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Highway, Reward |
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Queensland, Qld, Australia |
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Au Cu Ag
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Super Porphyry Cu and Au
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IOCG Deposits - 70 papers
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All papers now Open Access.
Available as Full Text for direct download or on request. |
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The Highway-Reward copper-gold-silver pipes are hosted by the Cambro-Ordovician Mount Windsor Volcanics some 32 km south of Charters Towers in north Queensland, Australia.
The Mount Windsor volcanic and sedimentary sequence forms a 165 km long east-west trending volcano-sedimentary belt from Ravenswood in the east to near Pentland in the west. It has been extensively intruded by the Ordovician to Permian composite Ravenswood Batholith and Lolworth Igneous Complex along its northern margin, and is overlain to the south by the extensive Tertiary alluvials and ferricretes of the Campaspe Beds.
The Mt Windsor Volcanics belong the the Seventy Mile Range Group which commences with a 9 km
thickness of Cambrian mixed volcanics and sediments dominated by continental-derived quartz and lithic rich sandstone, greywacke and siltstone. These are overlain by the 300 to 3500 m thick Cambrian Mount Windsor Formation comprising a sequence of rhyolitic volcanics with minor dacite and rare andesite, while sediments are only found at the base. The Mt Windsor Formation passes conformably upwards into the 500 to 4000 m thick Trooper Creek Formation made up of basaltic, andesitic, dacitic and rhyolitic lavas, intrusions and volcaniclastics, laminated siltstones and mudstones with local graptolites, calcareous meta-sediments, rare microbialites and thin ironstones.
All known volcanic associated massive sulphide deposits within the Mount Windsor Volcanics are hosted within the Trooper Creek Formation - these include Thalanga near the base, and Liontown and Hightway-Reward near the top of the unit.
The Trooper Creek Formation in turn passes up into the Ordovician Rollston Range Formation, the base of which is marked by the uppermost stratigraphic interval dominated by syneruptive volcaniclastics units and/or rhyolitic to basaltics lavas and synsedimentary intrusives. The Rollston Range Formation is a suite of volcanic and non-volcanic sediments up to 1 km thick.
The host sequence to Highway-Reward comprises a submarine, silicic, synsedimentary, intrusion dominated, volcanic succession which includes 13 porphyritic units within a 1x1x0.5 km volume. Rock relationships and textures suggest most of these rhyolites, rhyodacites and dacites originated as small, <350 m diameter synsedimentary sills and cryptodomes, separated by thin 0.2 to 30 m intervals of siltstone, sandstone, non-welded pumice breccia and polymictic lithic breccias, with very sparse evidence of eruptive magma.
The Highway and Reward pyrite-chalcopyrite pipes (which are 200 m apart) occur within, but close to the margins of intrusives, are discordant to local bedding, but include relict patches of rhyolite, rhodacite and peperite. There are 5 principal ore types, namely:
i). sub-vertical, pipe like bodies of massive pyrite-chalcopyrite, discordant to bedding, but parallel to D4, and associated with minor marginal discordant stratabound and disseminated sulphides
ii). sphalerite rich halos surrounding the massive sulphide pipes as around 500x225 m Zn-Pb-Ba rich zones of veins, veinlets, disseminations and stratabound massive sulphide pyrite-sphalerite-chalcopyrite-galena-barite in volcanic mass flow units in the hangingwall of the Reward pipe and discordant zones of semi-massive pyrite-sphalerite ±chalcopyrite ±quartz ±barite on the margins of the main pipes,
iii). footwall and hangingwall stringer zones of variably oriented planar to irregular pyrite ±quartz ±sericite stringer veins below and adjacent to the walls of the Reward and Highway pipes,
iv). gossanous zones near surface, and
v). underlying supergene mineralisation.
The Highway pipe is NE trending, 175 m long, and in its central and northern section splits into three separate pipes 3 to 10 m apart. It is composed of chalcopyrite rich massive pyrite.
The Reward pipe is composed of one main and and several smaller, sub-vertical, NNE trending massive pyrite pipes. The largest is 100x150m in plan and 250 m vertically, containing around 5 Mt of massive pyrite, including a small chalcopyrite rich zone.
The massive sulphides are enclosed within a halo of hydrothermal alteration extending over 150 m below the orebodies and 60 m above Highway, comprising and inner quartz-sericite ±pyrite interval, surrounded progressively by chlorite ±anhydrite/gypsum, chlorite-quartz-sericite and finally by chlorite-sericite.
Highway contained pre-mining reserves of 1.2 Mt @ 5.5% Cu, 1.2 g/t Au, 6.5 g/t Ag as primary ore and
0.07 Mt @ 6.04 g/t Au supergene ore.
Reward had pre-mining reserves 0.2 Mt @ 3.5% Cu, 1 g/t Au, 13 g/t Ag as primary ore
0.3 Mt @ 11.6% Cu, 1.8 g/t Au, 21 g/t Ag as supergene ore, and
0.1 Mt @ 6.9 g/t Au, 33 g/t Ag as oxide ore.
Between 1998 and 2005, 3.2 Mt @ 6.2% Cu, 1 g/t Au was mined from Highway-Reward and processed through the Thalanga Mill.
Highway-Reward District production and resources at the end of 2016 were (Beams et al., 2017):
Highway-Reward Copper - production, between 1995 and 2005 - 3.6 Mt @ 5.7% Cu.
Highway-Reward Oxide gold - production, between 1987 and 1995 - 0.26 Mt @ 4.47 g/t Au.
Highway-Reward-Conviction - Resources at December 2016 - 4.092 Mt @ 5.4% Cu, 0.5 to 1.0 g/t Au.
For detail see the reference(s) listed below.
The most recent source geological information used to prepare this decription was dated: 1999.
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.
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Beams S D, Laurie J P, O Neill D M 1990 - Reward polymetallic sulphide deposit: in Hughes F E (Ed.), 1990 Geology of the Mineral Deposits of Australia & Papua New Guinea The AusIMM, Melbourne Mono 14, v2 pp 1539-1543
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Beams, S.D., Bates, T.,Huston, D.L. and Morrison, I.J., 2017 - Polymetallic massive sulfide deposits of the Mount Windsor Subprovince: in Phillips, G.N., (Ed.), 2017 Australian Ore Deposits, The Australasian Institute of Mining and Metallurgy, Mono 32, pp. 689-692
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Berry R F, Huston D L, Stolz A J, Hill A P, Beams S D, Kuronen U, Taube A 1992 - Stratigraphy, structure, and volcanic-hosted mineralization of the Mount Windsor Subprovince, North Queensland, Australia: in Econ. Geol. v87 pp 739-763
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Doyle M G, Huston D L 1999 - The subsea-floor replacement origin of the Ordovician Highway-Reward volcanic-associated massive Sulfide deposit, Mount Windsor subprovince, Australia: in Econ. Geol. v94 pp 825-844
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Large R R, McPhie J, Gemmell J B, Herrmann W, Davidson G J 2001 - The spectrum of ore deposit types, volcanic environments, alteration halos, and related exploration vectors in submarine volcanic successions: some examples in Australia: in Econ. Geol. v96 pp 913-938
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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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