Abstract

Numerical solutions of the equations for fluid flow, heat and mass transport, and geochemical reactions are used in this study to quantify the role of regional ground-water flow in the genesis of the carbonate-hosted lead-zinc deposits at Pine Point. The numerical modeling is performed along a vertical section oriented parallel to the Keg River barrier complex in order to test the hypothesis that southwest to northeast flow of topography-driven brines controlled ore formation.A sensitivity analysis is used to show that gravity-driven flow systems were capable of providing favorable fluid flow rates, temperatures, and metal concentrations for ore formation near the eastern edge of the Western Canada basin. Mass transport simulations support a genetic model whereby metal sulfate-bearing brines are focused through the Keg River barrier aquifer, and ore deposition resulted from sulfate reduction. The modeling results suggest paleoflow rates of 1 to 5 m/yr, paleoconcentrations of zinc on the order of 1 to 5 mg/kg H 2 O, and paleotemperatures in the range to 60 degrees to 100 degrees C. Under these possible site conditions, the Pine Point deposits could have formed over a time interval of 0.5 to 5.0 million years. Ore genesis likely took place in post-Cretaceous time, due to the emergence of the Rocky Mountains.

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