechanics and permeability in low-permeability rocks. In this study we apply a surface geophysical method in order to characterize the permeability of the fault zones affecting “El Berrocal” granite (Central System, Spain). The low-induction electromagnetic method (EM) gives us the apparent resistivity values of the rocks at a maximum depth, allowing us to differentiate between soil / altered rock from fresh granites. As the apparent resistivity depends on the granite alteration and/or the water content, this parameter allows to estimate the relative permeability of different fracture zones. The obtained results show that the high-permeability fractures are those that are larger ones which were active during Alpine deformation (Eocene-present).