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Waterloo

Queensland, Qld, Australia

Main commodities: Cu Zn Pb Ag
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The Waterloo massive sulphide (VHMS) Cu-Zn-Pb deposit occurs in the Cambro-Ordovician Seventy Mile Range Group in northern Queensland, Australia and is approximately 30 km SW of Charters Towers.

It consists of several small, dismembered, stratabound, blanket-like, pyrite-chalcopyrite-sphalerite-galena massive sulphide lenses hosted by intensely altered volcanic rocks. The deposit and its host rocks have been deformed by regional Middle to Late Ordovician deformation and were affected by two subsequent events of brittle deformation.

The deposit was formed on top of a lava-dominated andesite succession comprising coherent volcanic units and related juvenile volcaniclastic rocks within a submarine volcanic and sedimentary succession that formed as a result of Cambro-Ordovician back-arc volcanism at the northern end of the Tasman fold belt system of eastern Australia. The host Seventy Mile Range Group is known for a number of volcanic-hosted massive sulphide (VHMS) deposits, including two significant (Thalanga and Highway-Reward) and several smaller deposits (e.g., Liontown) in the Charters Towers district.

The Seventy Mile Range Group is an approximately east-west trending and sub-vertically dipping belt that outcrops discontinuously over a distance of some 165 km and has an apparent stratigraphic thickness of approximately 12 000 m. The group has been intruded along its northern margin by Ordovician to Devonian granitoids and gabbroic intrusions and is partially concealed beneath younger sedimentary rocks and occurs on the south facing limb of an east-west trending syncline.

The Seventy Mile Range Group consists of four conformable stratigraphic units, namely, from the base:
i). The lowermost Puddler Creek Formation comprises a thick (up to 9000 m), largely continent-derived volcanic and sedimentary package that is dominated by quartz and lithic sandstone, feldspar-quartz-lithic sandstone, and siltstone. Subordinate basaltic to intermediate volcanic units comprise the upper 500 to 200 m represent the precursors of the overlying Mount Windsor Formation.
ii). The Mount Windsor Formation (up to 3500 m thick) consists of massive coherent rhyolite and autoclastic breccia that formed domes and lava flows (commonly 100 to 150 m thick), with minor associated volcaniclastic rocks, and rare dacitic to andesitic lava flows. The unit is locally intruded by mafic sills and dykes.
iii). The overlying Trooper Creek Formation (500 m in the west, up to 4000 m thick in the centre) comprises basaltic to rhyolitic lavas, synvolcanic intrusions, and associated volcaniclastic rocks, as well as a relatively thick succession of well-bedded mudstone and calcareous metasedimentary strata. This unit is the host to the majority of the VHMS deposits of the Charters Towers district.
iv). The Rollston Range Formation (up to 1000 m thick) represents the uppermost part of the Seventy Mile Range Group and consists of sandstone and mudstone of mixed volcanic and non-volcanic provenance but generally lacks coherent volcanic units although dacitic lavas occur locally.

The dismembered, blanket-like, pyrite-chalcopyrite-sphalerite-galena massive sulphide lenses are located at or near the sub-vertical contact between intensely altered and schistose rocks and a coarse volcaniclastic unit. The intensely altered rocks in the footwall of the mineralisation are underlain by relatively unaltered massive and vesicular andesite. Hydrothermal activity responsible for the deposition of massive sulphides appears to have commenced during the waning stages or after the cessation of this andesite volcanism. The coarse volcaniclastic rocks in the immediate hanging wall of the massive sulphide lenses host a coherent dacite unit. The upper part of the Waterloo host succession consists of mudstone, fine- to coarse-grained volcaniclastic rocks and massive units of basaltic to andesitic compositions. The intense hydrothermally altered footwall rocks to the massive sulphide lenses ends abruptly 700 m to the east, along strike from the Waterloo deposit. Distal barite lenses at the Agincourt prospect, and a disseminated sulphide-rich zone at the Windsor Creek prospect, are found along strike to the west, while hydrothermal alteration in the footwall of the sulphide and barite mineralisation finishes abruptly 1.5 km to the west of the Waterloo deposit.

The massive sulphide lenses are confined to a relatively thin stratigraphic interval which typically overlies silicic-altered volcanic rocks. Locally, strongly altered rocks showing rare relict volcanic textures suggest a coarse volcaniclastic precursor in the immediate footwall to the massive sulphide that is texturally similar to the volcaniclastic rocks of the hanging wall. The immediate hanging wall to the massive sulphide bodies consists of pyrite- and white mica-rich (phyllic alteration facies), intensely foliated rocks lacking relict volcanic textures. The intensity of the hydrothermal alteration diminishes rapidly upward, with the upper limit of the favourable horizon being defined by the first occurrence of rocks showing abundant relict volcanic textures. The hanging wall to the massive sulphide is dominated by variably altered, coarse quartz-feldspar crystal-rich sandstone and breccia that defines a discrete marker horizon.

The stratabound mineralisation has been interpreted to have formed largely at or very close to the sea floor in a moderately deep to deep marine environment. Formation of the massive sulphides was accompanied by mass-flow deposition of coarse quartz-feldspar crystal-rich volcanic debris that records broadly contemporaneous, probably explosive, rhyolitic volcanism occurring outside the immediate deposit area.

The deposit consists of several dismembered, blanket-like massive sulphide lenses that together comprise a total resource of 0.2435 Mt @ 3.8% Cu, 13.8% Zn, 3.0% Pb, 74 g/t Ag (Monecke et al., 2006).

Published resources in 2012 (Kagara Mining, 2012) were:
    Inferred Oxide ore - 0.055 Mt @ 0.1% Zn, 2.3% Pb, 0.2% Cu, 3.7 g/t Au, 15 g/t Ag;
    Indicated transition ore - 0.097 Mt @ 14.5% Zn, 2.4% Pb, 3.2% Cu, 1.6 g/t Au, 78 g/t Ag;
    Inferred transition ore - 0.069 Mt @ 6.4% Zn, 1.1% Pb, 0.8% Cu, 0.4 g/t Au, 24 g/t Ag;
    Indicated sulphide ore - 0.309 Mt @ 13.0% Zn, 2.0% Pb, 2.5% Cu, 1.3 g/t Au, 65 g/t Ag;
    Inferred sulphide ore - 0.232 Mt @ 8.3% Zn, 0.8% Pb, 0.9% Cu, 0.4 g/t Au, 28 g/t Ag;
    TOTAL tonnage of ore - 0.762 Mt.

The most recent source geological information used to prepare this summary was dated: 2006.     Record last updated: 24/6/2013
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.


  References & Additional Information
 References to this deposit in the PGC Literature Collection:
Monecke T, Gemmell J B, and Herzig P M,  2006 - Geology and Volcanic Facies Architecture of the Lower Ordovician Waterloo Massive Sufide Deposit, Australia: in    Econ. Geol.   v101 pp 179-197


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