Azure Minerals is developing the high-grade Oposura zinc-lead-silver project in Sonora State, Mexico. It is estimated to involve a pre-production CAPEX of approximately A$70m (£38m).
The project is expected to produce roughly 35,000 tonnes (t) of zinc concentrate and 16,000t of lead concentrate a year, through an estimated mine life of six years. The concentrates are expected to contain approximately 19,000t of zinc, 10,000t of lead, and 145,000 ounces (oz) of silver.
Pre-feasibility and definitive feasibility studies of the project are expected to be completed by mid-2019 and late-2019, respectively.
Azure is currently focusing on commencing small-scale trail mining and toll treatment in the September quarter of 2019. Construction on the project is anticipated to be completed by the end of 2020, with first production expected to be started in late-2020 or early-2021.
Oposura zinc-lead-silver project geology and location
Oposura project is located to the north-east of the Sonora state and approximately 200km south of the international border with the US.
The project site is situated within the western Mexican Sierra Madre Occidental Basin and Range tectonic zone. A distal skarn, stratabound, disseminated to massive zinc and lead sulphide deposit type is found at the Oposura mine site.
Mineralisation is primarily found within a Cretaceous-age felsic volcano-sedimentary sequence that comprises the Arenillas Formation. The footwall unit of the area is the Revancha Rhyolite and the hangingwall unit is the Candelaria Formation.
Oposura mine reserves
The Oposura zinc-lead-silver project is estimated to contain JORC-compliant mineral resources of 3.1 million tonnes (Mt), grading 5.0% of zinc, 2.7% of lead, and 18g/t of silver.
Mining at Oposura project
Shallow open-pits will be constructed to access the underground Oposura zinc-lead-silver project, followed by room and pillar extraction method. The mine is estimated to recover 500,000tpa (1,500tpd) of ore through its mine life.
High-grade mineralisation will be targeted during the first month of the open-pit mining in the East and West Zones, while underground mining will be focused on pits B and C in the West Zone.
Trial mining is proposed to be conducted at Tunnel D HG zone, an approximately 250m-long zone containing high-grade, zinc-rich mineralisation.
The open-pit mining fleet will include Komatsu PC1250 excavator, Komatsu HM400 trucks, Sandvik Leopard DI450 production drill, CAT 914M front end loader, CAT D9 dozer, and CAT 12M grader.
The equipment for the underground mining will be Atlas Boomer S2 Twin boom Jumbo drill, Boomer S1L, CAT 1300, CAT 170 loaders, and Komatsu HM400, Atlas MT436B trucks.
Run-of-mine ore from the Oposura project will be subject to two stages of crushing in closed circuit with a double-deck screen. The undersize from the primary crusher will be fed into the ball mill, while the oversize will be recycled to the secondary crusher and sent to dense media separation (DMS).
The DMS plant will remove the lighter density gangue material, while the resultant product will be forwarded to grinding and flotation circuits. Lead sulphides will be passed through a rougher and two-stage cleaner flotation cells to produce lead concentrate, while silver will be recovered to the lead sulphide concentrate.
Tailings from the lead sulphide flotation will pass through rougher and three-stage cleaner flotation to produce zinc.
The final zinc and lead concentrates will be transported by road and exported via the Port of Guaymas to the Mexican smelters.
Ore from the small-scale trail mining is proposed to be processed at the San Javier sulphide flotation plant, located approximately 200km from the project area.
Azure has secured financing of A$2m required for the trial mining option from Deutsche Balaton, a major shareholder.
Infrastructure at Oposura project
The Oposura project can be accessed through the Hermosillo-Moctezuma highway (National Highway 14), followed by a 10km-long gravel road.
Power supply for the project will be enabled by constructing a 34kVA medium-voltage transmission line, to the north of the project. Water will be supplied from the aquifer located in Arenillas Valley, adjacent to the plant site.
Workers are proposed to be accommodated at a 220-person accommodation camp to be constructed to the north of the processing plant and mine.
Azure Minerals engaged consultancy firms CSA Global, Blue Coast Research, BPDT & Co, M3 Engineering, and Delia Patricia Aguayo Hurtado for the scoping study of the project.