# Lithium Concentrations in Saline Brines of the Shu-Sarysu Depression
## 5 Discussion  
For the Shu-Sarysu drainage basin, the results from the analysis of the salt flats suggest that the most promising area for lithium is the salt brine deposits in the lower course of the Sarysu River. This observation provides support for the theory of dissolved alkali metals migrating along the Sarysu River and precipitating in its downstream regions, where extensive and numerous salt flats have developed. Furthermore, this area experiences additional input of near-surface water from underground aquifers through fractures, further elevating the mineralization levels. The potential horizons for the distribution of lithium brines are within the Neogene-Quaternary deposits, with a thickness ranging from 15 to 30 m.  
Table 1 displays the varying lithium (Li) concentrations in the six locations studied. In the Tampaly, Aktuz, Telekol, and Ashysor salt flats, not a single sample with a Li content equal to or greater than the minimum industrial values found in known deposits (5 mg/L) was identified (Figure 7) [13]. Meanwhile, in the Karakoin salt flats, Lower Sarysu sors, and Lower Shu sors, the percentage of samples containing lithium concentrations exceeding 5 mg/L amounts to 23%, 51.5%, and 11.8%, respectively, relative to the total number of samples collected from these salt flats. Notably, with higher lithium content, the Karakoin salt flat and the Lower Sarysu sors are of particular interest. Within samples collected from these salt flats, the concentration of lithium ranges from 10 mg/L to 60 mg/L, occasionally even reaching as high as 97.24 mg/L. The average lithium concentrations in the examined saline brine deposits of the Shu-Sarysu drainage are as follows: Karakoin--5.13 mg/L, Tampaly--1.7 mg/L, Aktuz--0.66 mg/L, Telikol--0.91 mg/L, Sarysu--14.1 mg/L, Ashysor--2.9 mg/L, and Shu--2.6 mg/L. In addition, there are soil samples with lithium concentrations exceeding 5 mg/L, namely 77.7% in Karakoin, 55.5% in Ashysor, and 37.5% in Lower Sarysu sors, in proportion to the total number of samples taken from each salt flat (Table 2) (Figure 8). Overall, the lithium concentrations found in soil samples are lower than those in water (brine) samples are. As previously noted, to ensure the quality control of the laboratory research results, 30 brine samples from the studied salt flats were sent to the chemical laboratory of the \"Scientific-Analytical Center\" in Almaty. These samples were analyzed using the ICP-MS method, and the lithium content in the brine samples was found to be 3.5 times higher than the results analyzed using the ICP-AES method at the \"Institute of Hydrogeology\" (Figure 9). The ICP-MS method typically provides higher accuracy due to its sensitivity and ability to correct for interferences, with an accuracy for lithium that can be within \(\pm\)1-2%. On the other hand, the accuracy of the ICP-AES method usually ranges within \(\pm\)2-5%, but it can be more affected by spectral interferences and matrix effects compared to ICP-MS. The accuracy limits of these methods do not explain such significant differences in results. Numerous factors could have influenced the results, including proper sample preparation, calibration, interferences, and corrections. Similar discrepancies in the results of analytical studies were noted in previous works. Upon reviewing a large number of publications that provide a quantitative assessment of lithium content in brine or salt flat solutions [3; 4; 14; 15; 16; 17; 18; 19; 20], it becomes apparent that none of them specifies the characterization or the name of the laboratory analytical methods used. The complete analysis reveals that the total mineralization in each brine sample falls in the range of 300-400 g/L (Table 3), which aligns with the mineralization levels observed in brines from deposits in the Andes, Tibet, Mongolia, and other regions [15; 16; 21; 22; 23; 24; 25]. Figure 8: Diagram of statistical data processing of analytical research results on lithium in soil samples of field seasons 2022–2023.