Salt lakes on the Qinghai-Tibetan Plateau (QTP) are remarkable for Li-rich brines. Along with the surging demand of Li, the Li-rich brines in salt lakes on the QTP are of great importance for China’s Li supply. Previous studies reported the geological, geographical, geochemical signatures of numerous salt lakes on the QTP; however, conclusive work and the internal relationships among the hydrochemistry, distribution and geological setting of Li-rich salt lakes are still inadequate. In this study, major and trace (Li, B) ionic compositions of 74 Li-rich salt lakes on the QTP were reviewed. The Li-rich brines cover various hydrochemical types (carbonate, sodium sulfate, magnesium sulfate, and chloride types) and present horizontal zoning from the southwest to the northeast along with the stronger aridity. The Li concentrations and Mg/Li ratios in these salt lakes range from 23 to 2895 mg/L, 0.0 to 1549.4, respectively. The distribution of these salt lakes is close to the major suture zones. Geothermal water is proposed to be the dominant source of Li in the investigated salt lakes, while weathering of Li-bearing sediments and igneous rocks, and brine migration provide a minor part of Li. Four factors (sufficient Li sources, arid climate, endorheic basin and time) should be considered for the formation of Li-rich brines in salt lakes on the QTP.

The history of permanent human settlement in the high-altitude regions (>3000 m above sea level [masl]) of the Qinghai-Tibetan Plateau (QTP) is important in understanding human adaptation to this cold “Third Pole” region. The Qinghai Lake Basin was an important corridor used by prehistoric humans migrating to the inner QTP. Pastoralism is currently the most important means of sustaining permanent human settlement in the high-altitude regions of the QTP. However, the lack of reliable proxy measures reflecting prehistoric pastoral activities impedes our understanding of how pastoralism developed. The identification of coprophilous fungi in prehistoric cultural deposits may help refine the history of pastoralism. We collected 21 modern domesticated herbivore dung samples and 66 surface soil samples from the Qinghai Lake Basin for fungal spore analyses. We then evaluated how useful such analyses are for identifying grazing activities. Fifty-three samples were also collected from the JXG2 stratigraphic profile (∼10.0–0 ka; 3312 masl) for fungal spore analysis. Results indicate that low and stable values of the total concentration of coprophilous fungi were present from ∼10.0 to ∼5.5 ka. Concentrations gradually increased from ∼5.5 to ∼4.2 ka, significantly increased from ∼4.2 to ∼2.6 ka, and then increased dramatically after ∼2.6 ka. By combining these results with charcoal concentrations (>50 µm), lithic artifacts, bones and potsherds recovered from the JXG2 site, we infer that early pastoralism in Qinghai Lake Basin appeared between ∼6.0 to ∼5.5 ka and gradually intensified throughout the remainder of the Holocene as herding and farming gradually replaced hunting–gathering as the primary subsistence strategies. These results are supported by pollen records, archeological remains and historical records in the northeastern QTP.

Potash plays an important role in agricultural production. The Qaidam Basin (QB) in western China is a typical inland evaporite basin, which contains an abundance of K-rich brines, including shallow brines (i.e., surface brines and intercrystalline brines) in salt lakes and deep brines (i.e., pore brines and oilfield brines) in the strata. Significant studies on these brines have been reported; however, the integrated studies on sources of K, its distribution, and the sedimentary pattern of the two brine types are still inadequate. In this study, the K⁺ concentrations of sixty-four intercrystalline brines from the Qarhan Salt Lake (QSL), the largest playa in the QB, are presented. After combining those results with the major ionic compositions of river waters and deep K-rich brines, and the K⁺ concentrations of shallow brines in the QB, we concluded that: (1) The K of brines in the QSL is mainly from the high–flux K input by rivers which gain K from silicate weathering, while the “ancient Qaidam Lake” contributed little K to the QSL; (2) the large K flux supplied by rivers, the appropriate concentration degree, and the mixing of river waters and spring waters, cooperatively account for the highest K concentrations of brines in the QSL in the QB. The different river K recharges in different sections and isolated depressions are responsible for uneven K⁺ concentrations of brines in the QSL. (3) The deep brines are mainly distributed in the western QB. The K source of pore brines is from the interaction of pore water with the overlying evaporite layer. While the K in oilfield brines may be meteoric water, salt dissolution, the mixing of hydrothermal fluids, and the conversion of clay minerals to K-feldspar may consume K in the oilfield brines.