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A Proterozoic rift zone at Mount Isa, Queensland, and implications for mineralisation

Created 16/10/2025

Updated 16/10/2025

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The Leichhardt River Fault Trough (LRFT) near Mount Isa is thought to be an ensialic or continental margin rift structure formed about 1800-1650 m.y. ago. Extension in old (1865-1800 m.y.) acid volcanic and granitic basement was followed by deposition of up to 10 km of epicontinental clastics, minor dolomite and redbeds, and marginal fanglomerates, and up to 6 km of subaerial to shallow subaqueous basalt. The latter provides characteristic gravity and magnetic signatures, which define the subsurface extent of the rift. The rift fill is blanketed by an orthoquartzite-carbonate unit about 1750 m.y. old. Deformation and uplift 1680 m.y. ago were accompanied by basic to acid volcanicity, which was followed by intracontinental sedimentation, and finally by 4-6 km of Pb-Zn-bearing dolomitic shale basin deposits. A zone of central uplift (Mount Gordon Arch) divided the LRFT into two meridional basins. Igneous rocks from the LRFT are bimodal in composition, and typical of non-orogenic terrains. They range from basement rhyolite and dacite to tholeiitic basalt, granite and alkali granite, rhyolite and trachybasalt, and finally to tholeiitic dyke swarms. The fault trough formed by extension and sagging of continental crust. Mantle upwelling and subsequent deep rifting tapped basalt sources; magma withdrawal and basalt loading of the crust led to further sagging and epicontinental sedimentation. Heat from earlier mantle upwelling caused lower crustal fusion and subsequent granite intrusion of the rift pile. Genesis of major Cu and Pb-Zn deposits has been partly controlled by early and reactivated growth faults and by the movement of subsidiary crustal blocks within the fault trough.

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Field Value
Title A Proterozoic rift zone at Mount Isa, Queensland, and implications for mineralisation
Language eng
Licence Not Specified
Landing Page https://data.gov.au/data/dataset/40f68fc0-14b1-47f8-93be-ec7489e23659
Contact Point
Geoscience Australia Data
clientservices@ga.gov.au
Reference Period 20/04/2018
Geospatial Coverage
Map data © OpenStreetMap contributors
{
  "coordinates": [
    [
      [
        138.0,
        -24.0
      ],
      [
        143.0,
        -24.0
      ],
      [
        143.0,
        -18.0
      ],
      [
        138.0,
        -18.0
      ],
      [
        138.0,
        -24.0
      ]
    ]
  ],
  "type": "Polygon"
}
Data Portal Geoscience Australia

Data Source

This dataset was originally found on Geoscience Australia "A Proterozoic rift zone at Mount Isa, Queensland, and implications for mineralisation". Please visit the source to access the original metadata of the dataset:
https://ecat.ga.gov.au/geonetwork/srv/eng/csw/dataset/a-proterozoic-rift-zone-at-mount-isa-queensland-and-implications-for-mineralisation