Research paperRemobilization of deep basin brine during exhumation of the Illizi Basin, Algeria

- Ordovician-hosted brines genetically linked to younger Triassic-Liassic evaporites.
- Evidence for long-distance fluid migration over >400 km.
- Up-dip fluid flow event linked to major exhumation of the Illizi Basin.
- Exhumation-related fluid flow possibly caused by breaching of overpressure system.

Understanding the processes that drive fluid flow in sedimentary basins has important implications for models of metallic ore and petroleum migration and accumulation in the subsurface. Potential drive mechanisms include gravity-driven flow, compaction-driven flow, and density-driven convection. In this study, we demonstrate that the brine hosted in Ordovician sandstone in the Illizi Basin in Algeria is genetically linked to Triassic-Liassic evaporites deposited >400 km to the north in the Berkine Basin. This observation confirms that long distance, lateral, brine migration has occurred within the basin in the past. We assess the hydrogeologic record preserved in aqueous fluid inclusions within the Ordovician sandstone, document a marked increase in formation water salinity during cooling and exhumation, and evaluate the drive mechanisms for late-stage remobilization of deep brines within the basin. It is hypothesized that the release of overpressure during exhumation of the Illizi Basin may have been a critical contributor to updip fluid flux. This model could be applicable to other exhumed basins worldwide.