740km north-west of Adelaide, South Australia
Archean meta-sedimentary Christie Gneiss
702,570oz of gold
The Challenger gold mine is located in South Australia, approximately 740km north-west of Adelaide, and is owned and operated by Kingsgate Consolidated. The mine was discovered in 1995 and was developed in 2002 as an open pit operation. In 2005, the mine was successfully converted into an underground operation.
The mine was originally owned and operated by Dominion Mining. In February 2011, Kingsgate Consolidated acquired Dominion Mining and hence took over the management control.
An expansion project to increase the processing capacity of the mine by more than threefold is currently underway. On completion of the expansion by 2012, the total processing capacity will reach 530,000t a year.
The mine remained an undeveloped operation for years after Dominion discovered it in 1995.
In December 2000, Dominion purchased the 50% stake held by Resolute and began a feasibility study on the development of an open-cut mining operation. The study was completed in 2001.
Shortly after that, the company began construction and related infrastructure works. The plant was commissioned in September 2002 and on 24 October 2002 the first shipment of gold bullion was achieved.
The deposit is characterised by archean meta-sedimentary Christie Gneiss. Ores are hosted within feldspar–quartz–cordierite–garnet–biotite gneiss.
High-grade rough gold minerals are found in combination with slightly disseminated arsenopyrite, loellingite and pyrrhotite within and next to veins that bear coarse quartz, feldspar, garnet and bionite. Trace amounts of bismuth minerals, tellurides, chalcopyrite, pentlandite and sphalerite are also hosted within the deposit.
Four main ore positions are outlined in the deposit: the M1, M2, M3 lodes and the M1 shadow zone. More than 98% of gold underground is found in M1 and M2 lodes, and the M1 shadow zone. All lodes are open at depth. The orebody in M1 lode continues to a depth of 1,000m below surface.
Geology and reserves
Ores occur as high grade, narrow and partially parallel lodes that exist as connected dilational zones within an irregular fold system.
Well-structured shoots that plunge 30° towards the 055° local grid also host the ores. The internal veins are geometrically slanted towards the plunge azimuth of the shoots. The veins are characterised by consistent and elongated down plunge and short strike lengths.
The reserves of the mine are estimated at 702,570oz of gold. Approximately 940oz of gold is contained in circuit.
Mining and processing
To mine the orebody hosted in M1 lode, an optimum stope design was drafted in the last quarter of 2004 after testing two stopes above the 1020 level. Drilling and blasting techniques were adopted and that reduced mining dilution to stopes.
The M1 lode has been mined 700m below the surface. Stoping was completed at 600m of the M1 lode. During the same time, stoping progressed on the 400 and 380 levels of the M1 and M2 shoots.
The M2 shoot was also fully developed on the 840, 820 and 760 levels and partially developed between levels 540 to 600.
The ores are processed in a typical carbon-in-pulp (CIP) gold processing facility. The facility can process up to 425,000t of primary ore per year.
It includes a jaw crusher complete with a cone crusher, a ball mill, a gravity circuit that recollects hard-grained gold, cyanidation leaching and absorption circuit and conventional elution and electrowinning for producing gold bullion. The site also has a laboratory that uses leachwell equipment to rapidly assay drill samples.
The mine produced 98,755oz of gold during 2008-09. Approximately 430,798t of ore was mined and a total of 434,087t was processed. The ore was graded at 7.54g / t and the recovery rate was 94%.
As of June 2010, 647,205oz of gold was produced from the mine.
To increase processing capacity to 530,000t per year, an expansion of the mine’s processing unit is currently under way. The expansion, due for completion by December 2011, will boost gold production to 120,000oz per year from 98,755oz achieved in 2008-09. The contract for the extension was awarded to HWE Mining for a value of $202m.