Episodic reactivation of carbonate fault zones with implications for permeability – An example from Provence, Southeast France

Exposed in large, continuous outcrops in Provence, southern France, the Castellas fault formed as a normal fault in the Upper Cretaceous and was reactivated as a left-lateral fault in the Eocene. Structural, petrographical, isotopic, and geochronological analyses shed light on the sequence of deformational-diagenetic stages of the fault zone and help identify properties that controlled fluid-flow behavior through time. Abrupt contrasts in fracture abundance compared to the undeformed host rock define a damage zone containing fractures arranged in regularly spaced clusters. We identified eleven episodes of calcite cementation within opening-mode fractures and host rock primary pores. Cement fabrics, sediment fills, and geochemistry show evidence of shallow burial environments. U–Pb geochronology of calcite cements indicate two main deformational phases of the fault zone during the Albo-Cenomanian Durancian uplift and Eocene Pyrenean orogeny at ca. 90 Ma and 50-40 Ma, respectively. Deformation created poro-permeability, but cementation followed shortly after, pervasively occluding most of the fault zone porosity by the end of the Eocene. •Eleven phases of cement filled opening-mode fractures and breccias in a fault zone between Albian-Cenomanian and Eocene.•Fault zone underwent two main deformational events during the Durancian uplift (∼90 Ma) and Pyrenean orogeny (50-40 Ma).•Evidence of diagenesis impacting fluid flow behavior in fault zones along time.•Fluid flow was permanently prevented due to thorough cementation by 40My ago giving place to an impermeable fault zone.