The Odysseus nickel mine is an underground mine located within the high-grade Cosmos nickel operation in Western Australia which was acquired by Australian nickel producer Western Areas from Xstrata Nickel Australasia in 2015.
The construction of the twin declines for the new underground mine was underway of September 2020. The pre-capital investment for the project is estimated to be approximately £170m (A$299m) and the first nickel pour is expected by the second quarter of 2023.
Western Ares is also undertaking development works at the adjacent AM5 and AM6 deposits with a plan to incorporate them to the Odysseus production profile. The incorporation of these two deposits will extend the mine life beyond the currently estimated 10 years.
Project location and geology
The Odysseus nickel mine lies within the Cosmos nickel mine complex, which is located approximately 30km north of Leinster in the fertile Leinster‐Wiluna nickel camp in Western Australia.
The Odysseus deposit comprises two sulphide mineralisation zones namely North and South that mostly consist of pentlandite with minor pyrrhotite and pyrite.
The North deposit has a strike length of 380m with an average thickness of 51m at 1000-1075m below the surface, while the South deposit sits at the same depth with a strike length of 360m and an average thickness of 62m.
Mineral reserves at Odysseus
The mineral reserves at the Odysseus deposit were reported to be 8.13 million tonnes (Mt) grading 2% Ni and containing approximately 164.5kt of nickel as of June 2020.
The Odysseus underground mining operation will utilise the single‐lift long‐hole open stoping with paste fill method. A 50m cross-cut spacing will be used for the transverse ore drives for paste fill works. Out of the total ore reserve, approximately 89% will be recovered through long-hole stopes while the remaining 11% will be derived from the ore drive development.
A new single ramp decline from the existing AM5/6 decline development will be used to access the Odysseus deposits. The North and South deposits will be mined in a top-down, centre-out sequence, while the average stope size will be 15m-wide along a strike length of up to 29m. The spacing between the stopes will be 25m, and each stope is estimated to access up to 30,000t of ore. Backfilling will be done with paste fill produced from recycled tailings.
The primary ventilation shaft consists of a 5m-wide and 1000m-deep intake shaft which will also serve as a production hoisting shaft and a partially reamed 5m exhaust raise. The hoisting shaft will be capable of accommodating up to 1.1Mt of ore and waste a year and will be equipped with a mid‐shaft loading station (MSLS) and a bottom shaft loading station (BSLS).
Hauling of ore and waste will be carried out at the BSLS via 50t trucks through a grizzly containing two rock breakers. The coarse ore will be fed to a sizer via an apron feeder to reduce the feed size to a maximum of 150mm. The feed material will then be fed into two 12.5t skips and hoisted to the surface for transportation via a conveyor to the surface stockpile.
Ore processing will be done at the existing Cosmos processing plant which will be upgraded to increase mill throughput to 1Mtpa. The expansion will involve the installation of a secondary crusher, conveyors, and reconfiguration of the grinding mills along with additional flotation capacity.
The run-of-the-mine (ROM) ore will undergo two-stage crushing and grinding before being transferred to the flotation circuit to separate the nickel-containing sulphide from foreign particles.
The froth flotation concentrate will undergo regrinding to further purify the nickel-bearing concentrate, while the waste from the flotation circuit will be transferred to the tailings thickener and stored in the tailing’s storage dam. The nickel bearing concentrate from the thickening circuit will be filtered to produce the final nickel concentrate.
Infrastructure facilities for the Odysseus mine development
The Cosmos nickel complex is accessible by gravel road from the sealed Goldfields Highway. Fly-in-fly-out (FIFO) facilities are also available from the BHP Nickel West FIFO facilities.
The aerodrome at the Cosmos mine site will be upgraded to facilitate FIFO travel arrangements once staffing at the mining operation reaches the desired level.
Staff accommodation is also available at the Cosmos village which has a maximum accommodation capacity of 540.
The project is estimated to require 20MW of electricity supply which is expected to be met through diesel generators as well as renewable power resources. A 13km lateral gas spur line is proposed to be constructed next to the existing Cosmos lateral spur line which connects the Cosmos power plant to the Goldfields Gas Pipeline (GGP).
Water supply will be received from the Yakabindie bore field to the reverse osmosis plant which supplies the mining camp. The process water will be pumped from the underground mine.
Barminco was awarded the Odysseus mine development and production contract for a period of five years in September 2020. Earlier, Barminco was also engaged in the rehabilitation works at the mine site.
GR Engineering Services was awarded for the design and engineering works for the Cosmos processing plant expansion.
The mine planning and optimisation works were completed by Piran Mining while KCSA Geomechanics and Golders were responsible for geotechnical engineering works with SRK Consulting engaged in geological modeling works.
Outotec, a Finnish technology company, provided the paste fill engineering, plant design, and testing services.
RSV International was responsible for the shaft engineering and design, while Dempers & Seymour provided the mining rock mass modeling services.