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Dugald River
Queensland, Qld, Australia
Main commodities: Zn Pb Ag

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The Dugald River zinc-lead-silver deposit is located in the Mt Isa Inlier, ~65 kilometres NW of Cloncurry and ~90 km NE of Mount Isa in northwest Queensland, Australia (#Location: 20° 14' 54"S, 140° 9' 18"E).

The Dugald River deposit is interpreted to be a structurally controlled ore shoot within a larger, tabular lode which is broadly conformable with the sediments of the Corella Formation. The broader sequence hosting the orebody comprises a thick package of variably carbonatic argillitic and silici-clastic sediments comprising calc-silicates, black graphitic slate, argillaceous limestone and quartzites of the Corella Formation, Lady Clayre Dolomite and the Knapdale Quartzite. The immediate host is the Dugald River Slate of the Corella Formation.

The tabular Dugald River lode has a strike length of some 2200 m and down dip extent of at least 1000 m, and ranges in thickness from 5 to more than 30 m. This lode is not parallel to bedding, ie. it is transgressive, by as much as 15 m across the sequence in a distance along the lode of 100 m, although at depth it appears to approach the lithological banding. The lode has a reasonably constant strike, while the bedding varies by up to 60°. The mineralised lode is banded over the majority of its strike length with grades usually of <10% Zn equivalent over an average width of 5 m. The majority of the strike length of this lower grade mineralisation occurs as two wings on either side, of a central thicker (up to more than 30 m), steeply plunging, brecciated zone which contains the higher grade 'economic' ore shoots. Higher grade zones within the ore shoots are found adjacent to zones of shearing which cut the lode. There are a number of types of ore breccia, including the following, in order of decreasing grade:

Massive breccia - mechanically rounded shale & siliceous clasts from 3 to 10 mm in diameter ranging from shale to siliceous fragments with similar rounded pyrrhotite &/or pyrite, all set in a matrix of massive fine sphalerite; this breccia has the highest grade.
Pyrrhotite breccia - ragged, slaty clasts in a pyrrhotite rich ore sulphide matrix. On the margins of the clasts pyrrhotite can be seen invading cracks and fractures in the slate clasts, forming more and smaller clasts.
Slaty breccia - ragged, wavy and 'fish hook' slaty clasts set in a matrix of pyrite, sphalerite & lesser galena.
Quartz breccia - similar to massive breccia, but with a siliceous matrix; this is the lowest grade.

These brecciated ore types appear to represent "durchbewegung" textures common to structurally modified/controlled sulphide orebodies.

The published total resource in 1994 (CRA Limited) was 38.5 Mt @ 13% Zn, 2.1% Pb, 42g/t Ag.

Resources at 30 June, 2015 (prior to mining) were as follows (MMG Limited Reserves and Resources statement):
  Primary zinc
      Measured resource - 5.7 Mt @ 14.5% Zn, 2.0% Pb, 63 g/t Ag,
      Indicated resource - 25.9 Mt @ 13.% Zn, 2.2% Pb, 51 g/t Ag,
      Inferred resource - 25.7 Mt @ 12.7% Zn, 1.8% Pb, 13 g/t Ag,
      TOTAL resource - 57.3 Mt @ 13.2% Zn, 2.0% Pb, 35 g/t Ag,
  Primary copper
      Inferred resource - 4.4 Mt @ 1.8% Cu, 0.2 g/t Au.

Remaining Mineral Resources at 30 June, 2018 were as follows (MMG Limited 2018 Reserves and Resources statement) at a cut-off of AUD 146/t Nett Smelter Return and are inclusive of Ore Reserves:
  Primary zinc
      Measured resource - 8.9 Mt @ 12.9% Zn, 2.3% Pb, 72 g/t Ag,
      Indicated resource - 24.3 Mt @ 12.6% Zn, 2.0% Pb, 30 g/t Ag,
      Inferred resource - 23.5 Mt @ 12.1% Zn, 1.5% Pb, 8 g/t Ag,
      TOTAL resource - 56.7 Mt @ 12.4% Zn, 1.8% Pb, 27 g/t Ag,
  Primary copper
      Inferred resource - 6.6 Mt @ 1.5% Cu, 0.2 g/t Au at a cutoff of 1% Cu.
Remaining Ore Reserves at 30 June, 2018 were as follows (MMG Limited 2018 Reserves and Resources statement):
      Proved reserves - 6.9 Mt @ 11.5% Zn, 2.1% Pb, 65 g/t Ag,
      Probable reserves - 21.7 Mt @ 11.7% Zn, 2.0% Pb, 30 g/t Ag,
      TOTAL reserves - 28.6 Mt @ 11.7% Zn, 2.0% Pb, 38 g/t Ag,

The most recent source geological information used to prepare this decription was dated: 2000.    
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.

Dugald River

  References & Additional Information
   Selected References:
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.
Broome, J. and Corley, D.,  2017 - Dugald River Zn-Pb-Ag deposit: in Phillips, G.N., 2017 Australian Ore Deposits, The Australasian Institute of Mining and Metallurgy,   Mono 32, pp. 493-496.
Connor A G, Johnson I R, Muir M D  1990 - Dugald River Zinc-Lead deposit: in Hughes F E (Ed.), 1990 Geology of the Mineral Deposits of Australia & Papua New Guinea The AusIMM, Melbourne   Mono 14, v1 pp 949-953
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
Foster, D.R.W. and Austin, J.R.,  2008 - The 1800-1610 Ma stratigraphic and magmatic history of the Eastern Succession, Mount Isa Inlier, and correlations with adjacent Paleoproterozoic terranes: in    Precambrian Research   v.163, pp. 7-30.
Gibson, G.M., Hutton, L.J. and Holzschuh, J.,  2017 - Basin inversion and supercontinent assembly as drivers of sediment-hosted Pb-Zn mineralization in the Mount Isa region, northern Australia: in    Journal of the Geological Society   v.174, pp. 773-786.
Whitcher I G  1975 - Dugald River zinc-lead lode: in Knight C L, (Ed.), 1975 Economic Geology of Australia & Papua New Guinea The AusIMM, Melbourne   Mono 5 pp 372-376
Xu G  1996 - Structural geology of the Dugald River Zn-Pb-Ag deposit, Mount Isa Inlier, Australia: in    Ore Geology Reviews   v11 pp 339-361
Xu G  1998 - A fluid inclusion study of syntectonic Zn-Pb-Ag mineralization at Dugald River, northwest Queensland, Australia: in    Econ. Geol.   v93 pp 1165-1179
Xu G,  1997 - Microstructural evidence for an epigenetic origin of a Proterozoic zinc-lead-silver deposit, Dugald River, Mount Isa Inlier, Australia : in    Mineralium Deposita   v32 pp 58-69

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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