# Lithium Concentrations in Saline Brines of the Shu-Sarysu Depression
## 3 Materials and Methods  
The regional research method comprises two phases: the pre-field and field periods. During the pre-field phase, the study area's geomorphology, hydrogeology, and geochemistry were examined. Satellite images (multispectral and radar) from the Landsat-8, Maxar, Sentinel, and RADARSAT-1 satellites were previously downloaded from the website [[https://eos.com/landviewer/](https://eos.com/landviewer/)]([https://eos.com/landviewer/](https://eos.com/landviewer/)) accessed on 10 June 2023. These satellite images were interpreted to assess parameters such as water content, salinity, preliminary composition, and the geomorphology of saline brine deposits in the lower courses of the Shu and Sarysu, including the large salt flats Karakoin and Tamgaly. Interpretation of the Sentinel satellite images provided information regarding the content of water in salt flats, while the combination of Landsat and RADARSAT-1 images effectively revealed the geomorphological characteristics of the study region (Figure 4). Subsequently, the field period involved geochemical sampling of saline brine deposits to assess lithium mineralization levels in salt lakes, salt flats, and salt domes. Geochemical surveys were conducted using both hydrogeochemical and lithochemical sampling techniques. The former method examines surface water composition to identify hydrogeochemical anomalies that indicate the presence of elevated lithium concentrations in shallow waters and brines, such as salt lakes, wet salt flats, and flowing wells. For sampling, a permanent layer of halite, including a temporary layer, approximately 10-15 cm thick, was initially exposed. Subsequently, a well with a diameter of 150 mm and a depth of 1 m was manually drilled into the silt layer. The brine was then allowed to settle in the well  
Figure 3: Hydrogeological Cross-Sections at the Junction Zones of the Shu and Sarysu Artesian Basins, illustrating Brine Discharge into the Overlying Aquifer of the Platform Cover [10]. 1—Contour of the distribution of the aquifer complex in Paleocene–Middle Eocene deposits; 2—direction of groundwater flow; 3—salt flats; 4—boundary of different types of groundwater; 5—tectonic faults. for 5 min, after which a sample of brine was collected, and sediment was retrieved from the bottom of the well. The latter investigates the distribution of chemical elements in sediments and soils to identify halos that indicate the concentration of lithium beneath the surface. During the field-work periods, manual drilling was employed for brine sampling, resulting in a total of 221 samples, including 166 brine samples and 47 soil samples collected from the bottom of the drill-hole. In the lower course of the Sarysu River, numerous small sons (shallow salt flats) and salt flats are present, and samples of water and soil were collected from this area. The Sarysu Site covers approximately 90 square kilometers, and a total of 75 samples were collected (Figure 5). The analysis involved quantifying the lithium levels in water (brine) samples obtained from the salt flats in the Shu-Sarysu depression. This assessment took place at the Chemical Laboratory of the Ahmedsfin Institute of Hydrogeology and Geoecology, utilizing the ICP-AES method. To ensure the quality of the analysis, 30 water (brine) samples were sent, along with soil samples, to the Chemical Laboratory of the Scientific Analytical Center (Almaty, Kazakhstan) (Tables 1 and 2).