Argosy upgrades mineral resource estimate for Rincon lithium project

Lithium explorer Argosy Minerals (ASX: AGY) has announced an 18% increase to the original mineral resource estimate at its flagship Rincon lithium project, located within Argentina’s famed “lithium triangle”.

The new estimate of 245,120 tonnes of contained lithium carbonate equivalent was calculated from the results of 21 brine investigation holes drilled to depths of up to 147m in the south east of the Salar Del Rincon in the region’s Salta province.

It replaces the maiden estimate announced in June of 207,957t of contained lithium carbonate equivalent calculated from the results of an initial eight drillholes to depths of up to 102.5m.

Argosy said 100% of the resource is now in the higher-geological-confidence indicated category.

It added that the Rincon resource and brine aquifer remain open at depth with “excellent scope” for resource expansion from additional deeper drilling and continued tenement acquisitions.

Lithium-enriched aquifers

Prior to the new estimate, mineral exploration and test production bores were drilled into the brine-saturated aquifer underlying the Salar, at an average spacing of 950m for a total 1662 metres.

The bores delineated an aquifer containing hypersaline brine with total dissolved solids ranging between 310,000 milligrams per litre and 350,000mg/l.

The brine is enriched with respect to lithium, with concentrations ranging from 226mg/l to 487mg/l.

The aquifer sequence is reported to have a weighted mean average lithium concentration of 325mg/l, with a maximum recorded concentration of 490mg/l.

It is estimated the aquifer sequence within the project tenement boundaries, to a vertical depth of 102.5m, contains the upgraded estimate of 245,120t.

Argosy said further works to refine the hydrogeological model at Rincon will include longer-duration pumping tests to determine hydraulic properties of hydrostratigraphic units, changes in production grade over time and the optimal brine-abstraction rates.

Borehole magnetic resonance logging on some of the existing drill holes will aim to provide alternative estimates of porosity, specific yield and permeability.

The company will also conduct investigations at the interface between the eastern edge of the brine aquifer and adjacent alluvial and colluvial deposits; and develop a dynamic model using fieldwork data to simulate the aquifer’s long-term response to pumping.

Preliminary economic assessment

Argosy is fast-tracking the development of the Rincon lithium project, and will use the upgraded mineral resource estimate to proceed to preliminary economic assessment stage.

The PEA will include hydrogeological data, with life-of-mine modelling, production and brine pumping parameters, mineral resources and borefield details; capital and operating costs; details on processing and engineering works; and financial and marketing analyses.

In 2019, the company expects to commence ongoing, steady-state operations from a Stage 1 pilot plant to produce ‘battery grade’ lithium carbonate product and supply to potential off-take customers.

At mid-afternoon trade, shares in Argosy Minerals were down 8.00% to $0.230.