Papua New Guinea
Newcrest Mining Ltd. - 100%
|Operator||Newcrest Mining Ltd|
Gold - 700k oz per annum
|Deposit Type||Epithermal gold deposit|
|Reserves & Resources||
Gold - 31 Moz (June 30, 2011)
|Mining Method||Open pit|
|Processing Method||Flotation, pressure oxidation|
|Mine Life||To 2023|
|Mining Equipment||Truck & shovel|
Crushers, grinders, flotation circuit, autoclaves
PO Box 380
Phone:(+675) 986 4014
Last updated: Jun 8, 2012
Lihir Gold's operation is located on Niolam Island, 900 kilometres north of Port Moresby in the New Ireland Province of Papua New Guinea. As Niolam Island is the principal island of the Lihir Group, it is generally referred to as Lihir Island.
Lihir is a volcanic sea mount that rises steeply from sea level to approximately 600 metres above sea level. At its widest points, the island measures 22 kilometres from north to south and 14.5 kilometres from east to west.
The Luise Caldera, in which all of the known ore deposits are located, is on the east coast of the island. Exploration work has identified several adjacent and partly overlapping mineral deposits in the Luise Caldera, the principal ones being Lienetz, Minifie, Coastal and Kapit.
The ore body was discovered in 1982 and exploration was conducted between 1983 and 1995 when construction of the mine and process plant commenced. Production began in May 1997, and since that time the mine has produced more than seven million ounces of gold. In 2008 the operation's gold production was 771,000 ounces, extracted using open pit methods and a pressure oxidation and carbon-in-leach (CIL) process.
The mine consists of a single ore body with three linked open pits that will be mined over the project life. The operation is currently focused on the processing of approximately 6 million tonnes of ore, with around 4 to 6 million tonnes of lower grade ore stockpiled annually. The mine currently (2011) has 31 million ounces in reserves and 56 million ounces in measured and indicated resources.
Lihir Island is a volcanic sea mount that rises steeply from sea level to approximately 600 metres above sea level. Flat land comprises only 15% of the landmass. At its widest points, the island measures 22 kilometres from north to south and 14.5 kilometres from east to west.
The island is made up of five volcanic units, of which three are recognizable volcanic craters (containing the Luise Caldera). The Luise Caldera is the youngest volcano at less than one million years. It is open to the sea on its northeast side, forming the Luise Harbour. Remnant volcanic activity is evidenced by fumaroles and hot springs.
Lihir Island is situated within an area of intensive earthquake activity (the Pacific Rim of Fire), and is surrounded by narrow, fringing coral reef, less than 100m wide, beyond which steep submarine slopes descend to a depth of 2,000m, between five and fifteen km offshore.
The climate is tropical, with temperatures varying between 20Â°C and 30Â°C (68Â°F and 86Â°F). The island averages 12 feet (3.7 meters) of rain a year.
Most of the island is covered by dense blanket of rainforests and an exotic tangle of vines, creepers, flowers, plants and trees. Orchids blaze from the green ground of rainforest canopy.
Lihir island is made up of 5 Miocene-Pleistocene volcanic units, of which 3 are recognizable volcanic craters (containing the Luise Caldera) and 2 are sequences of mafic volcanics that predate the three volcanoes.
In a nutshell Lihir is an epithermal sulphide ore deposit hosted by an inactive volcanic crater.
Remnant geothermal activity is present in the Luise caldera, which has hot springs and fumeroles. The orebody is contained in a hydrothermally-altered porphyry gold system with the gold hosted in volcanics, intrusives and breccias within the caldera. The majority of the gold is contained in sulphides. Gold occurs primarily as sub-micron sized particles within sulfide minerals. The main sulfide mineral is pyrite, with the average sulfide content of the reserves at 6.15% S.
Currently defined gold mineralisation occurs near the centre of the caldera. Exploration since 1983 has defined several adjacent and partly overlapping deposits; Lienetz, Minifie, Coastal and Kapit with adjacent satellite deposits of Borefields and Camp. The bulk of the known mineralisation is in Minifie and Lienetz. All of the deposits except Minifie are connected by areas of low-grade mineralisation.
Approximately 50 million tonnes of material is moved from the pit each year. Of this total, approximately 10 million tonnes is ore, of which around 4 million tonnes is stockpiled for future processing. The remaining 40 million tonnes is waste. Mining of the deposit is planned to continue until around 2023, after which time ore will be reclaimed from the stockpiles and processed for at least a further decade.
The remaining life-of-mine strip ratio is about 4:1 (waste: high-grade ore + low-grade ore).
The planned final dimension of the pit is approximately 2 kilometres x 1.4 kilometres, with a final depth of 200 metres below sea level. Bench heights: 12 metres and 6 metres. Maximum final pit slope angle: 47Â°.
Ore from the Lihir mine is refractory, which means it requires pressure oxidation using autoclaves to release the gold. The plant's facilities first crush and grind the ore, and a flotation plant is used to concentrate a portion of the material as required, before it is fed to the autoclaves for pressure oxidation followed by conventional CIL technology. The process plant is currently capable of treating over six million tonnes of ore per annum with the capacity to produce in excess of 800,000 ounces of gold per year at the current gold grade.
In 2008 a major expansion to the Lihir process plant to increase annual gold processing capacity to approximately one million ounces per year was approved. The project is focused on the installation of an additional autoclave to the process plant that is of a wider diameter and double the capacity of each of the three existing autoclaves. Annual throughput will increase to a maximum of around 11 to 12 million tonnes, lifting gold production by up to 240,000 ounces per year.
Lihir mining operations use the site's geothermal steam to generate electricity. Total geothermal capacity is of 56 MW.
The company works closely with the Papua New Guinea government to implement its environmental monitoring and management plan. This now incorporates a mine closure plan and acid rock drainage prevention systems. In 2004 Lihir was the first mine in Papua New Guinea to achieve ISO 14001 accreditation for its environmental management system.
An environmental laboratory has been built and field and laboratory equipment provided for air and water sampling, steam gauging, sediment sampling, fish sampling, weather monitoring, oceanographic monitoring and industrial hygiene measurements.
Before the mine opened the island was relatively isolated from the rest of Papua New Guinea. Infrastructure and public services to Lihir and the neighboring islands were limited. The only source of education was provided by missionaries. Only a few roads were constructed around the island and a small airstrip connected Lihir to the mainland. Now the island has a major airport and a ring road connecting villages on the island. There is a town with school and health care services. The company has built village infrastructure including housing, water and power supplies, and meeting halls and churches.