Summary:
The Carachi Pampa Basin is a hydrologically closed basin made up of lacustrine and alluvial sediments—gravels, sands, silts, and clays—with episodic volcanic deposits including ignimbrites, tuffs, and basalts. The basin is bounded to the east and west by north-south trending mountain ranges formed by thrust faulting. These ranges expose basement sequences that rise to elevations of about 5,100 meters above mean sea level. The Cerro Blanco pyroclastic complex lies to the south and is the main source of ignimbrites and tuffs. The Antofagasta de la Sierra and Cerro Galán volcanic complexes define the northern and northeastern highlands. Eastern ranges consist of crystalline Precambrian basement rock, sloping gently down to the basin floor.
The Carachi Pampa Basin spans 9,494 km² and is an arid, closed basin composed of interbedded lacustrine and alluvial sediments—gravels, sands, silts, and clays—with lithiumenriched brine filling pore spaces to depths exceeding 600 meters below ground surface (“m bgs”) in the central resource area.
• Groundwater flows towards the salar, the basin’s lowest elevation point, where discharge occurs through evapotranspiration, concentrating mineral-rich brine.
• A freshwater wedge overlies the brine in the north and northeast, where most groundwater enters the basin. Minimal freshwater exists in the central resource area, which hosts the planned extraction wellfield.
• Pumping tests confirm favorable hydrogeological conditions in proposed production zones (200–400 m bgs), with Unit B sands exhibiting hydraulic conductivity of 2–3 m/d. Deeper sands in Unit C average around 0.5 m/d.
• Fine-grained lacustrine deposits, particularly in the upper 200 m, limit vertical hydraulic connectivity between shallow aquifers and deeper production zones.
• Over 300 core samples analyzed by Geosystems Analysis using the Rapid Brine Release (RBR) method. More than 220 drainable porosity tests show averages of 7–8%, with fine sands at ~8%. BMR surveys indicate a 7.5% median value.
• Injection tests (12, 15, and 31 days) validate the feasibility of infield injection for spent brine disposal, supporting pressure maintenance and reducing risks of subsidence or changes to surface water bodies.
• Spent brine injection must balance proximity (for effective pressure support) and distance (to prevent dilution).
• Injection into western alluvial fans may mobilize lithium-rich brine toward downgradient extraction wells. Pressure changes propagate faster than brine movement, which takes years.
• Brine chemistry is consistent laterally and vertically. In the central salar, two long-term pumping tests recorded average lithium concentrations over 260 mg/L, with a 31-day test averaging over 270 mg/L.
Surface geophysics identified conductive brine-saturated sediments. Passive seismic data revealed basin depths of 700–800 meters in the western resource area. Contrast in velocities reflects the boundary between loosely consolidated basin fill and shallower volcanic facies. It aided to delineate zones of brine, brackish water, freshwater, and dry sediments, and added to the understanding of regional groundwater and salinity distribution.
Groundwater flows centripetally toward the salar where it discharges via evapotranspiration, concentrating the lithium brine.
• Lithium-enriched brine fills sediments to depths >600 m in the central resource area.
• Over 220 drainable porosity tests show 7–8% average in salar lithologies; BMR confirms 7.5% median. Alluvial fans have higher porosity (~20%).
• The freshwater wedge is thickest in the north and northeast. Little to no freshwater exists in the central salar which reduces dilution risk.
Dimensions
The lateral extent of the resource has been defined by the boundary of the Company’s properties, the outline of the Kachi volcano and the range of mountains to the west. The brine mineralisation, as defined by current total resource, covers approximately 274.8 km2.