Structural controls on development and localization of syntectonic copper mineralization at Mount Isa, Queensland

Bell, T. H.; Perkins, W. G.; Swager, C.P.

doi:10.2113/gsecongeo.83.1.69

Cited by 57 publications

(45 citation statements)

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“…The Urquhart Shale, which hosts both the lead-zincsilver and the copper mineralisation, is part of the Mount Isa Group, a Mesoproterozoic series of carbon-rich siliciclastic sediments and carbonates, which were deposited during a sag-phase following the third major rifting event in the Mount Isa Inlier (Betts et al 2006). A number of detailed studies (Bell et al 1988;Perkins 1984;Swager 1985) concluded that copper ore was deposited after the main tectono-metamorphic events of the Isan Orogeny, and postdates the lead-zinc-silver mineralisation at the same location. According to recent geochemical studies Gregory et al 2005;Kendrick et al 2007) alteration and copper mineralisation involved several fluids, including an upward flowing basement-equilibrated reduced fluid, and an oxidised brine originating from near-surface reservoirs.…”

Section: Geological Backgroundmentioning

confidence: 99%

Coupled Models of Brittle-plastic Deformation and Fluid Flow: Approaches, Methods, and Application to Mesoproterozoic Mineralisation at Mount Isa, Australia

Gessner

2009

Surv Geophys

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Rock deformation has an important effect on the spatial distribution and temporal evolution of permeability in the Earth's crust. Hydromechanical coupling is of fundamental significance to natural fluid-rock interaction in porous and fractured hydrothermal systems, and in the assessment and production of hydrocarbon resources and geothermal energy. Shearing and fracturing of rocks can lead to the creation or destruction of permeability when fractures or faults form, or when existing structures are reactivated. Changes in stress orientation or fluid pressure can drive rock failure and create dilating fault zones that have the potential to focus fluid flow, or to breach seals above overpressured fluid compartments. Here, numerical models of deformation and fluid flow related to Mesoproterozoic copper mineralisation at Mount Isa, Australia, are presented that show how changes in deformation geometry in multiply deformed geological architectures relate to changes in dilation patterns, fluid pathways and flow geometry. Coupled numerical simulations of deformation and fluid flow can be useful tools to better understand structural control on fluid flow in hydrothermal mineral systems.

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Section: Geological Backgroundmentioning

confidence: 99%

Coupled Models of Brittle-plastic Deformation and Fluid Flow: Approaches, Methods, and Application to Mesoproterozoic Mineralisation at Mount Isa, Australia

Gessner

2009

Surv Geophys

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“…In addition to a large number of mines, there are hundreds of documented mineral occurrences, as well as ubiquitous evidence for potassic and sodic alteration zones and hydrothermal breccias. At Mount Isa approximately 22 million tonnes of copper precipitated as chalcopyrite during a hydrothermal brecciation event in the silicified portion of the multiply deformed Urquhart shale (e.g., Bell et al 1988). In the study presented here, we compare results from separate models on the Mount Isa system that focus on single processes like thermally driven flow Kühn and Gessner 2009a-this volume) and deformation driven flow (Gessner 2009-this volume), but we also consider reactive transport processes (Kühn 2009-this volume) to constrain copper mineralisation.…”

Section: Mount Isa Copper Systemmentioning

confidence: 99%

“…The sequence of deformation events at Mount Isa mine has been established by Bell et al (1988), as E-W shortening, followed by top-to E simple shear and subsequent dextral strikeslip with a vertical component of W-up and E-down slip parallel to the strike of the Mount Isa and Paroo faults during mineralisation (see also Gessner et al 2006;Wilde et al 2006). Hydromechanical modelling has shown that the application of these strain geometries to a mine-scale model has a significant impact on the flow patterns (Fig.…”

Section: D Mine Scale Modelsmentioning

confidence: 99%

Testing Hypotheses for the Mount Isa Copper Mineralisation with Numerical Simulations

Kühn¹,

Gessner²

2009

Surv Geophys

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We have applied reactive transport simulations to evaluate conceptual models of hydrothermal fluid flow related to the Mesoproterozoic Mount Isa copper mineralisation. Numerical experiments have been performed specifically to investigate whether fluid flow was driven by mechanical deformation, higher than hydrostatic fluid pressure gradients, or thermal buoyancy, and what the mechanism of ore deposition was. One distinct feature of the Mount Isa mineralising system is a region of massive silica-rich alteration that surrounds the copper ore bodies within the Urquhart shale, indicating upward flow of a cooling fluid. Hydromechanical modelling revealed that contraction and horizontal shear can produce a dilation pattern that favours upward fluid flow, whereas strike slip movement causes dilation of pre-existing vertical structures. Reactive transport models show that hydraulic head driven flow is more likely to produce a more realistic silica alteration pattern than free thermal convection, but neither process generates a flow pattern capable of precipitating copper at the appropriate location. Instead we propose that gravity driven flow of a dense oxidised basin brine led to chalcopyrite mineralisation by fluid-rock reaction.

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“…It is likely that all of these vein types formed originally by crack-seal processes (Ramsay 1980) and/or by breccia veining/replacement (Bell, Perkins and Swager 1988). They were modified in different ways by later deformation and alteration.…”

Section: Vein Morphology and Timingmentioning

confidence: 99%

“…This is attributable to fracturing and jostling of the boundaries of these earlier veins with the country rock during breccia veining in adjacent locations during D 4 (c.f. Bell, Perkins and Swager 1988).…”

Section: Replacement Texturesmentioning

confidence: 99%

The late orogenic timing of mineralisation in some slate belt gold deposits, Victoria, Australia

Forde

1991

Mineral. Deposita

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Gold mineralisation in classic Australian slate belt gold deposits at Ballarat, Bendigo, St. Arnaud and Inglewood occurred very late in the orogenic history of these rocks rather than during formation of the main "slaty cleavage". This has been revealed through the examination of microstructural relationships in gold-bearing quartz veins and their host rocks from these deposits, which has established a D1 to D, deformation-stage history and consistent timing for gold mineralisation over a wide area. The gold was deposited synorogenically but during the fourth deformation stage (D4) of the orogeny, a relatively weak event occurring two deformations after the main "slaty cleavage" producing event, D2. Previously, D 2 had been regarded as both the source and control of gold mineralisation as most of the quartz veins that occur in these deposits formed before or during this deformation event. However, most gold is hosted in breccia veins that formed during D4. The wallrock clasts within these breccia veins contain a young rotated foliation and the breccia veins are spatially associated with a paragenetically consistent alteration of the host rocks in the deposits. This alteration both crosscuts and preferentially mineralises wallrock S, allowing the timing of the breccia veins, alteration and gold deposition to be defined as syn-D 4 in age.

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Structural controls on development and localization of syntectonic copper mineralization at Mount Isa, Queensland

Cited by 57 publications

References 0 publications

Coupled Models of Brittle-plastic Deformation and Fluid Flow: Approaches, Methods, and Application to Mesoproterozoic Mineralisation at Mount Isa, Australia

Coupled Models of Brittle-plastic Deformation and Fluid Flow: Approaches, Methods, and Application to Mesoproterozoic Mineralisation at Mount Isa, Australia

Testing Hypotheses for the Mount Isa Copper Mineralisation with Numerical Simulations

The late orogenic timing of mineralisation in some slate belt gold deposits, Victoria, Australia

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