Lithium Argentina AG

Figure 6.10 Caucharri-Olaroz Watershed

Note:* black dot with a number beside it = meteorological station, red square = town.*

The brines from Cauchari are saturated in sodium chloride with total dissolved solids (TDS) on the order of 27% (324 to 335 g/L) and an average density of about 1.215 g/cm 3. The other primary components of these brines are common to brines in other salars in Argentina, Bolivia, and Chile, and include potassium, lithium, magnesium, calcium, sulphate, HCO 3, and boron as borates and free H 3 BO 3.

A Janecke Projection comparing the chemistry of several brine deposits is shown in Figure 6.11. This type of figure can be used as a visualization tool for mineral crystallization. The diagram represents an aqueous five-component system (Na+, K+, Mg++, SO 4=, and Cl–) saturated in sodium chloride. The aqueous system can be represented in this simplified manner, due to the higher content of the ions Cl–, SO 4=, K+, Mg++, Na+ compared with other elements (e.g., Li, B, Ca). In Figure 6.11, each corner of the triangle represents one of three pure components (Mg, SO 4 and K 2), in mol%. The sides of the triangle represent sodium chloride-saturated solutions, with two reciprocal salt pairs (MgCl 2 + Na 2 SO 4), (Na 2 SO 4+KCl) and a quaternary system with a common ion (MgCl 2+KCl+NaCl).

The inner regions of the diagram show expected crystallization fields for minerals precipitating from the brine. Since the brines are saturated in NaCl, halite precipitates during evaporation in all the cases. In addition, the Cauchari brine is predicted to initially precipitate ternadite (Na 2 SO 4). The brines of Guayatayoc, Silver Peak, Hombre Muerto, Olaroz, and Rincon would initially precipitate glaserite (K 3 Na(SO 4)2). Atacama, Uyuni, and Salinas Grandes brines would initially precipitate silvite (KCl).

In addition to the primary minerals indicated in the diagram, a wide range of secondary salts may precipitate from these brines, depending on various factors including temperature and dissolved ions. The additional salts could include: astrakanite (Na 2 Mg(SO 4)2·4H 2 O), schoenite (K 2 Mg(SO 4)2·6H 2 O), leonite (K 2 Mg(SO 4)2·4H 2 O), kainite (MgSO 4·KCl·3H 2 O), carnalite (MgCl 2·KCl·6H 2 O), epsomite (MgSO 4·7H 2 O), and bischofite (MgCl 2·6H 2 O).