Decompartmentalisation of a Multiepisodic Fault System, Barcelona Plain, NE Spain

The Catalan Coastal Ranges are formed by a NE-SW fault system that is the result of two extensive events (Mesozoic and Neogen) and a compressive event (Paleogen). We have studied two fault zones involving basement and Triassic materials within the Barcelona Plain in the NE Iberia stated from petrological and geochemical studies. These fault zones have a core formed by brittle fault rocks that present three kinds of cements: silicic, calcitic with δ18O values between -20 and -15‰ vPDB and calcitic with δ18O values about -5‰ vPDB. The temporal and spatial relationships between these cements show the evolution of the compartmentalisation in front of fluids linked with the different deformation events from Mesozoic to recent. During the early history, both faults acted as conduits for very different fluids, silicic cements precipitated in one of the faults and very δ18O-depleted calcite cements precipitated in the other fault. Later, a reactivation of both faults allowed the connectivity for fluids along the two zones. Finally, when the faults reached the surface, low-temperature meteoric fluids percolated downward along the fault zones.