Fault-Controlled Fluid Flow Within Extensional Basins and Its Implications for Sedimentary Rock-Hosted Mineral Deposits

Abstract

Abstract Normal faults commonly represent one of the principal controls on the origin and formation of sedimentary rock-hosted mineral deposits. Their presence within rift basins has a profound effect on fluid flow, with their impact ranging from acting as barriers, causing pressure compartmentalization of basinal pore fluids, to forming conduits for up-fault fluid flow. Despite their established importance in controlling the migration and trapping of mineralizing fluids, we have yet to adequately reconcile this duality of flow behavior and its impact on mineral flow systems within basinal sequences from a semiquantitative to quantitative perspective. Combining insights and models derived from earthquake, hydrocarbon, and mineral studies, the principal processes and models for fault-related fluid flow within sedimentary basins are reviewed and a unified conceptual model defined for their role in mineral systems. We illustrate associated concepts with case studies from Irish-type Zn-Pb deposits, sedimentary rock-hosted Cu deposits, and active sedimentary basins. We show that faults can actively affect fluid flow by a variety of associated processes, including seismic pumping and pulsing, or can provide pathways for the upward flow of overpressured fluids or the downward sinking of heavy brines. Associated models support the generation of crustal-scale convective flow systems that underpin the formation of major mineral provinces and provide a basis for differences in the flow behavior of faults, depending on a variety of factors such as fault zone complexities, host-rock properties, deformation conditions, and pressure drives. Flow heterogeneity along faults provides a basis for the thoroughly 3D flow systems that localize fluid flow and lead to the formation of mineral deposits.