Xuxa lithium project involves the construction of an open-pit mine and lithium concentrator in the Minas Gerais state, Brazil.
The feasibility study (FS) for the project was completed in October 2019 and paved the way for the detailed engineering work. Sigma filed an independent FS technical report for the Xuxa mine in November 2019.
The study indicated an average annual production rate of 220,000t per annum (tpa) of battery-grade 6% lithium oxide concentrate with low impurities over an estimated mine life of 9.2 years.
The mine is 100% owned by Sigma Lithium Resources. The project is supported by non-binding offtake agreements for the supply of 100% of the production from the plant for five years. Sigma signed an agreement with Mitsui to provide offtake rights over a significant amount of production in exchange for a $30m pre-payment facility to fund the development of the Xuxa mine.
The construction of the lithium concentration plant is expected to begin in March 2020, while the production start is scheduled for 2021.
Xuxa lithium project location
The Xuxa lithium project is located in the Grota Do Cirilo property of Vale do Jequitinhonha in Brazil. The Grota Do Cirilo property has ten mining concessions and Xuxa is the first deposit to be developed as part of the project.
The deposit is located between the cities of Araçuaí and Icinga in the state of Minas Gerais.
The Xuxa plant will be located 1.7km away from the north Xuxa mine open-pit and 2.3km from the south open-pit.
Xuxa lithium project geology and mineralisation
At the Xuxa deposit, the pegmatite is found on the surface to the south and at depth and comprises large crystals of spodumene.
The pegmatite at the location measures 1.7km-long and 14m-16m-wide. It strikes northwest to southeast dipping approximately 50° west.
As of 2019, the Xuxa lithium project is estimated to contain proven and probable mineral reserves of 13.79Mt graded at 1.46% of lithium oxide (Li₂O).
Mining at Xuxa lithium project
The Xuxa project will be a 1.5Mtpa spodumene ore mining and lithium concentrate processing operation. It will employ a conventional open-pit mining method using hydraulic excavators and haul trucks. The project will include the development of two separate pits and four waste piles to stock waste rock from the open pits and plant residue.
The engineered pit designs have provision for haul road, pit slopes with geotechnical berms, smoothed pit walls and proper benching configuration.
Trucks will be used to load excavated material that will be hauled to either the run-of-mine (ROM) pad or the waste piles.
The mine will employ controlled blasting (pre-splitting) to enhance recovery and reduce dilution. The process will involve the blasting of fresh rock on 6m benches for ore domain and 12m benches for waste domain.
Xuxa lithium project processing details
The ore from the deposit will be processed through a dense media separation (DMS) plant. The plant will include a three-stage conventional crushing and screening circuit and a two-stage DMS circuit for the coarse fraction. Mica is removed from the feed via up-flow classification before DMS processing.
The material is sent to the two-stage DMS circuit for coarse fraction, and two other circuits for fines and ultra-fines fraction. A magnetic separation step will be incorporated to enable separation of the fine size particles.
The hyperfine fraction with the waste will undergo thickening, filtration (belt filter) and dry stacking. The plant will also use optical sorting and / or magnetic separation techniques on the concentrate. The tailings will be transported using trucks for co-disposal with waste rock.
The processing capacity of the plant can be increased to 3Mtpa by installing an in-house crushing circuit.
The DMS plant will have a throughput of 220,000tpa of minimum 6.0% Li₂O concentrate with less than 1% of Fe₂O₃ and 0.55% of alkalines.
Xuxa lithium project infrastructure
The plant will receive power from a hydroelectric plant and Brazil’s green electricity grid.
It will recycle over 90% of the water used for processing and use dry-stacking technology to handle tailings from the concentration plant. The project holds a water usage licence that permits the use of 150m³ of water an hour.
Roads and office building at the site form part of the existing infrastructure.
Contractors involved
Sigma contracted Primero Group Americas, SGS Geological Services, Worley Parsons and GE21 Consultoria Mineral for preparing the FS technical report for the project.
MCB (Deswick Brazil) completed the mine plan portion of the FS, while Roskill provided market analysis services. 3S/DF Spain prepared the tailings and mine waste storage design.
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