Fluid Dynamics in a Thrust Fault Inferred from Petrology and Geochemistry of Calcite Veins: An Example from the Southern Pyrenees

Figure 13

Fluid flow model during the evolution of the studied thrust (not to scale) showing the relationships between synkinematic fracture development, the stress state at each deformation phase, and the involved fluid flow event. (a) During initial fault growth, deformation was concentrated in the process zone (around the fault tip) allowing the formation of fractures F1 and randomly oriented fractures (mosaic to chaotic breccia). During this episode, meteoric fluids infiltrated at high structural reliefs, warmed at depth, and then migrated through diffused deformation around the fault tip. (b) During progressive deformation, new fractures develop and meteoric fluids evolved at increasing depths and temperatures. During these two initial fracturing events (F1-F2), the remote stress field varied locally within the process zone to generate steeply dipping fractures. (c) As the thrust developed, fractures F3 were formed in the footwall damage zone. The orientation of these fractures reflects the far-field stress regime unaltered by faulting. The fluid involved in this stage evidences the continuous increase in precipitation temperatures due to burial during thrust emplacement. From this stage, the thrust drained fluids that only infiltrated in the hanging wall. These fluids were likely expelled from underlying Cretaceous carbonates due to rock compaction during thrusting.