Something to consider when looking at the lithium subsector is that lithium brine “reserves” are noncompliant with Australia’s Joint Ore Reserves Committee and Canada’s National Instrument 43-101 standards, although some companies claim that their estimates are.
The fundamental problem is that existing codes for mineral resource and reserve reporting all apply to solid-phase minerals and are in need of revision to acknowledge the fact that the brine is fluid and mobile, and once extraction (i. e. pumping) starts, induced inflows and mixing may change the resource during the course of the project’s life.
Three parameters define a brine resource: the host aquifer’s geometry the aquifer’s effective porosity and the brine grade.
A company can determine an aquifer’s geometry by geophysical surveying and drilling.
For effective porosity, a company needs to combine downhole geophysics with laboratory work on samples. This is relatively easy in mature salars that infill with salt and allow generally good core recovery. But it’s much more complicated with less-mature salars with a sequence of unconsolidated sediments.
Determining brine grade requires that in-situ samples are collected for analysis, and ensuring that the sampling is truly of in-situ fluids.
Furthermore, to evaluate characteristics such as an aquifer’s behaviour over time, possible changes in chemistry over time and the recov-erable reserve, a company would need to develop a digital-simulation model of the aquifer with inputs of precipitation, surface-water inflows, groundwater inflows and evaporation existing for pre-development conditions and, once calibrated, the target pumping rate.
Only on completion of all this would a reserve estimate be possible.
The need to add to the lithium reserve reporting codes has been broadly discussed in the industry but not pursued, even though it is clearly desirable.
— Based in San Diego, the author is a geologist who has been involved in the lithium subsector globally since the early 1970s.
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