Junior explorer Lake Resources (ASX: LKE) has unveiled a maiden resource estimate of 4.4 million tonnes contained lithium carbonate equivalent and 30mt of potassium chloride at its large-scale Kachi lithium brine project in the Catamarca province of Argentina.
Based on the results of 15 drill holes (7 diamond and 8 rotary), the estimate comprises 1mt of lithium carbonate equivalent in the indicated category and 3.4mt in the inferred, with a resource depth of around 400 metres below ground level in porous, permeable sediments.
Contained within the estimate total is 188,000 tonnes of lithium metal classified as indicated and 638,000t classified as inferred.
There is also a total resource of 3.5mt of potassium indicated, and 12.5mt of potassium inferred.
The brine-bearing sediments remain open at depth and laterally, and Lake said there is opportunity for resource expansion from additional deeper drilling and an extension of the exploration area.
“Our team advanced [drilling] activities within 12 months on an undrilled project, defining a large resource and locating a project which stands alongside the largest lithium projects in Argentina,” said Lake managing director Steve Promnitz.
“We [plan to] expand the resource with more drilling and move into a pre-feasibility study using conventional and a direct extraction technology which indicates high recoveries, low costs and a reduced time to production.”
The Kachi project, situated over 170,000 acres in the Catamarca province, comprises 36 mining leases owned by Lake’s Argentine subsidiary, Morena del Valle Minerals SA.
The leases are held over the centre and southern extension of the salt lake at Kachi in the lowest point (around 3000m altitude) of a drainage area approximately 6800 square kilometres in size and reported to be larger than most basins producing lithium brine.
A maiden exploration target released for Kachi in November showed potential for between 8mt and 17mt of LCE over an equivalent area of 20km x 15km, and based on containing brines from near surface to 400m depths within approximately 13 cubic kilometres of brine (or 13,000 gigalitres).
The maiden resource estimate covers a small portion of this total exploration target, and is centred on the western part of the basin.
To date, the company has drilled 15 brine investigation holes in the previously-untested salt lake to depths of up to 403m across principal target areas of the Kachi salt lake, revealing thick, permeable, sand-dominated sediments which are expected to continue below current drilling depth limits and beyond the lake’s surface dimensions.
Surface samples with positive lithium results in brines have been explored at depth during drilling and geophysics activities.
Drilling returned positive lithium values in the southwest of the project, while passive seismic geophysics suggested the basin is the deepest with brine extending under cover to the south.
In May, Lake confirmed the significant scale of the Kachi basin after it encountered near surface brine in “numerous horizons”.
Brine vs hard rock mining
Lithium brine projects are fundamentally different to hard rock mining projects as the lithium is dissolved in brine, which is hosted in pore spaces within sediments.
During the exploration stage, brine must be sampled for resource estimation in a representative way to minimise the potential for contamination between sample intervals.
Brine will flow into the drill hole as it is advanced.
At Kachi, brine sampling was carried out using a different methodology for each drilling type, with varying levels of confidence in the sampling.
Sampling methods included bailer, drive point and installation of production test bores.
Earlier this month, Lake announced it had partnered with lithium extraction company Lilac Solutions to advance a rapid, low-cost method for direct extraction of lithium from Kachi brines.
The process aims to enhance the grade, reduce the lead time to production, lower operating costs and significantly increase recoveries.
“The massive potential of this lithium brine is impressive,” Mr Promnitz said.
“To use the analogy of the contained fluid in Sydney Harbour, this [project] is equivalent to twenty five times that volume and the resource estimate only covers a small portion of this total potential.”