The flow of hot brines in cracks and the formation of ore deposits

We examined the thermal evolution of solutions transported vertically by turbulent flow in fractures and its implications for Mississippi Valley-type ore deposition. The main parameter governing the flow is fracture width, which determines the flow rate, volume, and thermal evolution of the transported fluid. We assumed local equilibrium and traced the chemical evolution of the transported solutions, the mineral deposits associated with the cooling of these solutions, and the limits of fracture clogging. The volume of fluid expelled and the fracture width determine the location of the deposit and, hence, the deposit type, i.e., carbonate hosted or vein. We show that a network of thin cracks can indeed transport the volume of brines needed for the genesis of large Mississippi Valley-type ore deposits, such as the Southeast Missouri lead district.