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Abstract: This research presents a numerical simulation of the regional scale hydrothermal fluid flow over an E-W geological profile in the Northern Lawn Hill Platform, Australia, at 1575 Ma. The modeling work assesses favorable hydrological scenarios for the formation of stratiform Zn–Pb-Ag SEDEX deposits by buoyancy driven free convection of hydrothermal fluids. Based on recent geological mapping and stratigraphic interpretation, our conceptual model depicts the stratigraphy in the area at the time of mineralization at a finer resolution than previous simulations in the area. The stratigraphic sequence consists of three cycles of clastic and carbonate basin fills, cut by several major syn-sedimentary faults. FEFLOW, a 3D finite element code, is used to simulate fluid flow and coupled heat transfer. Based on a two dimensional simulation, the authors aim to gain insight into the regional groundwater circulation and heat redistribution, discharge at the surface by conduits of faults, and the impact of fluid flow on the mineral precipitation in diagenetic aquifers and deposition on the sea-floor at the vents of discharging faults. The evolution of the hydrothermal system is simulated based on the key hydraulic parameters controlling the paleo fluid flow pattern and heat transport. Numerical simulations indicated the relationship between faults and aquifer sequences as being a major factor controlling buoyancy driven convection. A sensitivity analysis performed for different scenarios by varying relationships between aquifers and syn-sedimentary faults offers a better understanding of the hydrogeological constraints on the genesis of major SEDEX deposits. The purpose of the present study was to target prospective Zn–Pb deposits in the Northern Lawn Hill platform, the Mt. Isa basin by buoyancy driven fluid flow and heat transport.

Keyword: numerical modeling, hydrothermal, Isa, Lawn Hill, SEDEX.