Fluid flow in extensional environments; numerical modelling with an application to Hamersley iron ores

McLellan, J.G., Oliver, N.H.S., and Schaubs, P.M. (2004) Fluid flow in extensional environments; numerical modelling with an application to Hamersley iron ores. Journal of Structural Geology, 26 (6-7). pp. 1157-1171.

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Abstract

The mechanical feasibility of focusing both surface- and basinal-derived fluids towards sites of iron ore genesis during Proterozoic deformation in the Hamersley Province is tested here by computer simulation. Finite difference modelling of porous media flow during extensional deformation of a mountain range shows that surface fluids are drawn towards areas of failure and focus into the centre of the mountain. The addition of permeable structures such as a normal fault provides focused fluid pathways in which mechanical and geological conditions are particularly conducive to both upward and downward flow. Upward flow from the base of the fault within the model overall is favoured by low permeability basement materials and supra-hydrostatic pore pressures. Downward migration of fluids becomes more prominent as extension progresses and upward fluid flow from the base diminishes. The introduction of sedimentary layering into the models allows lateral fluid flow, such that sites of potential fluid mixing may then occur within permeable iron formation units close to the fault zone. Allowing parts of the stratigraphy to become more permeable as a function of high fluid flux simulates permeability enhancement by silica dissolution as a mechanism for iron ore genesis. The involvement of both basinal and surficial fluids in the genesis of the ore deposits is supported by the mechanical models and in addition provides an explanation for a progression from relatively reduced to oxidised conditions at the Mt Tom Price deposit (and possibly other large deposits) with time.

Item ID: 4508
Item Type: Article (Research - C1)
ISSN: 1873-1201
Keywords: banded iron formations; extension; fluid flow; Hamersley Province; numerical modelling
Date Deposited: 11 Jun 2009 02:25
FoR Codes: 04 EARTH SCIENCES > 0403 Geology > 040307 Ore Deposit Petrology @ 100%
SEO Codes: 84 MINERAL RESOURCES (excl. Energy Resources) > 8401 Mineral Exploration > 840104 Iron Ore Exploration @ 100%
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