The Abra base metals project is a high-value, high-grade lead-silver concentrate project being developed in Western Australia. Set to be one of the world’s biggest primary lead mine upon reaching full production, the project also has copper-gold mineralisation at depth.
The pre-feasibility study for the base metals project was completed in September 2018. Galena Mining, the project developer, proposes to commence a feasibility study in late-2018 and complete the same in mid-2019.
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The project is expected to produce high-grade lead-silver concentrate containing 91,000 tonnes per annum (tpa) of lead and 760,000oz per annum of silver over its anticipated mine life of 14 years.
Location and geology of Abra base metals project
The Abra project is located approximately 200km north of Meekatharra in the Gascoyne region of the central part of Western Australia, while the tenements can be accessed by public unsealed roads through the Great Northern Highway.
The deposit is located within the sediments of the Proterozoic Edmund Group, and hosts lead as primary economic metal. It also contains silver, copper, zinc and gold in lesser quantities.
Sediment-hosted replacement style of mineralisation is found at Abra, with the upper sections featuring stratiform lead-silver horizons that dip shallowly to the south.
The project is divided into two main parts, namely the upper Apron zone and the Core zone. The Apron zone comprises stratabound massive and disseminated lead sulphides (galena) and minor copper sulphides (chalcopyrite). It extends for 1,000m along strike and gently dips 700m downwards to the south.
Located beneath the Apron zone, the Core zone comprises hydrothermal breccias, veining and intensely altered overprinting sediments. The veining and breccia zones in the Core typically dip steeply to the north.
Mineralisation
Most of the high-grade lead sulphide mineralisation is contained in the intensely veined zones of the Core zone, while high-grade zinc sulphide mineralisation (sphalerite) is found in the central parts. Copper (chalcopyrite) and gold mineralisation is occasional throughout the upper parts of the Core zone but is found consistently at the base.
Abra base metals mine reserves
The Abra base metals project is expected to contain reserves of 10.5Mt, grading 8.1% lead and 20g/t silver.
Mining and processing at Abra
Conventional underground mining method, using long-hole open stoping, will be applied as the primary mining method, with paste backfill. Shallow dipping areas within the Apron Zone will be mined using the room and pillar method.
The processing plant will employ single-stage primary crushing and semi-autogenous grind milling comminution to produce high-value, high-grade lead-silver concentrate.
It will comprise a lead flotation circuit featuring roughing and scavenging followed by regrinding of rougher scavenger concentrate. The concentrate will undergo two stages of cleaning to contain an average grade of 75% lead and 220g/t silver at a recovery rate of 96% for both the metals.
The lead-silver concentrate will be thickened, filtered, loaded in containers and transported on the Ashburton Downs Meekatharra Road to the Port of Geraldton for shipping.
Financing
Galena Mining raised A$9m ($7m) by issuing approximately 58 million new shares, priced at A$0.15 ($0.12) a share, in a private placement in April 2018.
Part of the proceeds are intended for undertaking infill and expansion drilling at the lead-silver project, the completion of the PFS and to advance the bankable feasibility study of Abra.
Hartleys was the lead broker for the transaction.
Contractors involved
Galena engaged GR Engineering Services (GRES) for supporting the company in preparing the PFS. GRES has conducted detailed process design, metallurgy review, mass water and energy balances, plant layout and general arrangement drawings, capital cost and operating cost estimation, and infrastructure design, as part of the contract.
Mineralis Consultants (Mineralis) was engaged to manage a testwork programme and prepare a high-level process design and block flow diagram/flowsheet for the overall process.
Galena has also engaged consultants such as Rockwater, AMC Consultants, Mine Projects and Development Services, Jacobs Engineering Group, Stantec, Land & Marine Geological Services, CorpCloud, and WH Cunningham for the PFS preparation.
