OzTour '99 - Key Australian Base Metal & Gold Deposits

Deposits were visited and workshops presented in the following order:

Adelaide Briefing

"Tectonic, Geologic & Metallogenic Framework of South Australia", covering the tectonic and geologic framework of South Australia, the distribution of significant mineralisation and the regional setting of the Olympic Dam deposit. This was presented by geologists of Primary Industries and Resources South Australia (PIRSA).

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Olympic Dam Cu-U-Au - South Australia

The Olympic Dam ore deposit lies within the outer margins of the Lower Proterozoic Gawler Craton in northern South Australia. It falls within the Stuart Shelf where 300刞 of flat lying, barren, Upper Proterozoic to lower Paleozoic sediments unconformably overlie both the craton and the ore deposit. Mineralisation is hosted by the Olympic Dam Breccia Complex which is developed within the Mid Proterozoic (1600-1585 Ma) Roxby Downs Granite. The Olympic Dam Breccia Complex comprises a downward narrowing funnel shaped body of fractured, brecciated and hydrothermally altered granite which has resulted in a great variety of granitic, hematitic and siliceous breccias. The outer margins of the complex are diffuse, grading outwards from heterolithic breccia, through granite breccia, to crackle breccia to fractured granite. Minor volcaniclastics are found in diatreme structures at the top of the complex. The resource occurs as up to 150 separated bodies distributed within an annular zone up to 4 km in diameter surrounding the central barren hematite-quartz breccia. The highest grade mineralisation occurs within an up to 40 m thick, shallowly inward dipping, irregularly developed, chalcocite-bornite 'layer', where it cuts hematite rich breccia zones. This undulose layer grades down and outwards into chalcopyrite and then pyrite rich zones. As at June 1997 Proven reserves totalled 82 Mt @ 2.4% Cu, 0.6 g/t Au, 0.7 kg/t Uranium oxide; Probable reserve of 484 Mt @ 2.0% Cu, 0.7 g/t Au, 0.6 kg/t Uranium oxide; and Inferred resource of 1620 Mt @ 1.1% Cu, 0.4 g/t Au, 0.4 kg/t Uranium oxide. The current expansion should result in an annual production rate of 200 000 t of contained copper. The operation is owned by WMC Limited - 100%.

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Mt Keith disseminated Ni - Western Australia

The Mount Keith orebody is one of the worlds largest low grade, economic, disseminated nickel sulphide deposits. It lies within the regional Archaean Norseman-Wiluna greenstone belt, which is 13 km wide at this point and includes several ultramafic bodies. Mt Keith is near the centre of the greenstone belt and is hosted by a very large, layered body of olivine cumulate, which is believed to have formed within an extrusive komatiite. Nickel mineralisation extends for over 2 km of strike length and continues steeply down dip to a depth of at least 500 m. The mineralised ultramafic unit is up to 650 m thick, with ore grade mineralisation being developed over 250 to 300 m of this thickness. Pentlandite is the predominant Ni sulphide, accompanied by pyrrhotite and magnetite, and lesser millerite. At June 1996 the Measured, Indicated and Inferred Resource totalled 459 Mt @ 0.60% Ni. The operation treats around 10.5 Mt of ore per annum for 42 000 t Ni. The operation is owned by WMC Limited - 100%.

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Bronzewing primary & laterite Au - Western Australia

Bronzewing is located within the Yandal belt of deposits, 400 km north of Kalgoorlie. This belt, which lies on the eastern margin of the Archaean Norseman-Wiluna greenstone belt, contains five significant gold deposits, all found within the 1990's. The sequence in the belt varies along strike, containing interlayered tholeiitic and high Mg basalts, Fe rich shales, ultramafic rocks and internal granites, with felsic rocks to the south and ironstones to the north. The main structure, which comprises anastomosing highly strained rocks enclosing lenses of lower strain material, is 100 to 500 m wide at Bronzewing. Alteration associated with gold mineralisation includes calcite and ankerite in mafic rocks, and talc with dolomite-magnesite in ultramafic lithologies. Gold is hosted in 1 to 2 m thick laminated quartz veins and stockwork quartz veins and altered basalt wallrock, with the better grade in the veins. Pyrite is the predominant sulphide. The orebodies are covered by up to 50 m of young transported material and a thick lateritic profile. Economic grades of gold were associated with ferruginous pisolites in the lateritic profile and were exploited early in the mine life, although not a major contributor to overall production. Their main contribution has been as an exploration indicator. The total resource in 1996 was 38.3 Mt @ 2.9 g/t Au, with total production to that date having been 12.6 Mt. Bronzewing is operated by Great Central Mines - 100%

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Murrin Murrin silicate laterite Ni - Western Australia

The Murrin Murrin group of deposits overlie the Archaean Norseman-Wiluna greenstone belt. Lateritisation of extensive ultramafic sequences in the Murrin Murrin district has resulted in enrichment of nickel and cobalt within limonite and nontronite clays in at least 10 zones. The deposits overlie serpentinised Archaean, medium to coarse grained olivine cumulate peridotites of komatiitic origin near the centre of the greenstone belt. The lateritic profile passes upwards from the unweathered ultra-mafic, through mixed saprolite and ultramafic, to siliceous saprolite, saprolite, ferruginous saprolite, smectite, ferruginous smectite, to the upper ferruginous zone. The Ni-Co mineralisation, as indicated by the 0.5% Ni cutoff, is primarily confined to the smectite, saprolite and ferruginous smectite zones, and may be up to 25 m thick below the ferruginous zone. The total resource is 142.5 Mt @ 1.01% Ni, 0.06% Co. It will be treated by acid pressure leach hydrogen reduction autoclave technology at a rate of 3.75 Mtpa to produce 45 000 t of Ni and 3000 t of Co. The stage 2 expansion will produce up to 70 000 tpa Ni. The Murrin Murrin operation is owned by Anaconda Nickel Ltd 60%, and Glencore International AG 40%.

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Kambalda massive sulphide Ni-Cu - Western Australia

The Kambalda nickel mines lie within the Archaean Norseman-Wiluna greenstone belt, 70 km SSE of Kalgoorlie. Ore occurs as elongate, ribbon like, lens shaped bodies, situated within a komatiitic pile, and are located either at, or near the base of a sill like ultra-mafic unit which lies more or less conformably between two meta-basalt formations. A large granite stock lies at the centre of the Kambalda Dome around which the individual deposits are distributed, with peripheral porphyry dykes cutting both the hosts and ore. The orebodies grade upwards from the basal massive (>80%) sulphides, to matrix (40 to 80%) sulphide, to disseminated sulphides. Production has come from a series of separate orebodies or 'shoots'. Pentlandite is the principal Ni sulphide, accompanied by varying amounts of pyrrhotite, pyrite, chalcopyrite, chromite and magnetite. Lesser millerite zones are also present. Mining commenced in 1967, and from 1972 to 1988 exploration maintained resources at an almost constant level of around 25 Mt @ 3.2% Ni, with production in 1988 of 1.2 Mt of ore @ 2.96% Ni, 0.21% Cu for 34 140 t of Ni. In 1997 proven and probable reserves totalled 10.5 Mt while resources amounted to more than 20 Mt of comparable grades, with an output of 32 391 t of Ni in the previous 12 months. The operation is owned by WMC Limited - 100%.

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Traverse across the Norseman-Wiluna Greenstone Belt. - Western Australia

This traverse allows an overview of the stratigraphy and lithologies of this important greenstone belt which hosts many of the more important gold and nickel deposits of the Yilgarn Craton. It also allows and appreciation of the degree of exposure and weathering experienced over the Yilgarn Craton. The traverse will be conducted by geologists of the Western Australian Geological Survey.

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Kalgoorlie Super Pit primary Au - Western Australia

The Kalgoorlie Super Pit exploits the Golden Mile string of deposits which have yielded around 1200 t Au to the present. The Kalgoorlie gold field is developed within the Archaean Norseman-Wiluna greenstone belt of the Yilgarn Craton. The ore is controlled by a complex series of shears and is hosted within the Golden Mile Dolerite and to a lesser extent the Paringa Basalt. The ores are mineralogically refractory and complex, containing free gold and a significant proportion of gold- and silver-bearing telluride minerals, often intimately associated with pyrite. The mineralisation is localised within lodes that occur as alteration zones of ankerite+quartz+sericite+pyrite±telluride. The lodes are subdivided into the Eastern and Western Lode System on the flanks of the Kalgoorlie Syncline. Individual lodes occupy 20 to 50% of a lode channel and may be 30 to 1800 m long, 0.1 to 10 m thick and extend 30 to 1160 metres down dip. A further 800 t Au remains. The Super Pit operation is owned by KCGM - 100%, a JV between Normandy Mining and Homestake Australia.

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Cawse oxide laterite Ni - Western Australia

The Cawse project area comprises a corridor up to 500 m wide that extends for up to 25 km containing lateritic nickel and cobalt mineralisation. Around 80% of the mineralisation in the main Cawse Central tenements consists of a shallow, flat lying zone associated with limonitic clays in the upper 40 m of the weathering profile. A distinctive interval of high grade cobalt is located at the top of the limonite zone. A deeper nontronitic clay and talc zone is associated with bedrock structures. Mineralisation is associated with a structure cutting the Siberia Komatiite within the Archaean Norseman-Wiluna greenstone belt, 25 km to the north of Kalgoorlie. In 1997 the total resource amounted to 213 Mt @ 0.7% Ni, 0.04% Co, with a proven+probable reserve of 30.3 Mt. The ore deposit is an oxide laterite. The operation is operated by Centaur Mining & Exploration Ltd.

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Perth Seminar/Workshop "Archaean Geology & Mineralisation in WA"

The workshop will include presentations covering the following topics:

Geological and Tectonic Framework of Western Australia, with Particular Emphasis on the Archaean Cratons - Dr John Myers, GSWA.
The Distribution, Styles and Controls of the Archaean Gold and Coper-Zinc Mineralisation in Western Australia - Professor David Groves, University of WA.
The Distribution, Styles and Controls of Nickel Mineralisation in the Yilgarn Craton Rob Hill, CSIRO.
Evolution of the Regolith Stratigraphy of the Yilgarn Craton and Lateritic Deposits - CRC-LEME.
The Behaviour of Base and Precious Metals in the Weathering Profile - CRC-LEME..

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Golden Grove Cu-Zn-Ag-Au - Western Australia

Scuddles is the most significant Archaean volcanic hosted massive sulphide deposit in Australia. It occurs within the Yalgoo greenstone belt of the Murchison Province, which is in turn part of the Archaean Yilgarn Craton. The greenstone belt is characterised by heterogeneous deformation, with narrow zones of high strain, separating weakly deformed domains. The deposit occurs within a 1000 to 3000 m thick sequence dominated by felsic and intermediate volcaniclastic sediments, lavas and associated autoclastic breccias. Many later dolerite and gabbro dykes infilled extensional fractures. The ore deposit is over 600 m long and up to 50 m thick, occurring as two steeply west dipping lenses of massive sulphides. The massive sulphides occur as three types, namely massive (>50%) sphalerite at the top, massive pyrite (<50% sphalerite, <5% chalcopyrite) and copper rich massive sulphides (>5% chalcopyrite). Immediately in the footwall of the massive sulphides is a zone of stockwork pyrite-chalcopyrite associated with silicification and chloritic alteration. The orebody is also accompanied by a halo of sericite, quartz, chlorite and carbonates. The sulphides have been dated at 2730±20 Ma. The pre-mining resource totalled 10.5 Mt @ 11.7% Zn, 0.8% Pb, 1.2% Cu, 89 g/t Ag, 1.1 g/t Au. Current total reserves + resources of mineable or potentially mineable ore/mineralisation in different grade classifications is near 25 Mt. The operation is owned by Normandy Mining Ltd - 100%.

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		An AMF-PGC International Study Tour Developed & Managed by Porter GeoConsultancy OzTour '99 Key Australian Base Metal and Gold Deposits 9-29 May, 1999 - In Two Separate Modules
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