Lithium brine exploration, resource/reserve estimation and mining focuses on hydrogeological techniques adapted for hypersaline solutions. The high variability in basin size/geometry, aquifer properties and brine chemistry, along with the fact that projects are in hyper-arid environments, cause technical challenges and undertaking independent reviews and due diligence requires a multi-disciplinary approach. Due diligences are focused on the following critical aspects.
Resource: brine volume and chemistry
Critical exploration data for resource definition include surface geophysics, geological core logging, specific yield, hydraulic conductivity and brine chemistry. The resulting geological model is composed of hydrostratigraphic units. Data quality and QA/QC procedures should be reviewed for brine chemistry, specific yield and hydraulic conductivity. Brine chemistry data should include not only lithium but also other key parameters that may negatively affect brine chemistry, such as magnesium, boron, sulphate and calcium. The robustness of the geological model and resource estimation relies on the 3D distribution of specific yield and brine chemistry throughout the hydrostratigraphic units.
Reserve: brine extractability
Critical parameters to assess brine extractability come from short-term and long-term hydraulic tests, both in the brine reservoir and surrounding freshwater aquifers. Additionally, long-term pumping tests (at least 30 days) with brine sampling should be performed to assess suitability of pumping rates for annual production at the expected commercial scale, assur freshwater availability according to process plant demand and evaluate risk of brine dilution in the long term.
Processing: process design suitability for brine chemistry
Brine chemistry should be carefully reviewed either by pre-evaporation or direct lithium extraction methodologies to assess the client’s decision. Afterwards, assessment of process design, flow diagrams, CAPEX and OPEX, among others, must be in line with freshwater demand/availability and long-term brine chemistry evolution from the reserve review.
Infrastructure: Li²CO³ production plan suitability
The designed and built infrastructure is reviewed for capacity and adequacy in relation to the project and its potential expansions. The facilities are analysed from the capacity of mining camps and potential for energy generation, to supply of raw materials and export logistics proposed for lithium carbonate.
Environmental and Social: feasibility assessment
Environmental and social input to due diligences on lithium brine projects is in line with international standards. Any inappropriate handling of environmental and social features can render a project unfeasible, regardless of the technical aspects. Critical features of these projects are scarce water availability for brine process demand, fragile ecosystems surrounding the salars and lack of proper social management plans.
