Fig. 9From: On the geothermal potential of crustal fault zones: a case study from the Pontgibaud area (French Massif Central, France)Three-dimensional observations of the planar and matrix porosity of one sample taken from the Pontgibaud fault zone. The red color of figures a, b corresponds to mineralization (lead sulphides). The yellow color of figures a, b corresponds to the planar porosity located on the fracture walls. The yellow color of figure c could correspond to the matrix porosity. The resolution of figures a–c is, respectively, 25, 25 and 4 μmBack to article page