Gruyere Gold Project, Melbourne, Australia
Located in the Yamarna Greenstone Belt, Gruyere Gold Deposit is situated on mining lease M38/1267, approximately 200km east of Laverton in Western Australia.
With estimated ore reserves of more than 3.5 million ounces (Moz) of gold, to be produced over an initial 13-year mine life, the project is claimed as one of the most significant undeveloped gold deposits in Australia.
The project was previously wholly owned by Gold Road, which recently announced a 50:50 joint venture (JV) with an Australian subsidiary of Gold Fields for the development and operation of the project.
Pursuant to the transaction, which is expected to close before December 2016, Gold Fields will acquire a 50% interest in the Gruyere Gold project for a cash consideration of A$350m ($268.426m), including A$250m ($191.73m) payable upon completion of the transaction and the remaining during the construction phase.
The prefeasibility study (PFS) of the project was completed in February 2016, followed by the commencement of the feasibility study (FS), which was completed in October 2016.
The project is estimated to cost A$507m ($370m) and produce 270,000oz of gold a year.
Geology and mineralisation
The Gruyere Deposit comprises a porphyry intrusive dyke, which strikes over a length of 2,200m. A combination of intermediate to mafic volcaniclastic rocks and a tholeiitic basalt unit occur at the east and west sides of the deposit.
Mineralisation at the deposit is associated with albite-sericite-chlorite-pyrite alteration, which changed the primary texture of the rock composed of fine quartz-carbonate veins. The primary sulphide mineral is pyrite with some visible gold found in logged diamond drill core.
Gruyere gold project reserves
As of November 2016, the Gruyere project is estimated to hold combined probable and proven reserves of 91.6Mt grading 1.20g/t and containing 3.52oz of gold.
Mining and processing at the Gruyere gold mine
Open-pit mining will be applied to mine the deposit using conventional mining equipment. Loading and hauling will be done using 360t excavators and 180t haul trucks respectively. The loading fleet will comprise three 360t hydraulic excavators, while the ore and waste haulage fleet will consist of 180t mechanical drive haul trucks.
Processing at the mine is proposed to be in a single-stage primary crush, semi-autogenous grinding and ball milling with pebble crushing (SABC) circuit. It also includes a conventional gravity and carbon-in-leach (CIL) process.
The facility will have a design capacity to process 7.5Mtpa of fresh ore, 8.0Mtpa of transitional ore and up to 8.8Mtpa of oxide ore.
The project site can be accessed from Laverton along the Great Central Road. A gas-fired power station was proposed as a preferred power generation solution for the project. With a design capacity of 40MW, the power station will be capable of producing peak load requirement of the plant.
Water for the plant operation will be sourced from the Yeo Borefield located approximately 25km west of the project site. The borefield will supply 7.5GL of moderate to high-saline water a year to be used as process water.
Also planned is an accommodation village with 300 permanent and 300 temporary accommodation rooms to be constructed roughly 6km from the project site. It will also have support service buildings, including administration and mess facilities.
Adjacent to the village, an airstrip with a 2.1km-long runway, terminal and fuel facility will be constructed. It will be able to handle 100-seat aircraft.
A tailings storage facility (TSF) with a surrounding waste dump will also be constructed. The waste generated will be dumped into the TSF using traditional dump construction techniques.
The technical report for the Gruyere gold project is being compiled by Behre Dolbear Australia (BDA). A number of the key consultants involved in the feasibility study are GR Engineering Services (GRES), AMC Consultants, Pennington Scott, Dempers and Seymour, and MBS Environmental (MBS).