Soil-rock geochemistry of Yanji area, Jilin Province: Based on geological formation

To explore the relationship between different geological formations and ecological environment in Yanji area for regional ecological management, this study analyzes the distribution and migration patterns of major and trace elements in the soil-parent material-bedrock of six geological formations in the low hilly area of Yanji City. The results show that the geochemical characteristics of various elements exhibit consistency within the soil-parent material-bedrock profiles of the six geological formations, demonstrating that the soil in the area was primarily originated from the in-situ weathering of local rock formations. The average chemical index of alteration(CIA)value for soil, parent material and bedrock is 61.62, indicating that the profiles across different geological formation units generally experienced lowintensity chemical weathering under cold and arid climatic conditions, with the CIA values consistently following the law of soil layer > parent material layer > bedrock layer. The study on the relative migration rates of elements reveals that, except for the Neogene basic volcanic formation, the chemical weathering in other geological formation units has largely completed the early-stage depletion of Ca and Na, and has preliminarily entered the mid-stage depletion of K.Among the trace elements in different geological formations, Nb shows varying degrees of depletion, while Y, Zr, Ce, La, Sr, Ba, Rb, and U exhibit either enrichment or depletion patterns influenced by weathering. Besides, Y, Zr, Ce, and La, as well as Sr, Ba, and Rb, respectively, display similar geochemical migration behaviors.