Formation mechanisms and significance of saline-lacustrine Se-rich soils in the Xining Basin

As shown by the investigation and analysis of the Se content in soils and rocks of the Xining Basin, the rocks and soils in the Paleogene Xining Formation and the Cretaceous Minhe Formation have the highest Se content, which makes them the major Se-rich parent materials of soils in the basin. By combining the paleogeographic data on the retreating process of the basin, it can be concluded that the Paleogene Xining Formation and the Neogene Guide Group were deposited from the arid and hot saline lacustrine facies to the humid and cool saline-freshwater lacustrine facies. The combined action of the saline lake boundary and the arid and hot saline-lacustrine environment, as well as the following transformation by landforms and water systems, contributed to the formation of the existing framework of saline-lacustrine sedimentary Se-rich soils in the Xining Basin. Such Se-rich soils enjoy the advantages of a low heavy metal content, a moderate Se content, and a high available Se content and thus are of great value in development and utilization.