Ascendant has completed its initial NI 43-101 Feasibility Study (“FS”) for the Venda Nova deposit at Lagoa Salgada VMS Project in Portugal, based upon an updated Mineral Reserves and Resources Estimate.
Highlights of the 2023 Definitive Feasibility Study include:
- Post-tax NPV8% of US$147 million and 39% IRR
- Average annual payable zinc equivalent (“ZnEq”) production of 124 million lbs per annum over first 5 years
- Average All-in Sustaining Cost (“AISC”) of US$0.59/lb ZnEq over first 5 years
- Robust Average EBITDA of US$75.5 million per annum over the first 5 years
- Upfront capex requirement of US$164 million (including US$12 million of contingency)
- Inaugural NI 43-101 compliant Proven and Probable Reserves in the North Zone and South Zones of 14.6Mt at an average NSR of US$66.1/tonne
- Updated NI 43-101 compliant Mineral Resource of:
- North Zone: 8.9Mt at 10.52% ZnEq Measured and Indicated and additional Inferred Resources of 0.5Mt at 6.62% ZnEq
- South Zone: 10.0Mt at 1.22% Copper Equivalent (“CuEq”) and additional Inferred resources of 8.1MT at 1.16% Cu Eq.
- Fulfilled option requirement to deliver 80% indirect ownership in the Lagoa Salgada Project;
- Metallurgical results confirm strong metal recoveries and saleable concentrates
- Optimization Program commenced to enhance NPV, IRR and operational efficiencies targeted for completion by year end.
Updated Minerals Reserves and Resources Estimate
Table 1. below outlines the initial NI 43-101 Proven and Probable Mineral Reserves Estimate prepared by IGAN Ingenieria upon which the FS was based. Table 2 provides the updated Mineral Resource Estimate, prepared by Micon International Limited, (“Micon”) identified for the Lagoa Salgada project to date. Infill drilling in 2022 focused upon upgrading sufficient high-grade mineralization in the North Zone and part of the mineralization in the South Zone to the Measured and Indicated categories to support the completion of the FS.
Future drilling is expected to add additional Resources as the project moves forward to extend the overall mine life and it should be noted both the North and South zones remain open to future expansion along strike and at depth for future exploration. In addition, several regional exploration targets have been identified for future exploration work to further increase the known mineral resources on the property, thereby extending the overall mine life and/or potentially supporting a future expansion.
The estimated Proven and Probable Reserves total 14.6 million metric tons (Mt), with 7.0Mt in the North Zone having an NSR of 84.1 $/t, and 7.6Mt in the South Zone with an NSR of 49.6 $/t, sufficient to support an initial mine life of 14+ years based upon a throughput rate of 1.2Mtpa through the plant as outlined in the FS. Reserves were defined using an NSR calculation based upon current metallurgical recoveries, payability, treatment charges and mining methods.
The project has converted 77% of its Measured and Indicated resources into reserves: additionally there are 0.5Mt at a grade of 6.62% ZnEq in the North Zone and 8.13Mt at a grade of 1.16% CuEq in the South Zone of Inferred Resource. Additional drilling is required to upgrade these additional resources to the Measured and Indicated categories.
Mining
In line with previous studies, the mine is designed using a single access ramp from surface and will target the extraction of ore from the North and South Zones at a rate of 1.2 million tonnes per annum (“Mtpa”).
Mining will be undertaken by targeting the various sub domains within the ore deposit to maximize metallurgical recovery. As with most VMS type deposits, the sub domains reflect a precious metal rich gossan layer above a Massive Sulphide layer (further divided into a Transition and Primary layer) and a layer of stockwork mineralization each with its own metallurgical characteristics. The mining methods defined are a combination of transverse sublevel stoping and cut & fill. Paste backfill is to be used for both mining methods to maximize ore recovery and productivity while minimizing surface tailing disposition. The initial years will focus on mining the higher-grade gossan and massive sulphide zones in the North Zone, followed by the South Zone as underground access is developed in the early years of the operation to the South zone. Mining will be conducted using an owner operated electric fleet which will reduce operating costs.
Figure 2. Underground Mine Design
Metallurgy
Metallurgical test work was completed by Grinding Solutions (“GSL”) in Cornwall, UK. Confirmatory test work was developed by Maelgwyn Mineral Services, South Africa to confirm metal recoveries and saleable concentrates have been achieved in principal domains. Further testing is required to confirm and improve on current results as fully optimized circuit adjustments are developed. The Company notes that its consultants have indicated that the actual performance of operating mines in the region have typically seen an improvement in concentrate quality once an industrial scale operation is in production as compared to lab testing.
The approach to flowsheet development was to prepare representative master composites for each ore type, then proceed through open circuit to identify and optimize flowsheet conditions and reagent schemes. Locked cycle tests were then conducted on principal master composites to demonstrate the anticipated overall metallurgical performance within a closed circuit.
Tests were completed on blends of Primary Massive Sulphide (PMS), Stockwork (STW), Gossan (GO), Transition Massive Sulphide (TMS) and Stringer (STR) ores to allow comparison with individual composite results and to assess the viability of co‐processing the ore types.
Mineralogical assessments were undertaken to provide information to refine the comminution/beneficiation process during optimization, and to provide reasonable expectations for metallurgical performance versus mineral liberation and association within each ore type. Samples from various open and locked cycle test products were used to characterize final concentrates and tailings.
The developed metallurgical models were applied to mine production schedules as part of the financial modelling process. The resulting average recoveries over the life of the mine (LOM) are presented in the table below:
Table 3. Achieved Recoveries by Metal and Domain
Processing
The mineral treatment plant is based on industry standard methods and will mainly consist of different process areas where the mineral will be crushed, ground, and then fed to several flotation processes where Cu, Pb, Zn and Sn concentrates and Au/Ag dore bars will be produced. Other than crushing, grinding, dewatering and auxiliary services, common to all mineral domains, the remaining process areas will be configured depending on the mineral domain being processed. The mined material goes through a grizzly feeder and primary jaw crusher, and then onto a grinding circuit which consists of a SAG mill, ball mill, and vertical mill in a closed circuit with hydrocyclones. The material is discharged into a vibrating screen, with rejected pebbles recirculated to a pebble crusher.
Grinded material will feed the copper and lead flotation circuit, that includes aeration and conditioning tanks, rougher cells, regrinding mill, and cleaning stages. The circuit can produce bulk or separate Cu and Pb concentrates depending on the mineral domain being processed. The zinc flotation circuit, downstream process, consists of conditioning tanks, rougher cells, regrinding mill, and cleaning stages.
Zinc flotation tailings, feed the sulphide flotation circuit to remove sulphides before concentrating tin minerals. It includes conditioning tanks, rougher cells, and cleaner stages. Rougher tailings flow to the next area, while the concentrate is pumped to the tailings management area. The tin recovery circuit will consist of flotation and gravimetric concentration technologies. Flotation includes conditioner and aeration tanks, rougher and cleaner stages, with intermediate tin concentrate being processed using multi-gravity separators to increase the final tin grade. A summary Flowsheet is provided below.
Figure 3. Simplified Process Flow Diagram
Infrastructure
The Lagoa Salgada Project will be developed on a greenfield site located in close proximity to the Grândola municipality, in the Setúbal district, which benefits from well-established infrastructure, including road and rail transport, power, and water supply services. Transportation of supplies will be facilitated by trucks from Portugal or Spanish locations, while concentrate products will initially be shipped to the Sines port by road (47km) and subsequently by ship to final destinations.
The project site will have a compact layout that incorporates essential components such as the tailings storage facility, ore and waste dumps, water treatment infrastructure, and various buildings, including administration, warehouse, laboratory, gatehouse, and mobile equipment workshop. The processing facilities will consist of a primary crusher building, ore stockpiles on the ROM pad, a mill building, and a paste plant building.
The mine will be accessed via a portal and the ore will be brought to the surface and stored as stockpiles, while waste stockpiles will be utilized for constructing the embankments of the Tailings Storage Facility.
The mine plan outlines the processing of 14.8 Mt of ore and the generation of 1.9 Mt of waste rock. After accounting for concentrate and underground backfill, a total of 11.3 Mt of tailings, along with 1.0 Mt of development rock, will be deposited in the TSF.
Figure 4 Site Layout
Zn, Au, Ag, Pb, Cu, Sn
