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Mount Isa, Mt Isa, Copper - X41 and Enterprise Mines
Queensland, Qld, Australia
Main commodities: Cu Co

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The Mt Isa copper orebodies are located with north-west Queensland, Australia, adjacent to and exploited separately from the Mt Isa lead-zinc deposits (#Location: 20° 43' 42"S, 139° 28' 47"E).

This record will be substantially updated in the near future. For details of the setting and host stratigraphy see the separate Mount Isa Zinc and George Fisher records,

The Mount Isa copper ore deposits are hosted within the Mesoproterozoic (1653 Ma) Urquhart Shale, an around 1000 m thick succession of carbonaceous, pyritic, dolomitic siltstone that belong to the Mt Isa Group, which lies within the Leichhardt River Fault Trough, and belongs to Cover Sequence 3 in the Western Fold Belt of the Mt Isa Inlier.

In the Mt Isa mine area, the Mt Isa Group strikes north-south and has a persistent westerly dip of 65°. It is around 4000 m in thickness and comprises a sequence of alternating units of dolomitic shale and dolomitic siltstone, with relatively minor conglomerate and sandstone at the base. These latter sediments thicken to the east.

Cover Sequence 3 unconformably overlies the thick mafic volcanics and quartzites of Cover Sequence 2 which includes the 7000 m thick Eastern Creek Volcanics.

The individual copper orebodies are contained entirely within a single large irregular silica-dolomite alteration mass which lies to the south of and overprints the Zn-Pb-Ag orebodies, but lie within the Urquhart Shale.

There is evidence to suggest that the silica-dolomite and Cu ore are substantially younger than the Zn-Pb-Ag ore, possibly being emplaced during D3 deformation.

The silica-dolomite mass has a strike length of at least 2600 m, maximum width of 530 m and up-dip extent of near 1000 m. Its boundaries cut across bedding. The main gangue minerals are ferroan dolomite and quartz with locally important talc, chlorite and K-feldspar. The silica-dolomite comprises an early progressive growth of exaggerated dolomite grains and porphyroblastic dolomite replacement forming pseudo-breccias via replacement outwards from fractures. This stage destroys earlier textures. The silica replacement stage results in partial to complete pseudomorphic silica replacement of the dolomitic pre-cursors and preserves pre-existing textures.

The main sulphides are pyrite and chalcopyrite with lessor pyrrhotite and cobaltite. They are predominantly present as replacements forming coarse grained aggregates, pseudo-breccias and discontinuous veinlets. Chalcopyrite deposition is largely controlled by coarsely crystalline dolomite precursors.

Past production and reserves indicate a total resource of around 225 Mt @ 3.3% Cu.

JORC compliant ore reserves and mineral resources (at June 2006) are as follows (X-Strata 2007):
  X41 Mine, 1000 & 1900 orebodies
      Proved reserves - 28 Mt @ 2.1% Cu
      Probable reserves - 21 Mt @ 1.8% Cu
      Measured resources - 76 Mt @ 2.1% Cu
      Indicated resources - 7 Mt @ 1.8% Cu
      Inferred resources - 10 Mt @ 2% Cu
  Enterprise Mine, 3000 & 3500 orebodies
      Proved reserves - 32 Mt @ 3.6% Cu
      Probable reserves - 5.7 Mt @ 3.2% Cu
      Measured resources - 61 Mt @ 3.3% Cu
      Indicated resources - 8.1 Mt @ 2.7% Cu
      Inferred resources - 1 Mt @ 2% Cu
  500 orebody
      Inferred resources - 70 Mt @ 1% Cu
  Mt Isa copper open pit
      Measured resources, - 98 Mt @ 1.4% Cu
      Indicated resources - 69 Mt @ 1.2% Cu
      Inferred resources - 110 Mt @ 1% Cu

JORC compliant ore reserves and minerals resources (at 31 December 2011) were as follows (X-Strata 2012):
  X41 Mine, 1000 & 1900 orebodies
      Proved + probable reserves - 31 Mt @ 1.8% Cu
      Measured + indicated resources - 60 Mt @ 1.9% Cu
      Inferred resources - 8 Mt @ 2% Cu
  Enterprise Mine, 3000 & 3500 orebodies
      Proved + probable reserves - 24 Mt @ 3% Cu
      Measured + indicated resources - 45 Mt @ 3% Cu
      Inferred resources - 1 Mt @ 2% Cu
  500 orebody
      Inferred resources - depleted
  Mt Isa copper open pit
      Measured + indicated resources - 150 Mt @ 1.2% Cu
      Inferred resources - 133 Mt @ 1% Cu

The X41, Enterprise and 500 orebody mines are underground, block caving operations.   Mt Isa copper open pit exploits the upper sections of the silica-dolomite hosted copper orebody. The resource is based on a 0.5% Cu cut-off and comprises approximately 60% promary chalcopyrite, with the remainder is oxidised or partially oxidised with minor supergene chalcocite.

The mine is operated by X-Strata Copper.

The most recent source geological information used to prepare this decription was dated: 2007.     Record last updated: 31/12/2012
This description is a summary from published sources, the chief of which are listed below.
© Copyright Porter GeoConsultancy Pty Ltd.   Unauthorised copying, reproduction, storage or dissemination prohibited.

Mt Isa Copper

  References & Additional Information
   Selected References:
Andrew A S, Heinrich C A, Wilkins R W T, Patterson D J  1989 - Sulfur isotope systematics of Copper ore formation at Mount Isa, Australia: in    Econ. Geol.   v84 pp 1614-1626
Bell T H, Perkins W G, Swager C P  1988 - Structural controls on development and localization of syntectonic Copper mineralization at Mount Isa, Queensland: in    Econ. Geol.   v83 pp 69-85
Betts, P.G., Giles, D., Mark, G., Lister, G.S., Goleby, B.R. and Ailleres, L.,  2006 - Synthesis of the Proterozoic evolution of the Mt Isa Inlier: in    Australian J. of Earth Sciences   v.53, pp. 187-211.
Blaikie, T.N., Betts, P.G., Armit, R.J. and Ailleres, L.,  2017 - The ca. 1740-1710 Ma Leichhardt Event: Inversion of a continental rift and revision of the tectonic evolution of the North Australian Craton: in    Precambrian Research   v.292, pp. 75-92
Cave, B., Lilly, R. and Rea, P.,  2023 - In Situ U-Pb Monazite Geochronology Records Multiple Events at the Mount Isa Cu (±Zn-Pb-Ag) Deposit, Northern Australia: in    Econ. Geol.   v.118, pp. 225-236.
Conaghan, E.L., Hannan, K.W. and Tolman, J.  2003 - Mount Isa Cu and Pb-Zn-Ag deposits, NW Queensland Australia: in   Regolith Expression of Australian Ore Systems - A compilation of geochemical case histories and conceptual models CRC LEME online,   http://crcleme.org.au/RegExpOre/MtIsa.pdf, 3p.
Davis, T.P.,  2004 - Mine-Scale Structural Controls on the Mount Isa Zn-Pb-Ag and Cu Orebodies: in    Econ. Geol.   v.99, pp. 543-559.
Derrick G M  1996 - The geophysical approach to metallogeny of the Mt Isa Inlier - what sort of orebody do you want: in    Proc The AusIMM Annual Conference, Perth, 24-28 March, 1996 The AusIMM, Melbourne    pp 349-366
Gulson B L, Perkins W G, Mizon K J  1983 - Lead isotope studies bearing on the genesis of copper orebodies at Mount Isa, Queensland: in    Econ. Geol.   v78 pp 1466-1504
Heinrich C A, Bain J H C, Mernagh T P, Wyborn L A I, Andrew A S, Waring C L  1995 - Fluid and mass transfer during metabasalt alteration and Copper mineralization at Mount Isa, Australia: in    Econ. Geol.   v90 pp 705-730
Heinrich, C.A., Andrew, A.S., Wilkins, R.W.T. Patterson D J  1989 - A fluid inclusion and stable isotope study of synmetamorphic Copper ore formation at Mount Isa, Australia: in    Econ. Geol.   v.84, pp. 529-550.
Lilly, R., Taylor, D. and Spanswick, N.  2017 - Mount Isa Cu-Pb-Zn deposit including George Fisher: in Phillips, G.N., 2017 Australian Ore Deposits, The Australasian Institute of Mining and Metallurgy,   Mono 32, pp. 473-478.
Mathias B V, Clark G J  1975 - Mount Isa copper and silver-lead-zinc orebodies - Isa and Hilton mines: in Knight C L, (Ed.), 1975 Economic Geology of Australia & Papua New Guinea The AusIMM, Melbourne   Mono 5 pp 351-372
McGoldrick P J, Keays R R  1990 - Mount Isa Copper and Lead-Zinc-Silver ores: coincidence or cogenesis?: in    Econ. Geol.   v85 pp 641-650
McLellan, J.G., O Sullivan, R., Miller, B. and Taylor, D.,  2014 - Geomechanical Modelling of the Mount Isa Copper Deposit - Predicting Mineralisation: in   Ninth International Mining Geology Conference, Adelaide, S.A., 18-20 August, 2014, Mining geology through the value chain, The AusIMM and Australian Institute of Geoscientists,   Proceedings, pp. 197-205.
Painter, M.G.M., Golding, S.D., Hannan, K.W. and Neudert, M.K.,  1999 - Sedimentologic, petrographic, and Sulfur isotope constraints on fine-grained pyrite formation at Mount Isa mine and environs, northwest Queensland, Australia: in    Econ. Geol.   v.94, pp. 883-912.
Perkin W G  1984 - Mount Isa Silica Dolomite and Copper orebodies: the result of a syntectonic hyrothermal alteration system: in    Econ. Geol.   v79 pp 601-637
Perkins C, Heinrich C A, Wyborn L A I  1998 - 40Ar/39Ar geochronology of Copper mineralization and regional alteration, Mount Isa, Australia: in    Econ. Geol.   v94 pp 23-36
Perkins W G  1990 - Mount Isa copper orebodies: in Hughes FE (Ed.), 1990 Geology of the Mineral Deposits of Australia & Papua New Guinea The AusIMM, Melbourne   Mono 14, v1 pp 935-941
Polito, P.A., Kyser, T.K., Southgate, P.N. and Jackson, M.J.,  2006 - Sandstone Diagenesis in the Mount Isa Basin: An Isotopic and Fluid Inclusion Perspective in Relation to District-Wide Zn, Pb, and Cu Mineralization: in    Econ. Geol.   v.101, pp. 1159-1188.
Swager C P  1985 - Syndeformational Carbonate-replacement model for the Copper mineralization at Mount Isa, northwest Queensland, a microstructural study: in    Econ. Geol.   v80 pp 107-125
Wilde A R, Jones P A, Gessner K, Ailleres L, Gregory M J and Duncan R J,  2006 - A Geochemical Process Model for the Mount Isa Copper Orebodies : in    Econ. Geol.   v101 pp 1547-1567
Williams P J  1998 - An introduction to the metallogeny of the McArthur River-Mt Isa-Cloncurry Minerals Province: in    Econ. Geol.   v93 pp 1120-1131
Williams, B.J., Blenkinsop, T.G., Lilly, R., Thompson, M.P. and Ilaava, P.,  2023 - Foliation boudinage structures in the Mount Isa Cu system: in    Australian J. of Earth Sciences   v.69, 18p. doi:10.1080/08120099.2022.2153384

Porter GeoConsultancy Pty Ltd (PorterGeo) provides access to this database at no charge.   It is largely based on scientific papers and reports in the public domain, and was current when the sources consulted were published.   While PorterGeo endeavour to ensure the information was accurate at the time of compilation and subsequent updating, PorterGeo, its employees and servants:   i). do not warrant, or make any representation regarding the use, or results of the use of the information contained herein as to its correctness, accuracy, currency, or otherwise; and   ii). expressly disclaim all liability or responsibility to any person using the information or conclusions contained herein.

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