The role of geopressure zones in the formation of hydrothermal Pb-Zn Mississippi Valley type mineralization in sedimentary basins

Abstract

Geopressure zones immediately subjacent to platform carbonate rocks can be

Mineralogical and Geochemical Constraints on the Genesis of the Carbonate‐Hosted Jebel Ghozlane Pb–Zn Deposit (Nappe Zone, Northern Tunisia)

“…This and the likely association of the deposits with either the Late Miocene orogeny or the Neogene volcanism suggest that hydrothermal karstification, which has been reported at other MVT deposits elsewhere (e.g. Fowler, ; Bouch et al ., ; Gutzmer, ), was an important mechanism, rather than replacement, for generating mainly pre‐mineralization porosity in the Triassic dolostones (cf. Nicolini, ; Rouvier, ; Mansouri, ; Rouvier et al ., ; Slim‐Shimi & Tlig, ).…”

Basin Fluid Mineralization during Multistage Evolution of the Lanping Sedimentary Basin, Southwestern China

“…Since the lateral permeability is always higher than the vertical permeability in a sedimentary pile, basin fluids driven by compaction and heat convection mainly migrate laterally along aquifers with higher permeability (Bjrlykke, 1993(Bjrlykke, , 1994Deming, 1994). These overpressured zones normally have a high geothermal gradient (Fowler, 1994). Thus, they are unimportant to the effective accumulation of ore substances.…”

“…Fluids transferred in this way can gradually lose their potential and kinetic energy through reequilibrium in heat and materials with wall rocks during their continuous, slow, and long-distance migration. Such a rapid and episodic fluid flow could sustain the energy and material brought from the deep part (Fowler, 1994). We think that the basin fluids, which might be significant for solution, transportation and precipitation of metal components, are mainly overpressured hydrothermal fluids accumulated in undercompacted zones of the basins with rapid sedimentation and subsidence under an extensional tectonic setting.…”

“…As a result, the pore water will gather into the under-compacted, highly permeable sandy units below pelitic aquifuges under the effects of diffusion, filtration and capillarity (primary migration), and thus form overpressured hydrothermal fluid zones. These overpressured zones normally have a high geothermal gradient (Fowler, 1994). During the primary migration, metal components absorbed by sediment particles in "source rocks" entered into the overpressured hydrothermal fluid system in the form of inorganic or organic complexes.…”

“…The overpressured hydrothermal fluids system was normally in an unstable state and both tectonic activities (especially activities of synsedimentary faults) and hydrofracturing could account for the upward flow of hydrothermal fluids from the overpressured zones along faults (secondary migration). Such a rapid and episodic fluid flow could sustain the energy and material brought from the deep part (Fowler, 1994). Subsequent rapid cooling, boiling or reaction with suitable wall rocks of the fluid in the shallow area would then cause metal precipitation and formation of the sedimentary rock-hosted ores, the exhalative stratiform ores, the Mississippi valley type ores, and/or the hot-spring ore deposits (Bjrlykke, 1993).…”