This paper is the result of environmental geological survey engineering.

Objective Clay minerals play a crucial role in soil quality regulation. Identifying the clay mineral characteristics of farmland soil in arid oasis areas is of great significance to soil quality control and agricultural development.

Methods This study focused on the farmland soil in the arid oasis area of the Kaidu−Kongque River Basin, Bayingolin Mongolian Autonomous Prefecture, Xinjiang, and explored the characteristics of clay minerals composition, provenance evolution, soil−forming climatic conditions and their influence on soil quality through systematic analysis methods including X−ray diffraction pattern analysis, correlation analysis, triangular diagram analysis and weathering index analysis.

Results The dominant clay mineral types in the study area are 2:1 illite, illite/smectite mixed−layer minerals, and chlorite, with a minor presence of kaolinite. The evolution sequence of the clay minerals, which originate from granite, is illite→illite/smectite mixed−layer mineral→chlorite and kaolinite. The illite crystallinity (IC value) ranges from 0.35 to 0.62, with an average of 0.44. The chemical alteration index (CIA value) ranges from 51.29% to 62.57%, averaging 58.24%. The compositional variation index (ICV value) ranges from 1.09 to 3.69, averaging 2.65. These indicators suggest a pedogenesis environment with low temperatures, aridity, and relatively weak weathering intensity. The total clay mineral content in the study area shows a positive correlation with soil nutrients and heavy metal elements.

Conclusions The clay minerals assemblage in the oasis area of the Kaidu−Kongque River Basin is of the illite−illite/smectite mixed−layer mineral−chlorite type. Clay minerals play a significant role in enhancing soil nutrient levels and immobilizing heavy metal elements through adsorption, thereby improving soil quality.