The Nullagine gold mine is an open-pit mine located in the East Pilbara District of Western Australia. Millennium Minerals fully owns the project and expects to produce 73,000 ounces of gold per annum from the mine.
The project is a combination of seven deposits taken on lease. Golden Eagle, the largest deposit of the gold project, comprises more than 60% of the total mineral resource.
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The mining activities at Nullagine began in July 2011 and gold production commenced in September 2012. The mine produced 16,441oz of gold for the June 2013 quarter at a recovery rate of 89%. It is currently expected to have a mine life of seven years.
Nullagine mine also holds mineral resources in sulphide ore, which was not developed due to lack of a suitable processing route. Millennium Minerals initiated a two stage expansion of the existing carbon-in-leach (CIL) plant to process the sulphide ore. First gold production from first phase of stage one expansion started in June 2019. Stage two of the expansion is expected to be completed in 2020.
Nullagine gold mine geology
The Nullagine gold mine is a part of the Mosquito Creek Belt and is characterised by turbidite-hosted rock deposits of the De Grey group. The belt is structurally controlled by faults and quartz vein arrays.
The Golden Eagle deposit is made up of deformed meta-turbiditic rocks and lies on the upright limb of a reclined plunging. Mineralisation occurs as a fractured wall rock surrounded by gently inclined faults.
Greenschist facies metasedimentary rocks host the satellite deposits at Nullagine. The mineralisation at these deposits is located within or near the sharply inclined quartz veins.
Nullagine gold mine reserves
The Nullagine gold mine has reserves of 1.16Moz of high-grade gold. The combined measured and indicated resources have been estimated at 7.49Moz as of December 2018.
Gold mining and ore processing at Nullagine
Gold is mined through underground mining methods from six mining centres at Nullagine. The ore at the Golden Eagle deposit is conveyed to the 150,000t capacity run-of-mine (ROM) stockpile area and is fed into the ROM crusher feed bin for crushing.
The crushed material is transferred by conveyor belts to a 50,000t live capacity coarse ore stockpile. The grinding circuit includes a single stage 4,000kW Semi Autogenous Grinding (SAG) mill in closed circuit with hydrocyclones.
The processing plant at Nullagine is a 1.5 million tonne a year CIL plant. The processed ore is treated in the gravity and CIL circuits. The tailings storage facility is located approximately 1km north-west of the plant site.
A second underground mine is planned to be developed at the Golden Eagle deposit in 2019.
Sulphide plant expansion
The expansion of the CIL plant commenced in April 2019. The first phase of stage one expansion included the installation of a concentrator and fine grinding circuit, while the second phase included installation of the in-mill oxidation process.
The second stage of expansion will involve pressurised in-mill oxidation (PINOX).
Infrastructure facilities at Nullagine mine
The plant site includes a diesel generator power house equipped with nine 1MW diesel generators.
The water supply for the milling circuit was provided from the production bores along with the water from the tailings dam. Lined water dams were constructed adjacent to the plant in order to store the process water and the raw water.
Financing for the Nullagine gold mine
The Nullagine gold mine received financial support of $35m from BNP Paribas and National Australia Bank. The financing also includes $10m lease finance from National Australia Bank.
Millennium Minerals also raised $23.2m through a rights issue. The amount was used for the leasing of transportable buildings, mobile equipment and other elements required for the project development.
Contractors involved with Nullagine gold mine development
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The engineering, procurement and construction management contract for the Nullagine gold project was awarded to Mintrex.
Kalgoorlie Power Systems (KPS) was awarded the contract to build, own and maintain the 9MW power station at Nullagine gold mine.
Interquip was contracted for the structural, mechanical, and piping works at the Nullagine processing plant.
Western Plant Hire is supplying and maintaining the mining load/haul fleets along with a crusher feed and ancillary equipment.
Coffey Geosciences conducted the study for the tailings storage facility strategy and surface water management issues.
Resource Services Group and Hellman & Schofield conducted the resource estimation and scoping studies at Nullagine.
