The Australia's largest open cut gold mine
Location: Kalgoorlie, Western Australia.
Products: Gold.
Owner: Kalgoorlie Consolidated Gold Mines Pty Ltd.
Overview: The Super Pit is located off the Goldfields Highway on the south-east edge of Kalgoorlie, Western Australia. The pit is oblong in shape and is approximately 3.5 kilometres long, 1.5 kilometres wide and 570 metres deep. At these dimensions, it is large enough to be seen from space.
The Super Pit is owned by Kalgoorlie Consolidated Gold Mines Pty Ltd, a company owned 50/50 by Barrick Gold Corporation and Newmont Mining Corporation. The mine produces 850,000 ounces (28 tonnes) of gold per year, and employs around 550 employees directly on site.
Originally consisting of a number of small underground mines, consolidation into a single open pit mine was attempted by Alan Bond, but he was unable to complete the takeover. The Super Pit was eventually created in 1989 by Kalgoorlie Consolidated Gold Mines Pty Ltd.
Barrick Gold acquired its share of the mine in December 2001, when it took over Homestake Mining Company. Newmont became part-owner of the mine three months later, when it acquired Normandy Mining in February 2002.
Geological Setting: Most of the good gold mined in the Super Pit occurs within ore lodes formed by ancient shears in a rock unit called the Golden Mile Dolerite. The gold mining area of Kalgoorlie-Boulder-Fimiston has long been called the Golden Mile because of the geographical concentration of rich mines in that area, even though the lodes occur in an area over 2 km in width and 1 km in depth.
Kalgoorlie Terrane.
1. Pre- to syn-D, granitoids were emplaced as broadly conformable sheet-like bodies at the base of, or within, the greenstone succession, probably during
2. Post-D, to syn-D, granitoids were diapirically emplaced, and are concentrated in a zone along the western side of the Kalgoorlie Terrane.
3. Late-tectonic to post-tectonic granitoids were emplaced late in the history of the Terrane. Limited geochronological data suggest the granitoids were emplaced at 2690-2680 Ma (group I), 2665-2660 Ma (group 2) and 2650-2600 Ma (group 3) (Hill ef al.,
1992). Small porphyry intrusions, including lamprophyres
(Rock et aL, 1989), are widespread and petrologically diverse; they may be genetically related to some of the I-type granitoid suites (Witt, 1992). They are common in and near regional deformation zones, and are associated with many gold deposits (Perring et al., 1988,1989).
GOLD MINERALIZATION:
All rock types in the Kalgoorlie Terrane host gold mineralization, but most production has come from fractionated quartz-dolerite zones of mafic-ultramafic sills and from tholeiitic basalt.
The dominance of quartz-dolerite and tholeiitic basalt remains even if bias introduced by the "giant" Kalgoorlie deposits (Golden
Mile, Mount Charlotte) is eliminated. A similar picture emerges when host rocks to gold mineralization throughout the Yilgarn Craton are considered (.1B; Groves & Barley, 1988). Quartz-dolerite and tholeiitic basalt host rocks are characterized by high FeO* contents and FeO*/(FeO*+MgO) (Tables II.1,11.2), where FeO* is total iron expressed as FeO. Although mafic rocks are the dominant hosts, other rock types (e.g., granitoids, porphyry, ultramafic rocks) host important deposits, and can even be the dominant host rock on a camp scale (e.g., porphyries at New Celebration). All rock types in the Kalgoorlie Terrane host gold mineralization, but most production has come from fractionated quartz-dolerite zones of mafic-ultramafic sills and from tholeiitic basalt .
Production:
Mining is via conventional drill and blast mining via face shovels and dump trucks. Around 15 million tonnes of rock is moved in any given year, consisting primarily of waste rock.
Gold within the Golden Mile lode system is unusual in that it is present as telluride minerals within pyrite. In order to recover the gold, the ore must be crushed, passed through a gravity circuit to recover the free gold present in some of the higher-grade lodes, and then subjected to flotation to produce an auriferous pyrite concentrate. This is then roasted at a small smelter outside Kalgoorlie-Boulder to liberate the gold from the tellurides, with doré bars poured.
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