African mineral sands producer Base Resources, listed on the ASX and AIM, has completed a Definitive Feasibility Study (DFS) on its Toliara project in Madagascar. According to Colin Bwye, Executive Director Operations and Development of Base Resources, the DFS confirms the company’s view that Toliara is “a world class mineral sands development opportunity.” A final investment decision is planned for September this year.
The DFS outcomes closely align with the Pre-Feasibility Study (PFS) outcomes released in March 2019 and confirm a post-tax/pre-debt (real) NPV10 of US$652 million and an average revenue to cost ratio of 3,15 over the initial 33-year mine life. Stage 1 capex to establish a 13 Mt/a mining processing operation is estimated at US$442 million and Stage 2 capex, which will increase production to 19 Mt, at US$69 million.
A dozer trap mining unit. This is the mining method that will be employed at the Toliara project.
“In the first 26 years of full production, the Toliara project is expected to produce an average of 814 kt of ilmenite, 55 kt of zircon and 7 kt of rutile annually, over a period when a global supply deficit of titanium dioxide feedstocks and zircon is expected,” comments Bwye. “This production profile, combined with a highly competitive revenue to cost of sales ratio, will generate estimated average annual free cash flows of US$140,2 million over these years.”
The Managing Director of Base Resources, Tim Carstens, makes the point that Toliara, if it goes ahead, will be the first large-scale mining investment in Madagascar in almost a decade. “With the application of the Base Resources’ development model, as demonstrated with the Kwale Operation in Kenya, the Toliara project is expected to have catalytic impact,” he comments. “It will create transformational opportunities for our communities, economic stimulus for the Toliara region and a flagship foreign investment for the government that is forecast to directly generate in excess of US$1 billion in government revenue and community development expenditure over the 33-year mine life.”
The Toliara project is located in south-west Madagascar, 45 km north of the regional port town of Toliara, 18 km inland from the coast, and approximately 640 km south-west of Antananarivo, the capital city. The project is based on the the Ranobe deposit, which comprises a single continuous body of mineralisation approximately 20 km long, 1,5 to 4,5 km wide and 3 to 60 m in thickness. The heavy mineral (HM) mineralisation (including ilmenite, rutile and zircon) extends from the surface.
The deposit has three mineralised units. These are the upper sand unit (USU), a well-sorted, fine-grained unconsolidated aeolian sediment mineralised unit; the intermediate clay sand unit (ICSU), a thin unit of high slime content; and the lower sand unit (LSU), a medium-grained quartz sand mineralised unit with moderately low slimes content. The LSU onlaps the limestone (LST) basement. The deposit thickness generally increases to the west.
The JORC-compliant mineral resources estimate stands at 1 290 Mt at 5,1 % HM and 6,4 % SL, including 790 Mt at 5,8 % HM in the measured and indicated categories. The estimate is unchanged from the PFS. The JORC-compliant ore reserves estimate stands at 586 Mt at 6,5 % HM.
Base Resources is an experienced mineral sands miner. It acquired the Kwale mineral sands project in Kenya in 2010 and, over the ensuing three years, funded, engineered, constructed and commissioned the project, which is now a very successful mineral sands mine. It is hoping to repeat this experience with Toliara, which it acquired in early 2018. The company subsequently advanced the project rapidly, completing a concept study and the PFS by March 2019.
As detailed in the DFS, the Toliara project will be implemented in two stages following a nine-month Early Works/Feed programme to take into account higher ore grades in the early years. Over its 33-year life, it is expected to deliver approximately a combined 840 kt/a of chloride ilmenite, sulphate ilmenite, slag ilmenite, zircon and rutile.
Stage 1 consists of the engineering, procurement, construction and commissioning of Heavy Mining Equipment (HME), a Dozer Mining Unit (DMU), a 1 750 t/h wet concentrator plant (WCP) and a 150 t/h mineral separation plant (MSP). Also to be constructed in Stage 1 are various ancillary works such as a camp, a power generation facility, a haul/access road and bridge, an export facility storage shed and a jetty, and a multi-buoy mooring (MBM) facility and ship loader.
Stage 2 commences four years after initial production and includes the addition of a second DMU (identical to DMU1), a second 825 t/h WCP, additional HME and an upgrade of the power plant capacity by 30 %. The borefield will be expanded with the addition of two boreholes and the camp will be enlarged with the addition of an 18-room dormitory.
The selected mining method is conventional dozer trap with in-pit tailings deposition, enabling a short three to four-year cycle from initial land clearing to final land rehabilitation. Mining will involve three D11 bulldozers feeding a DMU to deliver 13 Mt/a to the WCP in Stage 1 before increasing to 19 Mt/a in Stage 2, with the addition of a second DMU and a single D11 bulldozer for the remaining mine life.
It is envisaged that an existing Kwale DMU built by Piacentini & Son will be refurbished and shipped to Toliara for Stage 1. The same company will be commissioned to supervise the DMU installation at Toliara as well as supply the second DMU in year 4. Each DMU is designed to be relocatable (using D11 bulldozers) and it is anticipated that relocation will occur every two to four weeks.
Run of mine feed (ROM) enters the DMU through a grizzly (400 mm screen), passes up the DMU conveyor which discharges to a slurry area where water is added, and then screened at 4 mm. The screen undersize is pumped to the WCP. Oversize is disposed of in the pit void.
Coarse tailings (quartz sand) separated by the WCP is pumped, initially to an out of pit storage facility and later to the mining pit void where a moveable tails stacker de-waters the slurry. Water is recovered and pumped back to the WCP. Sand is stacked to a height approximating the planned finished surface level and then formed into fine tails evaporation ponds by bulldozer.
Flocculated clay tailings (fine tailings) from the thickener at the WCP are pumped to the evaporation ponds built on coarse tails. Initially, until enough in-pit coarse tails area is available, some ponds will be constructed on ore and the dried tails removed to allow subsequent mining. The tails ponds will be filled to a depth of approximately 1,5 m and when dry the clay will be about 0,4 m thick.
Describing the landform reconstruction process, the DFS says the desiccated fine tails are worked by bulldozer into the coarse tails to make a nominal 2 m thick water retention layer at the surface, graded into final landform. Stockpiled topsoil is then placed on top using FELs, dump trucks and dozers or graders, following which the area will be ready for rehabilitation. The process from scrub clearing to final rehabilitation is expected to take 3-4 years.
In terms of processing, the flowsheet adopted for the WCPs uses proven spiral technology to produce a HMC grade above 90 %. The robust three-stage spiral plant design is based on bulk sample testwork conducted at Mineral Technologies’ metallurgical facilities and caters for the range of heavy minerals grades within the Ranobe deposit.
HMC from the WCP is pumped to the MSP. This will be fed at rate of 150 t/h, with the process being decoupled from the mining operation by an HMC stockpile which buffers changing ore grades and differing plant run times. Ilmenite (sulphate, chloride, slag), rutile and zircon final products will be produced at the MSP via a six-circuit flowsheet. Recoveries of 94,6 % ilmenite, 79,4 % zircon and 58,4 % rutile are anticipated. Final products will be stored in 1 000 t bins (350 t for rutile) with additional site storage provided for three ilmenite products (two weeks’ production).
A tall building (approximately 50 m) design has been adopted for the MSP with multiple machine floors to reduce operating cost (by utilising gravity to reduce materials handling equipment and drives). The MSP is fixed for the life of mine and all major mine infrastructure will be located at the MSP site (including power generation, administration, workshops, stores and camp).
In terms of infrastructure, Toliara is not particularly well served and the project scope addresses this through building a 45 km-long dedicated product haulage and access road (including a new 630 m long concrete bridge over the Fiherena River), an export facility, a power plant, a borefield for water supply and a permanent camp for expatriate and non-local skilled personnel (able to house 263 operational people and the 630 people expected during construction).
It is envisaged that power for the mine site will be supplied by an Independent Power Producer (IPP) with generation being based on a hybrid HFO, solar PV and battery storage system located near the MSP and camp. Stage 1 installed power is 23,5 MW with this increasing to 29 MW in Stage 2.
Regarding the construction phase, the DFS says that the construction effort will be spread over a wide geographic area covering the MSP, WCP, mine infrastructure, road, bridge and export facility. These works will be performed by multiple civil, structural, mechanical and pipework (SMP), electrical and instrumentation (EI) and marine contractors, with a workforce peaking at 1 629. It is currently envisaged that Stage 1 will be implemented over 26 months from October 2020 to November 2022 and Stage 2 between September 2025 and September 2026.
Photos courtesy of Base Resources