Fig. 4

Photomicrographs (optical microscope and cathodoluminescence) of the Calcaires Récifaux unit. a, b Multi-phased incomplete blocky calcite cementation leaving intra-crystalline porosity in the HU-2 well (sample YM49). c, d Dedolomitization as observed in the Prapont section (sample YM55). e, f Replacement planar dolomite overprinting pre-existing blocky calcite cementation in the Roche Blanche section (sample YM8). g Intensively fractured micritic limestone in the Champfromier section. The calcite filling the fracture exhibits thin twinning (sample YM14). f The same sample in natural light (top left) and under cathodoluminescence displaying a dissolution enhanced fracture filled by non-luminescent calcite