Tectosedimentary analysis of the Lithium-Boron Cauchari basin, Northwest Puna Plateau

ORNELA ESTEFANÍA CONSTANTINI; B. COIRA; C.I GALLI; C.R MONALDI

San Salvador de Jujuy

Simposio; 3rd International Workshop on Lithium, Industrial Minerals and Energy; 2016

The Cauchari salar basin is located in the Department of Susques, Jujuy province, in the Puna Plateau of Northwest Argentina (Figure 1). This region, together with Bolivian Plateau, concentrates many evaporitic deposits with a high economic potential, accumulated during the Neogene-Quaternary period. The most important lithium and borate deposits in South America are concentrated in the Central Andes.Approximately 15 Ma ago began the development of intermontane basins governed by extreme aridity conditions. The accumulation of evaporates and a functional internal drainage in Puna basins as a result of subsidence occurred in the Miocene [1] [2].The Puna constitutes an ?evaporitic province? with salars until deep levels and where in addition to having evapofacies of gypsum and halite have borates. Deposition of borates began at about 8 Ma ago and it is believed to be related to volcanic activity in centripetal drainage basins [3] [4].The Cauchari basin is characterized by continental deposits and age rocks upper Cenozoic. The largest lithium and borate accumulations are part of the Late Miocene, composed by different evaporitic and clastic units. There are two structural features keys in this region, high angle reverse faults north-south direction (formed by a horst and graben system) and guidance with directions northwest - southeast. The basement of Cauchari basin is composed by Ordovician deposits, Upper Mesozoic-Lower Paleogene Salta Group deposits, intensely deformed by tectonic activity in the region, controlled by meridional faults in north-south direction. On the western margin of Cauchari salar is the most extensive travertine platform in the Puna that retain features of ancient hot springs. This platform is associated with the fault which lifts up the Palaeozoic block. At the southern margin there are borates deposits of ulexite [1] [4] [5]. Some authors propose an environment and facies model of continental evaporites within a close basin, with a shallow groundwater level and a playa-lake environment with asymmetric Surface zonation overturned west. Other model proposed is a terrigenous salar like ?Silver Peak, Nevada?. This model happens on structural depressions restricted by depth.Until moment it is not known precisely the source providing Li and B in the Puna. Some authors have pointed to the hot springs as the main contribution and a number of secondary sources (lixiviation of the Cenozoic and the basement rocks) [1] [3] [6]. The Antuco thermal source (southern Cauchari Salar) collected all the elements permitting the formation of borate deposits in this region; with an active magmatic centre in proximity as is the Tuzgle, faults that allow the circulation of hydrothermal fluids in depth, active thermal springs with high concentrations of boron and lithium, powerful travertine deposits that show increased thermal activity in the past and favourable weather conditions for the accumulation of evaporates. [7] [8]The objectives of this work is to analyse the evolution of the Cauchari basin in the context of Andean tectonics, and obtain a characterization of clastic and evaporitic process, sedimentary facies of the saline system, stratigraphic controls, structural and sedimentary controls of surface and underground with the purpose of establish the tectonic control, lithium and boron distribution in the salar and the possible source areas. Establish the ion contribution which is generated by leaching of the lithology in the basin and establish the process and lithological paternal relation of lithium, boron and other elements of the brines. The proposal is to generate an evolution basin model, and in the future correlations with neighbouring areas.