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At a Glance
- MIM (MIM acquired the remaining 49% on 27 June 2002)
- Reserves of 89 million tonnes at an average of 1% copper (as at 30 June, 2002)
- Significant gold credits at 0.53 g/t
- Average production of 100,000 tonnes a year copper and 125,000 ounces gold
- Commenced operations in August 1997
- Transition from contractor to owner operator for mining operations during 1999/2000
- It plans to improve metallurgical performance and costs in the face of reduced headgrades in 2002/03
- Awarded the inaugural Australasian Institute of Mining and Metallurgy Occupational Health and Safety Award for the development of an exceptional safety and health management culture
- Ernest Henry's current mine plan extends to 2012, exploration drilling is being undertaken to extend mining
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Overview
The Ernest Henry copper-gold mine, located around 38 kilometres north-east of Cloncurry in north-west Queensland, was officially opened in October 1997. Commercial production commenced in May 1998.
The mine plant provides for up to 10 million tonnes of ore to be extracted each year from an open cut operation to produce approximately 360,000 tonnes of concentrate containing 100,000 tonnes of copper and 125,000 ounces of gold.
The concentrate is transported by road to Mount Isa, about 117 km west of Cloncurry, for smelting by Mount Isa Mines, which has agreed terms to purchase all of Ernest Henry's concentrate.
Some 3,500 people were involved in building the mine at a cost of $310 million, more than 10% under budget.
The Ernest Henry project has been a major catalyst for significant infrastructure development in north-west Queensland benefiting the project and other users in the region.
Infrastructure developments included a 115 kilometre water pipeline, electricity transmission lines, upgrading and conversion of Mount Isa's Mica Creek Power Station from coal to gas, a new airport terminal and improved air services for a remote region.
Ernest Henry took over the operation of mining activities from a contractor in December 1999, resulting in lower mining costs.
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History
The mine is named after the explorer/prospector/miner Ernest Henry, born in England in 1837, who founded Cloncurry.
He explored the district in 1866, in the company of Roger Sheaffe. Sheaffe went on to establish Fort Constantine, the first pastoral property in the district.
Ernest Henry subsequently discovered numerous copper deposits in the district including the Great Australia and Mount Oxide.
The Ernest Henry mine is located within the present day boundaries of the Fort Constantine pastoral property.
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Geology
The Ernest Henry copper-gold deposit lies within a south-east plunging breccia system developed in a sequence of altered, porphyritic, intermediate volcanic rocks.
The breccia body dips 30 to 50 degrees south south-east and lies between a hanging wall sequence of variably altered felsic volcanic rocks and a footwall sequence of carbonate altered mafic volcanic rocks and siltstone.
Economic mineralisation is hosted by a breccia comprising strongly altered and replaced felsic volcanic fragments in a matrix assemblage of predominantly magnetite, chalcopyrite and carbonate.
The magnetite, copper and gold minerals are thought to have been introduced to these rocks around 1500 million years ago as a result of the nearby intrusion of a large granite pluton. Fluids from the granite passed through fractures, altering and replacing some minerals and forming the minerals present in the ore body - magnetite, chalcopyrite, pyrite, gold, cobalt molybdenum, rare earth elements and low levels of uranium.
Mineralisation boundaries are commonly sharp and conform to the limits of brecciation and fracturing.
The combined thickness of the mineralised sequence is around 250 metres, the width averages 300 metres. The ore body is open at depth and to the south west.
The upper portion of the mineralisation is weathered and variably oxidised and is classified as supergene ore.
This zone extends, in places, to 150 metres below surface and comprises about 12% of the entire resource. Supergene mineralogy is complex with copper occurring as native copper, bornite and chalcopyrite. Due to localised enrichment some of the highest copper and gold grades are present in this zone.
In the primary ore, copper occurs as chalcopyrite and gold occurs mainly in the molecular framework of the chalcopyrite. Copper to gold ratios stay consistent throughout at around 1% copper to 0.5 grams/tonne gold.
Mining processes
The Ernest Henry deposit, being close to the surface, is amenable to low cost, large scale open pit mining methods.
Over the 15 years of the currently planned mine life, in excess of 700 million tonnes of ore and waste will be mined. The pit will be mined in eight stages. Each stage will see the perimeter of the pit expanded and the overall depth of the pit increased. On current designs, the final pit will have a perimeter of 5 km, a diameter of 1.3 km and a total depth of 570 metres.
The scale of the mining allows large equipment to be used. The rock is drilled using rotary production drilling rigs. The rigs drill 17 metre deep holes of 270 mm or 311 mm diameter. Individual firings blast up to 500,000 tonnes of rock at a time.
The broken rock is loaded into 220 tonne capacity dump trucks by either a diesel-hydraulic shovel with a bucket capacity of 30m3 or an electric rope shovel with a bucket capacity of 43m3.
The 220 tonne dump trucks drive up a ramp at a gradient of 10% to deliver the ore to the crusher or waste rock to the dumps.
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Production processes
The Ernest Henry mine produces a value added concentrate on-site.
The concentrator is a single line plant using contemporary equipment, designed to treat nine million tonnes of primary ore a year, which equates to treating nominally 1,200 tonnes per hour.
Tailings are pumped to an engineered tailings storage facility for long term containment.
The concentrate is transported by road to Mount Isa where it is smelted and refined at MIM's copper refinery in Townsville, adding further value to the product within Queensland.
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Environment
MIM Holdings is committed to conducting business responsibly and in a manner designed to protect employees, the community's health and the environment. MIM Holdings developed an Environmental Policy and Standards in 1997 for all sites to follow to ensure minimal impact of our operations on the surrounding environment.
The design, development and operation of our facilities is managed with a view to reducing the impact of our operations; ensuring efficient use of energy, water and other resources; minimising waste generation and disposal; and where waste must be disposed of, doing so responsibly.
A high standard of environmental protection across all sites is maintained through site-specific Environmental Management Systems (EMS).
A key requirement of the EMS is the ongoing development of comprehensive Compliance Registers for all sites, which is an internal audit of sites' compliance with our environmental commitments.
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Surface water
The surface water management strategy at Ernest Henry focuses upon segregation of 'clean' and 'dirty' water catchments. Clean water is diverted around the site into natural drainage lines, while water that is potentially contaminated passes through sediment traps and is diverted to evaporation areas. The area of disturbance is kept to a minimum at all times.
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Groundwater management
The Ernest Henry operation is developing a pit that intersects a sub-basin of the Great Artesian Basin around 35 metres below the surface.
The main water supply for the operation is via a pipeline built from Lake Julius which is located roughly 110 kilometres to the west of the mine.
The operation is designed not to use groundwater as a primary water source. Instead only water required to maintain dry mining conditions in the pit is extracted. Extracted groundwater is used as a dust suppression and also as process water in the concentrator.
During 1998/99, a new subregional groundwater model was developed, focussing on the area in the immediate vicinity of the mine, using a greatly increased data set.
The original model indicated that impacts would be restricted to a 12-15 kilometre radius from the mine. The boundaries of the model extended to around 40 kilometre from the mine (compared to 200 kilometre for the original model).
The new model predicts off lease impacts of a similar magnitude to the original regional model. The model will continue to be refined in order for better assessing the potential impacts of the dewatering on groundwater levels.
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Acid rock drainage
Acid rock drainage (ARD) or acid mine drainage occurs when sulphides in mine waste oxidise to produce sulphuric acid. The acid can be mobilised by rainwater to produce a low pH, high salinity, solution that can then dissolve heavy metals.
The acidic metal laden leachate that results can lead to the contamination of both the surface and ground water. To combat the potential problem of ARD, Ernest Henry introduced a comprehensive program of waste identification, mine scheduling and waste rock dump construction and design to prevent the detrimental effects of ARD.
Computer modelling work helps with the ongoing design and management of Ernest Henry's waste rock dump to ensure that the potential for contamination by acidic water is minimised.
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Community relations
Ernest Henry has a "local content" policy where local businesses and people are favoured for supply of goods and services, all other things being equal.
The mine currently employs around 400 people. Almost half of the mine's employees are based in Cloncurry/north-west Queensland. The remaining are based in Townsville/north-east Queensland (30%) and Brisbane/south Queensland (21%).
Cloncurry is a rural township of around 3 500 people. Cloncurry has modern amenities and is host to significant regional events, including the Rotary Rodeo Merry Muster, the Cloncurry Show and the Ernest Henry Art Show, for all of which Ernest Henry Mining are major sponsors. Cloncurry is also a major cattle selling centre, providing in excess of 200,000 head of cattle annually for the live export market.
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Community reporting
Ernest Henry mine issues an annual community report. A down load is available of its most recent report covering the 2001 calendar year.
The report presents details of the Ernest Henry operation, the company's commitment to environmental management, key aspects of its environmental management program and details of direct and indirect benefits to the community.
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Local opportunities and training for aboriginal people
At the time when the Ernest Henry copper-gold mine was being developed, several existing Aboriginal groups in the north-west Queensland region formed a "peak body" to seek commercial and employment opportunities for Aboriginal people in the rapid economic development that was occurring in that part of Australia.
The body was named Koutha Aboriginal Development Corporation and received initial funding, encouragement and advice not only from Ernest Henry Mining but also from other businesses and the Queensland Government. (Koutha means "the water that provides life.")
As it had done at McArthur River a few years earlier, MIM and its joint venture partner made it known to the local aboriginal people that it was interested in involving them on a business basis at the Ernest Henry operation.
A joint venture was formed, Queensland Bulk Haulage Pty Ltd (QBH), to tender for the contract to truck the Ernest Henry mine's concentrate 160 km to Mount Isa.
The tender was successful, and the road haulage began in 1997. Around 1,000 tonnes a day is trucked to Mount Isa where it is smelted in MIM's copper smelter. The copper is then refined at MIM's Townsville copper refinery.
The QBH joint venture comprises the Koutha Aboriginal Development Corporation acting as trustee for the Pitmaikal Discretionary Trust and the Torres Strait Inland Commercial Development Corporation (CDC) with 25% each and McIver Transport Pty Ltd with 50%.
As well as joint venturing in QBH, Koutha is an accredited training organisation and places Aboriginal people in employment and training positions with mining companies and other enterprises in the region, including the Ernest Henry mine.
During 1998/99, the Ernest Henry mine signed a Memorandum of Understanding with Koutha on employment and training commitments, formalising the understanding that has been developed between the two organisations. From July 1999, EHM became host employer to several Koutha trainees and apprentices.
A second group was hosted from October 2000 in what will be an ongoing programme.
MIM's Indigenous employment and community initiatives are outlined in a case study featured in the Commonwealth Department of Industry, Resources and Tourism's Working in Partnership Programme.
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