Citation

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Derrick, G.M., 1982. A Proterozoic rift zone at Mount Isa, Queensland, and implications for mineralisation. BMR Journal of Australian Geology and Geophysics  7:2:81-92. Bureau of Mineral Resources, Geology and Geophysics, Canberra.

Abstract

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.
Google map showing geographic bounding box with values North bound -18.0 East bound 143.0 West bound 138.0 South bound -24.0
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Creative Commons Attribution 4.0 International Licence

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Commonwealth of Australia (Geoscience Australia)

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Date (publication)

1982

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geoscientificInformation

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GA Publication
Journal
Earth Sciences

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English

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unclassified

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-18.0
East bound
143.0
West bound
138.0
South bound
-24.0

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Unknown

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pdf

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ANZLIC Metadata Profile: An Australian/New Zealand Profile of AS/NZS ISO 19115:2005, Geographic information - Metadata

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1.1

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2015-03-23

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Canberra
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