Lithium- and boron-bearing brines in the Central Andes: exploring hydrofacies on the eastern Puna plateau between 23° and 23°30′S

Abstract

Internally drained basins of the Andean Plateau are lithium-and boron-bearing systems. The exploration of ionic facies and parental links in a playa lake located in the eastern Puna (23°-23°30′S) was assessed by hydrochemical determinations of residual brines, feed waters and solutions from weathered rocks. Residual brines have been characterized by the Cl − (SO 4 =)/Na + (K +) ratio. Residual brines from the playa lake contain up to 450 mg/l of boron and up to 125 mg/l of lithium, and the Las Burras River supplies the most concentrated boron (20 mg/l) and lithium (3.75 mg/l) inflows of the basin. The hydrogeochemical assessment allowed for the identification of three simultaneous sources of boron: (1) inflow originating from granitic areas of the Aguilar and Tusaquillas ranges; (2) weathering of the Ordovician basement; and (3) boron-rich water from the Las Burras River. Most of the lithium input of the basin is likely generated by present geothermal sources rather than by weathering and leaching of ignimbrites and plutonic rocks. However, XRD analyses of playa lake sediments revealed the presence of lithian micas of clastic origin, including taeniolite and eucriptite. This study is the first to document these rare Li-micas from the Puna basin. Thus, both residual brines and lithian micas contribute to the total Li content in the studied hydrologic system.

Fluid geochemistry of a deep-seated geothermal resource in the Puna plateau (Jujuy Province, Argentina)

“…Miocene-Pliocene volcanic complexes and extensive ignimbrite plateaus dominate the region that is characterized by arid climate and internally draining basins producing extended salt deposits (salar) and ephemeral B-and Li-rich salt lakes. Neogene volcanogenic polymetallic (Ag, Pb, Zn, Sn) sulfide ore deposits (some of them of world class) are also occurring, mostly being exploited by private and governmental companies (Lopez Steinmetz, 2016). Coira (2008) and Pesce (2008) reported the occurrence of several thermal fluids discharges in northern Puna, although little is known about their chemical and isotopic features.…”

“…Notwithstanding these promising results, the activity stopped after the drilling of few explorative, unproductive wells at Tuzgle-Tocomar zone (Giordano et al, 2013). The recent renewed interest for geothermal energy (Argentine National Laws n. 26.190/06 and n. 27.191/15), as well as the exploitation of other natural resources such as Li-rich deposits (Lopez Steinmetz, 2016), has intensified investigations in northern Puna aimed to evaluate, by means of geochemical and isotopic tools, the occurrence of thermal fluid reservoirs and their suitability for an exploitation in the years to come.…”

Hydrochemistry, Distribution and Formation of Lithium-Rich Brines in Salt Lakes on the Qinghai-Tibetan Plateau

“…Lithium in the salt lakes on the QTP may be derived from one or more processes [15,33,[62][63][64][65][66][67][68][69][70][71]:…”

“…The first two types of sources have been widely accepted by the geological community and supported by the Li-rich brines on the notable Andean salars. Weathering and erosion of widespread volcanic rocks and active or ancient hydrothermal springs related to volcanism contribute to the formation of Li-rich brines in most of the salars on the Central Andes [45,[68][69][70][71][72]. In contrast to widespread Cenozoic volcanic rocks in the Central Andes, there are restricted magmatic rocks on the QTP (Figure 1).…”

Volcanic and Saline Lithium Inputs to the Salar de Atacama

“…Its average concentration of 1400 mg/L exceeds the Li concentrations of other salars in the region by a factor of four, with the possible exception of Pastos Grandes in Bolivia, which averages 1062 mg/L [2,3] though its spatial extent is not reported. Hypotheses why Li becomes so enriched in brine within closed basins of the central Andes include indeterminate Li-rich rocks or clays, hydrothermal activity, an arid climate and tectonic subsidence [2][3][4][5][6][7][8]. These hypotheses are characteristic of the area in general, and not specific to the Salar de Atacama; thus, the reasons why the Salar de Atacama has become exceptionally enriched in Li requires a specific set of conditions.…”