Overview
Northparkes Mines is a copper-gold mine, situated 27 kilometres north/north-west of the town of Parkes in Central West New South Wales. The mine is a joint venture between Rio Tinto (80%) and the Sumitomo Group (20%). It produces high grade copper-gold concentrate, which is shipped to international smelters. The mine was the first in Australia to use the block cave mining method.
Location
Northparkes Mines is a copper-gold mine located at Goonumbla, approximately 27 kilometres north-north-west of the town of Parkes in Central West NSW, Australia.
The majority of the mines employees and their families live in Parkes, a country town of 10,000 inhabitants. The town has excellent health, education and sporting facilities. It is within easy reach of the larger towns of Orange and Dubbo and the Parkes airport is linked with three flights per day to Sydney. The 365km journey takes approximately one hour.
Geology
The deposits at Northparkes Mines occur in a geological province known as the Lachlan Fold Belt (LFB). The LFB includes most of the western and south eastern parts of NSW and extends into Victoria. They belong to a broad class of deposits called porphyry copper-gold deposits. These occur throughout the world and include the largest copper mines in the world, such as those in Chile and Indonesia.
The copper occurs predominantly as the sulphide minerals bornite (Cu5FeS4) and chalcopyrite (CuFeS2) occurring on fractures or in veins with quartz (SiO2). Copper contents typically range from approximately 0.5 to 1.5 per cent. Gold occurs as very fi ne grains (not normally visible to the naked eye) within the sulphide minerals and typically ranges from 0.3 to 1 gram of gold per tonne of ore.
Mining & Operations
Northparkes development was staged with initial production in November 1993 from the E22 and E27 open pits and later from the E26 underground block cave mine in 1996. The ore processing plant comprised two modules and began treating oxide ore from E22 and E27 in April 1994, oxide ore was exhausted from the open cuts in 1997.
In October 1993 construction of the E26 underground block cave mine, Australia's first, commenced. In 1997 Lift 1 reached design production of 3.9 Mtpa and become the world's most productive underground hard rock mine, producing 42,600 tonnes of ore per underground employee year (including contractors). Productivity peaked in 2000, reaching over 50,000t per employee.
Northparkes commissioned its second block cave mine, E26 Lift 2 in 2004 and an extension, E26 Lift 2 North, in 2008. In 2006 Northparkes commenced construction of E48 Lift 1, its third major block cave mine, with full production expected to be achieved in late 2010. E48 extends the life of Northparkes' operations until 2024.
In 2009 the E27 pit was granted approval to commence in-pit tailings, which is the disposal of tailings from the ore processing facility to fill the void left from the previous mining campaign. This ensures that post mining the void would no longer exist and rehabilitation of the area would be able to proceed.
Current Mining campaign of the E22 Open CutThe E22 pit was reopened in 2007 to supplement production during the construction of the underground block cave mines E26 Lift 2North and the E48 project.
Mining is being undertaken with a fleet comprising one 300 tonne primary excavator, one 120 tonne secondary excavator and twelve 100 tonne Caterpillar 777D trucks with ancillary support equipment including dozers, graders and water carts.
Processing
Crushed Ore Handling
There are two coarse ore stockpiles receiving material from the surface and underground crushers. The total capacity of each stockpile is 150,000 tonnes. Crushed ore is reclaimed by four vibrating feeders under each stockpile.
Grinding
The grinding circuit is comprised of two separate modules, each incorporating a Semi Autogenous Grinding (SAG) mill, oversize crushing technology, two stages of ball milling and flash flotation.
Flotation
Flotation takes place in two parallel modules, each linked to its own grinding circuit. The flotation process aims to float a sulphide concentrate to recover the major copper and gold bearing minerals. (The circuits consist of pre-float, rougher, scavenger, cleaner, cleaner-scavenger and re-cleaner treatment stages).
The final concentrate produced for each module assays 34-36 per cent copper and is pumped to a concentrate thickener. Final tailings from each module are pumped to a tails thickener for dewatering
Concentrate Thickening and Filtration
Final concentrate from the flotation circuits is pumped to thickeners where it is thickened to an average underflow density of 60 per cent solids. Thickened concentrate is then pumped to concentrate storage tanks prior to treatment through the filtration circuit, using ceramic disc filters.
The filtered concentrate is discharged onto slow moving conveyor belts, each equipped with a weightometer to determine final production of concentrate. The concentrate is conveyed into a storage shed before loading and transporting to customers.
Concentrate Handling
Concentrate is removed from the storage bays using a front-end loader, which loads concentrate into shipping containers carried on a semi-trailer. The containers are sealed and trucked to the Goonumbla rail siding 12km from the concentrator. The full containers are loaded onto trains, with the carrying capacity of each train up to 60 containers. Concentrate is railed to Port Kembla for shipping to overseas customers.
Tailings Disposal
Three sets of slurry pumps, in parallel, pump the thickened underflow tailings to either of the two tailings dams or E27 (in-pit tailings). Water is retrieved from a decant system and returned to the plant.
