|Private Mail Bag 6|
Mount Isa, Queensland
Tel: 61 7 4744 2011|
Fax: 61 7 4744 3731
Time: AEST (Brisbane)
Contacts: none available
Mount Isa Mines Limited (Xstrata Plc) operates two separate mining and processing streams, copper and zinc-lead-silver, at Mount Isa. Together the company's 4 underground mines form one of the largest underground mining operations in the world.
Xstrata's Mount Isa copper operations consist of 2 underground mines, X41 and Enterprise and a concentrator with a 7.2 Mt/y copper capacity and smelter with a 300,000 t/y copper anode capacity. The zinc-lead-silver operations consist of the George Fisher (formerly Hilton North), Black Star and Handlebar Hill open pit mines, a zinc concentrator with a 6.5 Mt/y capacity, a lead smelter and a zinc filter plant. Together these mines produce over 226,000 t/y zinc concentrate and 125,000 t/y lead and 8.26 Moz/y silver in lead bullion.
Discovered in 1923 with
production commencing in 1931, Mount Isa is Australia's and one of the world's largest underground mining complexes. Even though the existence of copper ore in quantity was confirmed in the 1930's, it was not mined until a wartime scarcity of copper brought a request from the Australian Government. In 1943, the mine ceased silver-lead-zinc production and switched to copper to help the war effort. In 1946, copper mining stopped, and the mine reverted to silver-lead-zinc. Parallel production of silver-lead-zinc and copper ores commenced in 1953 and continues to this day.
With the recent development of the Black Star open cut, Mount Isa has reserves to support a mine life of approximately 11 years. The George Fisher/Hilton mine has reserves to support a mine life of approximately 15 years.
Xstrata employs more than 3200 employees and 1100 contractors at Mount Isa.
Mount Isa, Queensland, Australia, is a thriving outback city approximately 1000 km west of Townsville, 2000 km northwest of Brisbane, and 1600 km east of Darwin and Alice Springs. Mount Isa Mines is based here and has massive mining and mining support operations along with other major mining companies operating in the region.
Mount Isa is vast. It covers 41,000 square kilometers and is located among the ochre-red Selwyn Ranges on the banks of the Leichhardt River. The Lawn Hill Gorge in Boodjamulla National Park and the world-heritage listed Riversleigh Fossil Fields are nearby. Deep in dinosaur fossil country, the rocky terrain is harsh but beautiful, a rugged 'Mars-like' landscape with stark striking colours.
The population is 23,500 and is a significant administrative centre for the region. Although situated in an arid area, the artificial Lake Moondarra to the north provides both drinking water and an area for watersports. The city hosts Australia's largest rodeo annually and is in the center of some of Australia's biggest cattle stations.
Mt. Isa is well-connected with the rest of the country. There is overnight passenger train to Townsville twice a week; the Mount Isa Airport has regular daily services to Brisbane, Townsville and Cairns, and many remote outback communities in western Queensland; Mount Isa is on the Barkly Highway, which connects Townsville with the Northern Territory.
Queensland enjoys warm weather and a sizable portion of the state is in the tropics. Mt. Isa is usually hot and sunny. Summer temperatures (December and January) range from 24 to 37°C and winter temperatures (June and July) from 11 to 26°C.
It is believed that the copper orebodies were formed about 1,500 million years ago within the Urquhart Shale Formation, in a sequence of alternating pyrite-rich dolomitic siltstone and shale beds up to 1000 metres thick.
The zinc-lead-silver orebodies extend from the surface to about one kilometre below the surface. Individual orebodies range in widths up to 35 metres and may persist for hundreds of metres in length.
The large 1100 copper orebody extends from 400 metres to 1000 metres below the surface. It is three kilometres long and one of the largest and richest copper orebodies in the world.
The main copper mineral is chalcopyrite. Closer to the surface, weathering and ground water leaching has changed the chalcopyrite to secondary copper minerals such as chalcocite. This weathering has also affected some of the near-surface lead orebodies, forming cerussite, a secondary lead carbonate mineral.
The George Fisher orebodies are very similar to the Mount Isa zinc-lead-silver orebodies. They are narrower and disrupted by more folding and faulting. There is less copper as well.
A significant increase in known copper resources has led to a planned 40% expansion in copper production by 2006. Resources sufficient to support a 400,000 tpa rate for up to 20 years from Mount Isa and Ernest Henry was announced in 2002.
Mount Isa operations are carried out in two production streams. Copper operations consist of the X41 (1100 and 1900 orebodies) and Enterprise (3000 and 3500 orebodies) underground mines along with a copper concentrater and smelter. Zinc, lead and silver operations consist of the Hilton and George Fisher (formerly Hilton North) underground mines and the Black Star open pit mine.
Underground operations are accessed via surface shafts, two equipped with ore hoists, and a decline, which is shared with the Isa Lead mine. Both the interconnected X-41 and Enterprise mines contain massive orebodies, which are extracted using long-hole open stoping with delayed backfill. Operations are mechanised with a complement of rubber-tired trucks and loaders, electro-hydraulic drilling rigs, raise boring rigs and ancillary vehicles.
The main ore hoisting shaft for the Mount Isa copper operations is the 710-m deep U-62 shaft from surface. The R-62 shaft, located near U-62 is an ore hoisting and service shaft for personnel and supplies to the copper mine. R-62 is also the main ore hoisting facility for the Isa Lead mine, and is also used to feed copper ore to the lead concentrator when required. The internal M-62 shaft is used for hoisting ore from the deep Enterprise zone to the crushing and conveying system at the base of the U-62 shaft. A decline from surface, also shared with the Isa Lead mine, can be used for movement of personnel, materials and equipment into the Enterprise area.
A variety of mining methods have been used at Isa during the course of its operation. Sub-level open stoping (''SLOS'') is the method currently used in both the X-41 and Enterprise areas of the mine. SLOS is designed to extract massive blocks of ore in vertical slices throughout the orebodies. Stope sizes in the large 1100 ore body (X-41 area) are mined in blocks of 40 metres by 40 metres, and up to 300 metres high. Drilling sublevels for the blocks are developed at every 40 metres of elevation. Stope sizes in the 3000 orebody (Enterprise area) are as small as 25 metres by 25 metres, and up to 100 metres high. Drilling sublevels for mining the 3000 orebody are spaced approximately 25 metres apart. Blast-hole drilling is carried out using mechanised drill rigs. The broken ore is collected at the bottom of the stope and is extracted at drawpoints by load-haul-dump (''LHD'') mining equipment.
Enterprise zone stopes are extremely hot with virgin rock temperatures reaching 60 degrees centigrade (''C'') at the bottom of the mine. Mount Isa cools the mine with some of the largest refrigeration plants in the world, which are located on the surface near the R-62 shaft. Enterprise ore is trucked or hoisted to the U-62 crusher and hoisted to surface. Ore from X-41 is transferred to a crusher and onto an underground conveyor system for subsequent hoisting through the U-62 shaft from the mine.
Completed stopes in the X-41 area are backfilled using a combination of waste rock mixed with a cement slurry, while Enterprise stopes are filled with mill tailings mixed with cement, much of which is introduced as paste fill. The current deepest part of the Enterprise mine is 1,600 metres. High rock stresses coupled with talcy, blocky ore in the Enterprise orebodies cause delays in mining. Prompt backfilling of completed northern Enterprise stopes is necessary to prevent major ground movements resulting from the high rock stress conditions.
At Mount Isa's Blackstar open pit mine, the copper-gold ore is crushed in a gyratory crusher, ground in a SAG-ball mill, and processed in a flotation plant for the production of a copper-gold concentrate. The copper-gold concentrate is predominately trucked to Mount Isa for smelting with the excess shipped to Townsville for transport to third-party smelters.
In September 2007, operations commenced at the Handlebar Hill open cut zinc-lead mine and will provide an additional 4.3 million tonnes of ore to Mount Isa's zinc-lead reserves.
In 1999, a major expansion of the Mount Isa copper smelter was undertaken to increase smelter capacity and improve operating costs. The project was completed in 1999. Smelter capacity increased to more than 250,000 tonnes of copper anode per year to accommodate all mine production from Ernest Henry mine as well as Mount Isa.
The Hilton concentrator recovers three products shipped to Mount Isa as slurry. It uses SAG milling, tower-mill regrinding and flotation with company-designed column cells and Jameson cells. The plant reached rated output shortly after commissioning but switched to treating copper converter slag from Mount Isa in the mid 1990s when the mining rate was cut and ore was trucked to the Mount Isa lead-zinc concentrator.
Long-run processing of 2.5Mt/y ore from George Fisher required modifications and general upgrading at the Mount Isa lead-zinc concentrator and lead smelter. Engineering contractors Bateman Brown & Root reconfigured the flotation circuit was to incorporate IsaMill technology for very fine grinding and froth pumping. This yielded a near 10% performance improvement in recoveries to 78.8% Pb and 73.4% Zn, with the zinc recovery rising to 80.7% in FY2002. In the lead plant the sintering machine was rebuilt, the blast furnace crucible replaced and a new control system installed.
By the end of 2008, an expansion to the Mount Isa zinc-lead concentrator is scheduled for completion, increasing capacity to 8 million tonnes per year. Zinc production will increase to 340,000 tonnes, doubling output since Xstrata acquired Mount Isa in 2003.
The Mount Isa copper smelter produces copper anode from ore mined in the two Mount Isa underground copper mines and from the Ernest Henry open-cut mine. The company has begun an A$7.2 million leaching project to recover around 2500 tonnes per annum (tpa) of additional copper from electrostatic precipitator dust in the Mount Isa copper smelter.
A project to expand the capacity of the Mount Isa copper smelter has also begun at an expected capital cost of A$41 million. The project comprises the installation of a second rotary-folding furnace, a copper slag-cleaning furnace, a converter slag-cleaning plant and associated plant, all designed to increase the smelter's capacity from 240,000 to 280,000 tpa by mid-2006.
The project will also improve the copper smelter matte process recoveries between the copper ISASMELT furnace and the copper converters by 2%, reduce unit operating costs, and improve the overall operating control of the copper smelter.
Copper anode from the Mount Isa smelter is sent by rail to be refined at Xstrata's Townsville copper refinery to produce 99.995% pure London Metal Exchange (LME) grade A copper cathode.
Environment and Community
There are a number of environmental projects currently underway at Mount Isa. These include progressive rehabilitation of tailings dams, a focus on site clean-up including the demolition and removal of obsolete site infrastructure and a review of water management on the lease including
improving stormwater run-off.
Mount Isa Mines has taken major steps forward in capturing waste sulphur dioxide. Since 2000, sulphur dioxide emissions from the copper smelter have been reduced by 77% and 33% from the lead smelter. The target is to, by 2012, to reach or exceed 95% capture and treatment rate of sulphur dioxide emissions from the copper smelter and a 98% capture and treatment rate from the lead smelter.
Since Xstrata's involvement with Mount Isa Mines in mid-2003, Xstrata has spent over $200 million on more than 80 environmental improvements. Some of these include reduction in emissions from smelters, independent studies to identify pathways of lead into the community, continuing safety procedures on-site to minimize employees' exposure to lead and reduce the risk of lead being taken into the community. The company is also removing historical mine sediments from the Leichhardt River. The green buffer zone between the mine and the community is a continuing project with an annual budget of $500,000 for rehabilitation. The buffer zone was originally established in 1991 at a cost of $8 million after a remediation program was conducted in conjunction with the local Council and the EPA to address areas of historic contamination caused by previous mining practices.
From a community standpoint, all Mount Isa Mines employees reside in Mount Isa. The wages paid by the company as well as payments to local contractors and suppliers make the company the major contributor to the citys economy. Xstrata is proud of its role in creating jobs and supporting local communities through programs, such as Xstrata's Community Partnership Program. These programs are delivering over $22 million in support for community programs throughout Queensland - $11 million in north Queensland and $11 million on State-wide initiatives. The company is a major sponsor of the annual Rotary Rodeo and has been a long-term supporter of many other local charities and appeals.